# Motor height question



## BayStYat (Sep 12, 2012)

I have a Caimen with yamaha 50 2 stroke. I was told the motor height may be to low and that I should see the top fin of the cavitation plate. I this picture while running it's not visible. 

Thanks


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## Sublime (Oct 9, 2015)

My BT had a manual jack plate and a 50 etec and I could see the cav plate, but barely. Only one way to find out and that is to raise the motor up one bolt hole at a time until the prop starts blowing out. Then you can spend money getting a prop that won't. Then you can add a jack plate. I figure $1500 - $2000 later, you'll have it dialed in. lol.

But seriously, if it runs good where it is at, I'd leave it alone unless you just really need those last couple of inches to run shallower with. Your current set up will run better in chop, turn better and probably is more quiet than it will be raised up.


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## BayStYat (Sep 12, 2012)

Sublime said:


> My BT had a manual jack plate and a 50 etec and I could see the cav plate, but barely. Only one way to find out and that is to raise the motor up one bolt hole at a time until the prop starts blowing out. Then you can spend money getting a prop that won't. Then you can add a jack plate. I figure $1500 - $2000 later, you'll have it dialed in. lol.
> 
> But seriously, if it runs good where it is at, I'd leave it alone unless you just really need those last couple of inches to run shallower with. Your current set up will run better in chop, turn better and probably is more quiet than it will be raised up.


Thanks buddy. I was really looking for more mph. Most other caimen's see 34-35mph. I can squeeze out 30-31 at 5300 rpms with same motor and prop


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## No Bait / Lures Only (Apr 10, 2011)

BayStYat said:


> Thanks buddy. I was really looking for more mph. Most other caimen's see 34-35mph. I can squeeze out 30-31 at 5300 rpms with same motor and prop


BayStYat,
Raise the motor up so the prop can ventilate, think you said you had a PT Prop. PT Prop will run much higher and allow you to optimize your max rpm and speed. Motor should rev up at first and then grab, try the higher hole settings and adjust the angle pin to mid hole. Vance Mfg has a Manuel Jack Plate that will allow easy adjustments to motor, $240.


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## BayStYat (Sep 12, 2012)

stephenchurch said:


> BayStYat,
> Raise the motor up so the prop can ventilate, think you said you had a PT Prop. PT Prop will run much higher and allow you to optimize your max rpm and speed. Motor should rev up at first and then grab, try the higher hole settings. Vance Mfg has a Manuel Jack Plate that will allow easy adjustments to motor.


Thank you. Yes its a PTSCB13.


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## No Bait / Lures Only (Apr 10, 2011)

BayStYat said:


> Thank you. Yes its a PTSCB13.


My little Spear Skiff has a 16" transom and I run the motor @19"+ high on the Vance Jack that I modded with aluminum plate for extra height adjustments. Originally only 3" verticle adjustment with Jack, so 1/2" aluminum plate attachment and teak board solved my issues with low rpms. Measure the opening between the sponsons for a clearance dimension and view the available jack plates, Or buy 1/2"- 3/4" aluminum plate and DIY.....


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## topnative2 (Feb 22, 2009)

Tip of the day...get ur motor vertical then put a floor jack under the skeg and raise or lower it.....of course take the bolts out.....and get a helper to steady everything.....usually the cav plate is 2 inches up to start with...

remember if u go to high your motor will cavitate in turns ...so test the height including turning


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## Vertigo (Jun 3, 2012)

Tip #2: Place blocks under the skeg. Raise and lower the motor by using the trailer jack. Start with the cav plate an inch above the keel.


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## topnative2 (Feb 22, 2009)

Vertigo said:


> Tip #2: Place blocks under the skeg. Raise and lower the motor by using the trailer jack. Start with the cav plate an inch above the keel.


I keep forgetting that one........


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## makin moves (Mar 20, 2010)

At 5300 rpms are you full throttle?


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## devrep (Feb 22, 2009)

with a non tunnel boat and a standard prop the anti cavitation plate should be slightly out of the water when running on plane. A tunnel hull with a hyper cupped prop, esp a 4 blade will be much higher. When I'm on plane my anti cavitation plate is at least 2 inches out of the water.


