# Why's it Taking So Long to Plane?!



## rkmurphy (Nov 2, 2008)

Okay so I'm really starting to miss my Merc 25 2 stroke that planed the boat in a boat length or two with no jackplate. But, here's the deal:

When I first got my 25 EFI, it planed fairly well with 2 people. 9.5 x 11P prop, jackplate raise 1/4", and motor tilted "level".

Now, it's taking me forever to get on plane and I'm starting to get pissed since I can't figure out what the problem is. So here's my current setup, in detail, and maybe some of you will have some ideas...

- Jackplate lowered 1/4" to reduced cavitation
- Cavitation plate 1.5" above bottom of hull
- Cavitation plate, when motor is tilted on the "level" pin, is tilted at a very slight downward sloping angle
- 9.5 x 10P prop with very minor cupping
- TomC trim tabs angled slightly downward (~0.5" below bottom of hull)

Now for what's in my boat, in detail:
- Rear:
- 3 gallon gas tank
- Starting battery in starboard corner
- Casting/poling platform on rear deck
- Life-jackets and spare prop in port rear deck hatch
- Middle:
- Cooler w/ 10 lb bag of ice
- Front:
- Trolling motor on removable bracket mounted on port side of front deck
- Dry boxes, mushroom anchor, and cast net on starboard side under front deck
- Misc. stuff (<3-4 lbs total) on port side under front deck
- Trolling motor battery mounted in middle under front deck

I think that's everything...

A couple of things I'd like to note:

I'm getting some weird spray while under way and on plane coming from what looks like the bottom of the jackplate or the lower unit. A forum member posted a similar occurrence not too long ago.

I don't seem to be "hopping" on plane but more like "crawling" on plane. I get very little bow rise, if any. If the passenger moves to the back, it takes way longer to get on plane (bow goes way up...), so that didn't help.

Anyone have the fix-all answer? :-/


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## Brett (Jul 16, 2008)

Too bad you live on the opposite coast.
We could have an enjoyable day with wrenches
hydraulic jack, handheld gps and a couple of props.
We already know that 25 hp is 25 hp.
We already know how fast your hull can go.
You've been adding and changing things.
Now you get to figure out what's different.
Is the prop hub slipping? Is the prop ventilating?
Wrong engine angle? It'll be something simple.


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## TomFL (Oct 2, 2007)

Start with the simple; are you getting proper RPM's at WOT? 

If you've lost RPM's at full throttle you've lost horsepower somewhere. You've mentioned some overheat buzzer issues recently, etc. which may have the motor running in safe mode or something????

If you're still getting full RPM's at WOT then it's something simple. 

-T


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## rkmurphy (Nov 2, 2008)

> Is the prop hub slipping?


One prop is brand new and the other was just reconditioned. They tested the hub and it was still good.



> Is the prop ventilating?


It wasn't too bad and when the jackplate was 1/4" and 1/2" up. Since I've lowered it, I haven't noticed any at all.



> Wrong engine angle?


There's really only one good engine angle for this thing, it seems like. It's either a very very slight downward angle (where it's at now), an obvious downward angle, or a pretty heavy upward angle.

Wish I was closer to that coast, too!


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## Brett (Jul 16, 2008)

Check that tachometer the next time you go out.
If you're pulling high end rpm's, then something you've added
has messed up your ride. Most times it's too much load at the stern.
When sitting still in the water, the hull should be level in the water.
That 2nd chine should be parallel with the water's surface.
If you're bow high, move your passenger forward!


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## rkmurphy (Nov 2, 2008)

> are you getting proper RPM's at WOT?
> 
> If you've lost RPM's at full throttle you've lost horsepower somewhere. You've mentioned some overheat buzzer issues recently, etc. which may have the motor running in safe mode or something????
> 
> ...


Just ordered a tiny tach. Hopefully it'll be here by the end of next week.

I haven't had any overheating problems since I replaced the thermostat. Knock on wood...

If it runs in safe mode, it won't let me go past 2000 RPM, I think. I'll have to look. Plus, it obnoxiously beeps at me the whole time, which I'm okay with as long as it keeps the motor from blowing up


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## Brett (Jul 16, 2008)

Are you doin' a Curtis?
You gotta pull the anchor pin up before leaving!


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## Frank_Sebastian (Oct 15, 2007)

One thing you might check is look for fishing line in the prop hub? Also check for a bent prop. A bend that you can hardly see will have a big effect on performance.

Best regards,
Frank_S


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## rkmurphy (Nov 2, 2008)

> Are you doin' a Curtis?
> You gotta pull the anchor pin up before leaving!


I actually about did this today, sadly...



> One thing you might check is look for fishing line in the prop hub? Also check for a bent prop. A bend that you can hardly see will have a big effect on performance.
> 
> Best regards,
> Frank_S


Both props are brand new. I just switched props yesterday and the seal looked fine. No fishin' line!