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## fishtrapper (Jun 6, 2009)

BayStYat said:


> I have a Caimen with yamaha 50 2 stroke. I was told the motor height may be to low and that I should see the top fin of the cavitation plate. I this picture while running it's not visible.
> 
> Thanks



My advise for anyone with a caimen with a 50 2 stroke yami.......raise it up!!!!!!!!

I use to run mine with the jackplate all the way up with no problems. I would run mine so high that the tips of the prop eventually got frosted from running out of the water. The yami would hold water pressure with no problems. Most people are amazed when they see how high you can run a motor up on a caimen without a tunnel hull.


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## BayStYat (Sep 12, 2012)

topnative2 said:


> Tip of the day...get ur motor vertical then put a floor jack under the skeg and raise or lower it.....of course take the bolts out.....and get a helper to steady everything.....usually the cav plate is 2 inches up to start with...
> 
> remember if u go to high your motor will cavitate in turns ...so test the height including turning


thank you sir


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## BayStYat (Sep 12, 2012)

devrep said:


> with a non tunnel boat and a standard prop the anti cavitation plate should be slightly out of the water when running on plane. A tunnel hull with a hyper cupped prop, esp a 4 blade will be much higher. When I'm on plane my anti cavitation plate is at least 2 inches out of the water.


wow mine is at least 2 inches below the water


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## BayStYat (Sep 12, 2012)

makin moves said:


> At 5300 rpms are you full throttle?


5300 rpms at 31mph
5500 rpms at 31mph trimmed out before cavitation


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## BayStYat (Sep 12, 2012)

fishtrapper said:


> My advise for anyone with a caimen with a 50 2 stroke yami.......raise it up!!!!!!!!
> 
> I use to run mine with the jackplate all the way up with no problems. I would run mine so high that the tips of the prop eventually got frosted from running out of the water. The yami would hold water pressure with no problems. Most people are amazed when they see how high you can run a motor up on a caimen without a tunnel hull.


how high? right now my cav plate is even with the keel


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## BayStYat (Sep 12, 2012)

topnative2 said:


> Tip of the day...get ur motor vertical then put a floor jack under the skeg and raise or lower it.....of course take the bolts out.....and get a helper to steady everything.....usually the cav plate is 2 inches up to start with...
> 
> remember if u go to high your motor will cavitate in turns ...so test the height including turning


thank you sir


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## Godzuki86 (Nov 30, 2013)

BayStYat said:


> wow mine is at least 2 inches below the water


That seems way to low. That could be your problem in gaining the extra speed. At least that's what I was told when setting my motor height up.


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## fishtrapper (Jun 6, 2009)

BayStYat said:


> how high? right now my cav plate is even with the keel


I would start at least 2 holes up from where you are now.

I ran the jackplate on 6 always and had the motor mounted on second hole I think


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## BayStYat (Sep 12, 2012)

Godzuki86 said:


> That seems way to low. That could be your problem in gaining the extra speed. At least that's what I was told when setting my motor height up.


thank you sir


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## BayStYat (Sep 12, 2012)

fishtrapper said:


> I would start at least 2 holes up from where you are now.
> 
> I ran the jackplate on 6 always and had the motor mounted on second hole I think


Ok, but I can only go one more hole up. that would be the last hole.


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## ifsteve (Jul 1, 2010)

Boat is just too slow.....time to move on to a different boat.....lol

Seriously just raise it up to the last hole and then run it. That will be the simplest and cheapest adjustment. If that doesn't get you to where you need then look at the other options.


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## sjrobin (Jul 13, 2015)

Bay, had the same problem with 18 Waterman and 70 HP two cycle. Last hole up still not great, then manual jackplate five inch set back, better but steering torque at certain trim, now the owner is finally going to micro jack plate. Good micro jack plate not available in 2005. Being hard headed is a benefit sometimes but not all the time.


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## BayStYat (Sep 12, 2012)

sjrobin said:


> Bay, had the same problem with 18 Waterman and 70 HP two cycle. Last hole up still not great, then manual jackplate five inch set back, better but steering torque at certain trim, now the owner is finally going to micro jack plate. Good micro jack plate not available in 2005. Being hard headed is a benefit sometimes but not all the time.


Thank you sir. I plan on raising it to the top and leaving it alone. It would be nice for the extra mph but not gonna spend more money for just a few.


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## YnR (Feb 16, 2015)

topnative2 said:


> Tip of the day...get ur motor vertical then put a floor jack under the skeg and raise or lower it.....of course take the bolts out.....and get a helper to steady everything.....usually the cav plate is 2 inches up to start with...
> 
> remember if u go to high your motor will cavitate in turns ...so test the height including turning


Not to derail this thread but do you have to worry about breaking the skeg doing this?


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## permitchaser (Aug 26, 2013)

We would like to hear if what you do works


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## BayStYat (Sep 12, 2012)

permitchaser said:


> We would like to hear if what you do works


defiantly raising it to the next hole up (highest possible) and see what happens.


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## topnative2 (Feb 22, 2009)

YnR said:


> Not to derail this thread but do you have to worry about breaking the skeg doing this?


Nope...as long as ur vertical


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## Godzuki86 (Nov 30, 2013)

topnative2 said:


> Nope...as long as ur vertical


This. "Skeg stong like bull!"


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## BayStYat (Sep 12, 2012)

spoke to Adam at East Cape and we looked at the cav plate in relation to the hull and its where Adam said its ideal. We decided to go from a 13 pitch to a 14 pitch in the prop. I dropped it off to have it repitched. Thank you for all your insight.


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## No Bait / Lures Only (Apr 10, 2011)

BayStYat said:


> spoke to Adam at East Cape and we looked at the cav plate in relation to the hull and its where Adam said its ideal. We decided to go from a 13 pitch to a 14 pitch in the prop. I dropped it off to have it repitched. Thank you for all your insight.


What rpm did you finally turn?


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## BayStYat (Sep 12, 2012)

stephenchurch said:


> What rpm did you finally turn?


5100 with the 13 was the most speed I could get 30-31


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## devrep (Feb 22, 2009)

BayStYat said:


> 5100 with the 13 was the most speed I could get 30-31


I don't get it. If you're only getting 5100 with a 13 you're going to get like 4750 with a 14, Shouldn't that motor be turning 5500 or more?


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## BayStYat (Sep 12, 2012)

devrep said:


> I don't get it. If you're only getting 5100 with a 13 you're going to get like 4750 with a 14, Shouldn't that motor be turning 5500 or more?


5500 is the top rpms from my understanding.
Also I can get more rpms (5400) but I have to trim up more and don't gain anymore speed


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## topnative2 (Feb 22, 2009)

Try cupping the 13


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## BayStYat (Sep 12, 2012)

topnative2 said:


> Try cupping the 13


better than pitching to 14?


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## topnative2 (Feb 22, 2009)

me thinks that the 13 was giving u more rpm which would be better to put a cup in and it should give u some lift w/o a lot of trim....the cup will give u more bite w/o "losing "rpm.....hopefully

the lower the pitch the higher the rpm in all cases w/ the same prop.....does not necessarily mean more mph.....theoretically , u can get more speed increasing pitch while lowering rpm...all depends on the boat ....

putting a cup in a prop gives it more bite at the end of the revolution......not pushing a lot of useless water....a good prop shop should be able to figure it out what u need


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## devrep (Feb 22, 2009)

without reading thru all of this again have you tried some props with different characteristics?


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## BayStYat (Sep 12, 2012)

topnative2 said:


> me thinks that the 13 was giving u more rpm which would be better to put a cup in and it should give u some lift w/o a lot of trim....the cup will give u more bite w/o "losing "rpm.....hopefully
> 
> the lower the pitch the higher the rpm in all cases w/ the same prop.....does not necessarily mean more mph.....theoretically , u can get more speed increasing pitch while lowering rpm...all depends on the boat ....
> 
> putting a cup in a prop gives it more bite at the end of the revolution......not pushing a lot of useless water....a good prop shop should be able to figure it out what u need


should i add cup to the 14?


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## BayStYat (Sep 12, 2012)

devrep said:


> without reading thru all of this again have you tried some props with different characteristics?


I havent. only ran a SCB313 so far


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## jmrodandgun (Sep 20, 2013)

Does Powertech still let you try different props if you buy one from them? They are in in North La so shipping to you should be quick and easy. Might be worth giving them a call and asking.