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## FSUfisher (Jul 16, 2007)

Thinking outside the box, have you checked your hull lately for water intrusion? The CSs are notorious for having water get in the foam cavities in the bottom of the hull. I have an old hole from a previous transducer mount on my stern that I open up every once in awhile to let the water out. No wood, no foul though! Also, where is the gas tank, and would it being full or empty have an effect? Mine's 13 gallons and makes a difference when full.
BTW, I get the same spray you talk about; don't know if it is the hull design or what. Mine actually comes into the boat after some time.


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## rkmurphy (Nov 2, 2008)

My spray doesn't come into the boat, luckily.

I thought about the water intrusion issue, too. I just don't see what could allow that amount of water in. I've only got 4 holes in the deck and then the ones Tom C drilled for the trim tabs. But, I was there and he sealed them pretty good with some 4200. Other than that, I just don't see how any significant amount of water could get in...


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## DuckNut (Apr 3, 2009)

After you get on plane are you getting the same speed?

Someone above mentioned water, if you have a hole in the hull and water got in you could be carrying a couple hunderd extra pounds and never see it.


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## rkmurphy (Nov 2, 2008)

> After you get on plane are you getting the same speed?
> 
> Someone above mentioned water, if you have a hole in the hull and water got in you could be carrying a couple hunderd extra pounds and never see it.


Yeah it seems like I'm getting the same speed. I've only tested it once since I first got the motor but that was when I was testing a different prop. 1.5" down in pitch dropped my top speed 4 mph (25 mph). I've since gotten a prop 0.5" up in pitch and down 0.25" in diameter.

I've checked the hull and I'm hole-less (other than the above mentioned sealed holes). I guess I could drill a hole in the bottom to see if water comes out but I'm really not wanting to drill any holes in the skiff, especially below the water line.


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## DuckNut (Apr 3, 2009)

Don't drill a hole...take it to a scale. Unload it and then have it weighed. MFG can tell you how much hull, trailer and motor weigh. Add it up and guestimate the incidentals that are bolted down and you will come up with a fair number to match agaist the scale. The last time I weighed one the truck stop did it for free but I gave the guy $10. I have also used a scrap metal yard. Best way is you and a buddy go and get it weighed and then dump the boat in the water and have your buddy stay with the boat and go get weighed again. Just don't forget to add your buddy's weight back in and don't let him BS you about his weight.

But you also need to find out about the rpm's.


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## rkmurphy (Nov 2, 2008)

> Don't drill a hole...take it to a scale.  Unload it and then have it weighed.  MFG can tell you how much hull, trailer and motor weigh.  Add it up and guestimate the incidentals that are bolted down and you will come up with a fair number to match agaist the scale.  The last time I weighed one the truck stop did it for free but I gave the guy $10.  I have also used a scrap metal yard.  Best way is you and a buddy go and get it weighed and then dump the boat in the water and have your buddy stay with the boat and go get weighed again.  Just don't forget to add your buddy's weight back in and don't let him BS you about his weight.
> 
> But you also need to find out about the rpm's.


The closest truck stop I know of around here is 15-20 miles away...

What are the chances I'd get that much water in the hull, anyways? Especially with such few, properly sealed holes...


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## firecat1981 (Nov 27, 2007)

with that 4-stroke you might have to much weight in the rear, I'd try moving the battery up front and see how that works or find some wieghts and add 100lbs to the front. Did the dealer dyno test the motor? I'm guessing not, but it's possible after the over heating issues you aren't getting full power anymore. I had an old chevy that did that, ran smooth and fine, but never had the get up and go like it did before. 
I'd bet its weight and setup though, I'd also try lowering the trim tabs, most boats I've seen have them hanging atleast 1.5 inches below to help planing, and go back to your old jackplate setting.


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## Brett (Jul 16, 2008)

Why's it Taking So Long to Plane?
Time spent getting through security!
You'll have to take that up with TSA!

                       [smiley=happy.gif]


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## pole_position (Dec 5, 2009)

If you have TnT trim the motor all the way down then raise it as you come up on plane.I have never had trim tabs but I would think they would work the same way.

I have the same wierd spray comming up between the stern and JP, also have a very slight cavitation issue so I dropped it 1/2" so Im gonna see if that cures it next time out.


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## DuckNut (Apr 3, 2009)

If I am not mistaking that hull is a foam sandwich. Foam between the floor and hull. Get a hole in there and it will fill that cavity with water.

I could be wrong but you would know best. 

Just a thought RK.


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## rkmurphy (Nov 2, 2008)

After a certain year, all CS's used closed cell foam. Granted, it can still fill with water. However, as I said before, there are very few holes drilled in my skiff and those that are are properly (maybe even excessively...) sealed.

I'm going to start investigating the motor a little today. Check plugs, compression, oil, etc. Oil is brown in color but still looks pretty good and is definitely full. About to check the plugs and compression now.

I also adjusted my tabs up to level with the bottom of the skiff. Hopefully that'll help to give me some bow rise to "hop" on plane a little better.

Here are some comparison pics of how a J16 with a 4 stroke 25 "should" sit in the water:

Other J16-->









My J16-->


















Seems to be about right...