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## topnative2 (Feb 22, 2009)

BayStYat said:


> should i add cup to the 14?


if u have already re-pitched the prop and are happy ...??????....rpm will tell the story..personally i would rather have a cup put into the prop to hit the mark rather than move up in pitch........so many variables ....talk to the boat manufac or other owners whoa have done the work

for practical purposes u will only get so much performance out of a small motor.....a different designed prop could be be better....u are pretty close to max. rpm w/ what u have.....don't get bogged down in it..... rather have a great mid-range than a top end any day of the week.......enjoy the boat....ditto


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## BayStYat (Sep 12, 2012)

topnative2 said:


> if u have already re-pitched the prop and are happy ...??????....rpm will tell the story..personally i would rather have a cup put into the prop to hit the mark rather than move up in pitch........so many variables ....talk to the boat manufac or other owners whoa have done the work
> 
> for practical purposes u will only get so much performance out of a small motor.....a different designed prop could be be better....u are pretty close to max. rpm w/ what u have.....don't get bogged down in it..... rather have a great mid-range than a top end any day of the week.......enjoy the boat....ditto


Thanks Top

I spoke to east cape and they recommended the 14p. I havent had it re pitched yet. its at the shop now.


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## topnative2 (Feb 22, 2009)

excellent....now enjoy the boat...it is a good one


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## No Bait / Lures Only (Apr 10, 2011)

topnative2 said:


> excellent....now enjoy the boat...it is a good one


Bay,
what rpm did you get to? what prop? remember if rpm is low, have to go with a lower pitch prop to raise rpm.......


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## BayStYat (Sep 12, 2012)

stephenchurch said:


> Bay,
> what rpm did you get to? what prop? remember if rpm is low, have to go with a lower pitch prop to raise rpm.......


I have not tried the 14 yet. I dropped off at the shop. with the 13 I got 5100 rpms at 30-31 mph


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## Whiskey Angler (Mar 20, 2015)

I have always achieved top speed on my boats, past and present, big and little, by lowering the motor height to the lowest setting or close to lowest and then trimming up until I hit the engine's prime wot rpm (usually 150-250 rpm below max rpm).
By doing this, you maximize your trim and maintain decent prop "grip" while lifting the bow which minimizes the amount of hull in the water. I should mention I have always run Jack plates so I can bury the motor when it's time to boogie, and Jack up when running slower through shallow water.

So....my recommendation.....Jack down and trim up.


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## BayStYat (Sep 12, 2012)

Whiskey Angler said:


> I have always achieved top speed on my boats, past and present, big and little, by lowering the motor height to the lowest setting or close to lowest and then trimming up until I hit the engine's prime wot rpm (usually 150-250 rpm below max rpm).
> By doing this, you maximize your trim and maintain decent prop "grip" while lifting the bow which minimizes the amount of hull in the water. I should mention I have always run Jack plates so I can bury the motor when it's time to boogie, and Jack up when running slower through shallow water.
> 
> So....my recommendation.....Jack down and trim up.


Thank you sir


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## BayStYat (Sep 12, 2012)

I spoke to the prop shop and we decided to add cup to the 13 pitch. Hopefully it will allow me to gain mph at 5400 rpms. As of now no difference in speed from 5000 to 5400. I get slip from 5000 to 5400 from trimming up.


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## browndogrods (Oct 21, 2010)

BayStYat said:


> I havent. only ran a SCB313 so far


Not much help bc I don't know my rpm, but I'm running a beat up nreb14 on a nonliner caimen tiller with the same motor... Tm and battery up front, I'm in the 31-33 range. I just put a scb13 on it but have yet to run it.


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## devrep (Feb 22, 2009)

according to the manual that motor makes peak hp at 5K rpm.


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## BayStYat (Sep 12, 2012)

devrep said:


> according to the manual that motor makes peak hp at 5K rpm.


Interesting


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## BayStYat (Sep 12, 2012)

browndogrods said:


> Not much help bc I don't know my rpm, but I'm running a beat up nreb14 on a nonliner caimen tiller with the same motor... Tm and battery up front, I'm in the 31-33 range. I just put a scb13 on it but have yet to run it.


Your boat will be much lighter than mine. Should run above 35 with the SCB


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## topnative2 (Feb 22, 2009)

BayStYat said:


> I spoke to the prop shop and we decided to add cup to the 13 pitch. Hopefully it will allow me to gain mph at 5400 rpms. As of now no difference in speed from 5000 to 5400. I get slip from 5000 to 5400 from trimming up.


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## No Bait / Lures Only (Apr 10, 2011)

BayStYat said:


> Your boat will be much lighter than mine. Should run above 35 with the SCB


Bay St Yat,
sound like your 50 Yamaha need a service trip to HydroTec for a Stage Upgrade, you don't have to go to a 70........ Call Jon Wolfe @ Hydrotec


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## BayStYat (Sep 12, 2012)

stephenchurch said:


> Bay St Yat,
> sound like your 50 Yamaha need a service trip to HydroTec for a Stage Upgrade, you don't have to go to a 70........ Call Jon Wolfe @ Hydrotec


I did look into it and it does sound interesting. I need to find someone who can do the work.


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## GulfCoast (Jul 10, 2012)

Whiskey Angler said:


> I have always achieved top speed on my boats, past and present, big and little, by lowering the motor height to the lowest setting or close to lowest and then trimming up until I hit the engine's prime wot rpm (usually 150-250 rpm below max rpm).
> By doing this, you maximize your trim and maintain decent prop "grip" while lifting the bow which minimizes the amount of hull in the water. I should mention I have always run Jack plates so I can bury the motor when it's time to boogie, and Jack up when running slower through shallow water.
> 
> So....my recommendation.....Jack down and trim up.


just my little input if I may.......
I had tried this on the Caimen. did not like the results.had to raise to get the motor to get the most out of it. second to last hole with the 60 Suzuki and PT three blade prop. loved the four blade too. handling was killer and hole shot with ZERO bow lift.


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## No Bait / Lures Only (Apr 10, 2011)

BayStYat said:


> I did look into it and it does sound interesting. I need to find someone who can do the work.


Sid is capable to add components or send the complete motor to Hydrotec...


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## browndogrods (Oct 21, 2010)

BayStYat said:


> Your boat will be much lighter than mine. Should run above 35 with the SCB


Again, no tach but I finally got a chance to run the new prop today. Wrong prop for my setup. Maybe should have gone to a 14P. 31 was the max it could muster. I'm getting a 3-4 more mph with the beat up 14 I have. Betting the vendor won't exchange it, wondering it I can have the pitch changed.


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## BayStYat (Sep 12, 2012)

browndogrods said:


> Again, no tach but I finally got a chance to run the new prop today. Wrong prop for my setup. Maybe should have gone to a 14P. 31 was the max it could muster. I'm getting a 3-4 more mph with the beat up 14 I have. Betting the vendor won't exchange it, wondering it I can have the pitch changed.


thats exactly what i get with the scb13. hmmmm


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## BayStYat (Sep 12, 2012)

added cup to SCB13 and did not see much difference. Thoughts?


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## No Bait / Lures Only (Apr 10, 2011)

BayStYat said:


> added cup to SCB13 and did not see much difference. Thoughts?


What was the RPM with the new prop?


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## BayStYat (Sep 12, 2012)

Everything seemed the same. Rpm and speed


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## No Bait / Lures Only (Apr 10, 2011)

BayStYat said:


> Everything seemed the same. Rpm and speed


Can you raise the motor any higher?


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## devrep (Feb 22, 2009)

can you post a good photo of the cupping work?


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## BayStYat (Sep 12, 2012)

devrep said:


> can you post a good photo of the cupping work?


not sure if you can see the work.


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## devrep (Feb 22, 2009)

Looks pretty well cupped, I would think you would lose some rpm and gain some grip from that.


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## BayStYat (Sep 12, 2012)

devrep said:


> Looks pretty well cupped, I would think you would lose some rpm and gain some grip from that.


man i still got the same rpm, 5400


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## snooks2005 (Sep 15, 2015)

BayStYat said:


> man i still got the same rpm, 5400


sent you pm


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## No Bait / Lures Only (Apr 10, 2011)

snooks2005 said:


> sent you pm


can you raise your motor? if so it should increase rpm....


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## BayStYat (Sep 12, 2012)

stephenchurch said:


> can you raise your motor? if so it should increase rpm....


East cape said that the height is perfect. The cav plate should be even with the bottom of the hull and it's dead on.


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## No Bait / Lures Only (Apr 10, 2011)

Not saying anything negative, but until you try raising the cavitation plate above the bottom you won't know if the performance will improve. All of my three skiffs that I owned had the plate above the bottom Spear was 1 1/2" above, Shipoke was 2" above, Hoog was 2" above the pocket that is 4" higher than the bottom/pad. Have to raise until it starts to blow out, run the boat and see if the prop bites and then grabs. Each boat requires tweaking the height. The builder is not tweaking the height for the exceptionally detail buyers, probably the general buyers of the skiffs. This is my theory and I have always gotten exceptional performance from all the skiffs.


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## BayStYat (Sep 12, 2012)

stephenchurch said:


> Not saying anything negative, but until you try raising the cavitation plate above the bottom you won't know if the performance will improve. All of my three skiffs that I owned had the plate above the bottom Spear was 1 1/2" above, Shipoke was 2" above, Hoog was 2" above the pocket that is 4" higher than the bottom/pad. Have to raise until it starts to blow out, run the boat and see if the prop bites and then grabs. Each boat requires tweaking the height. The builder is not tweaking the height for the exceptionally detail buyers, probably the general buyers of the skiffs. This is my theory and I have always gotten exceptional performance from all the skiffs.


Sound great. I got your pm. Thank you sir I can only go up one more hole.


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## sjrobin (Jul 13, 2015)

Correct Stephen. In a previous post on this topic I outlined the steps we took on a new at the time Waterman 18 with 70 HP two stroke. Original install by T Gordon was no jackplate, with cav plate even with hull but to reduce torque and improve shallow water performance we moved to max height, better, then manual jackplate set even higher four inch set back even better performance. During this process no loss or gain in speed just less torque and better shallow water performance. Speed after a certain point is dependent on hull design and weight. At no point did we consider changing the prop.


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## ifsteve (Jul 1, 2010)

Starting to sound to me like a jackplate would have been cheaper and a lot easier in the long run?


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## Ron_D (May 5, 2013)

BayStYat said:


> Sound great. I got your pm. Thank you sir I can only go up one more hole.


Sent you a PM


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## jfboothe (Dec 19, 2012)

Not sure if this helpful or if you have seen it but this is pretty good info on motor height. http://www.veradoclub.com/index.php?topic=137.0


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## BayStYat (Sep 12, 2012)

jfboothe said:


> Not sure if this helpful or if you have seen it but this is pretty good info on motor height. http://www.veradoclub.com/index.php?topic=137.0


Well dam. Thanks for that info. Going to raise it


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## sjrobin (Jul 13, 2015)

Let us know if the raised motor works for you Bay St Yat. The set back from a jack plate will also improve performance if your skiff has sponsons. The light weight Atlas micro is ideal and enables you to trim for various loads and water conditions. Money well spent for a small skiff.


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## Vertigo (Jun 3, 2012)

All this screwing around with height, pitch, cup, etc. may be in vain. How are you measuring speed? Is your GPS set to mph or to knots?


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## BayStYat (Sep 12, 2012)

Vertigo said:


> All this screwing around with height, pitch, cup, etc. may be in vain. How are you measuring speed? Is your GPS set to mph or to knots?


its mph. gonna move the motor up one and be done. my brothers caimen is set at a height where you can see the cav plate. mine is under water.


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## jackschuh (Nov 3, 2014)

On my Fury I have a jack plate but when running the best setting has the cav plate at least 2" up.


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## devrep (Feb 22, 2009)

both of mine run with the plates up out of the water, on the tunnel hull of course its way up. don't expect any miracles though, maybe 2 mph or so I bet.


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## Vertigo (Jun 3, 2012)

Calculated prop slip for a true 13 pitch prop at 5100 rpm and 31 mph is 8%. 

Those are pretty good numbers and may be hard to improve upon. Maybe getting some weight out of the boat and/or checking the bottom for a hook or other irregularities could add a few mph. Raising the motor one hole may help, but probably not that much.


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## LowHydrogen (Dec 31, 2015)

Curious about this, how did it turn out as far as performance gained, and where did the cav plate end up when running?


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