This is frustrating


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## FSUfisher (Jul 16, 2007)

Was that a dual console J16?


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## rkmurphy (Nov 2, 2008)

> Was that a dual console J16?


Haha yes. It's a guy's skiff from the Carolina Skiff Owners forum.

One thing I'd like to point out...it seems the skiff throws a considerably bigger wake than it did with my 2 stroke. I'm not sure how it was when I first got the EFI...it just ran and that's all I knew and cared about. The 2 stroke felt as if it was gliding on top of the water...


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## noeettica (Sep 23, 2007)

I have a weird idea ... Weigh the boat


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## flightmedicjh41 (Mar 26, 2009)

You went from a 2 stroke to a 4 stroke? I have had issues with mine not planing or taking to long to plane. I have the J14 with a 15 merc 4 stroke. You have a 25 4 stroke on a J16 right? I think my issue is the motor. I would love to know what you find out.


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## noeettica (Sep 23, 2007)

Sorry That was already suggested ...lol

Stingray may help ...

but do the Tinytach thing first ...

and more Importantly Only change 1 thing at a time !

dave


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## choppercity47 (Jul 30, 2007)

I'd set the bobs jackplate all the way back #1


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## sh006177 (Jan 24, 2010)

rkmurphy, I have a 2009 j16 hull and merc 25 4 stroke. I had the same problem as you the boat would go 30mph but would take forever to get on plane. I put on the smart tabs and now it jumps on plane right away. I did lose 1mph..


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## rkmurphy (Nov 2, 2008)

Thanks all.

I went to go check on everything yesterday (plugs, etc.) but I can't seem to find my little tool kit that came with the motor or my compression tester. Weird...

Anyhow, I raised the jackplate up to the original position (actually about 0.25" above it...Bob's manual jackplate is a nightmare to adjust...) so that puts the front of the cavitation plate ~2" above the bottom of the hull and the back of the cavitation plate ~1" above the bottom of the hull.

Today, I'm going to get the skiff weighed to check for possible water intrusion. An unlikely occurrence but, still very possible.

Another theory that was put on the table is that the motor may be sucking some air. I find this to be very plausible as I noticed that the primer bulb, after sitting for even short periods of time (i.e. 30 minutes sometimes), will completely deflate. Even once on Saturday to the point where the motor wouldn't start until I pumped it (this was after running all day, too).

The trim tabs have been moved back to level with the hull. If I get a chance to get on the water today, I'll bring some tools and see what happens.

Wish me luck and pray there's not water in this d*mn hull!


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## rkmurphy (Nov 2, 2008)

Well, I just got back from the weigh station.  I didn't have the ability to drop the boat off and weigh the truck and trailer without the boat so, I did the next best thing.  I was by myself so I took 3 different weights.

Weight of just trailer with boat on it but still attached to truck: 1320 lbs

Weight (assuming I'm looking at the "Gross Weight" on the printout) of entire rig (boat, motor, trailer, and truck): 5,740 lbs

Weight of truck only: 4,280 lbs

Using the last 2 measurements, I made the following calculation:

5,740 gross weight total rig - 4280 gross weight truck only = 1,460 lbs - 172 lb motor - 12 lb jackplate - 5 lb trim tabs - (35lb battery x 2) - 35lb trolling motor - 10 lb misc = 1,156 lbs

I'm getting 2 different "quotes" on the weight of the trailer.  Continental said approximately 400lbs while the registration for the trailer says 180lbs.

So that'll give me either 756lbs or 976lbs for the bare hull with front and rear decks.

I'll try to get the weights on the decks and see how that plays out...

What are your thoughts on the trailer weight situation?


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## DuckNut (Apr 3, 2009)

If that is the trailer in your picture (which is nearly identical to mine) probably 180. If you can pick up and shift the trailer by yourself then it is most likely not the 400.


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## rkmurphy (Nov 2, 2008)

> If that is the trailer in your picture (which is nearly identical to mine) probably 180.  If you can pick up and shift the trailer by yourself then it is most likely not the 400.


That's what I was thinking...this isn't leaving me with a good feeling in my stomach...


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## FSUfisher (Jul 16, 2007)

If by some chance you do have water in the hull, don't worry. It's really not a big deal. [smiley=1-thumbsup3.gif]


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## noeettica (Sep 23, 2007)

I Know this aint funny But I could NOT resist ...

http://www.youtube.com/watch?v=4CFe20MW_as


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## firecat1981 (Nov 27, 2007)

I wouldn't put much thought in that weight calculation. Unless you strip everything down to the bare hull then i fail to see how this can possibly be accurate. There is just to many variables like did you have any gas in the boat? how much do your batteries really weigh (my battery is closer to 50lbs+ for my group 29)? are your decks custom? do you know how much they weighed if so? how much extra hardware is in it? lights?

if you are really paranoid about water intrusion why not take off one of the trim tabs and see if water comes out of the screw hole? if it does then you know your issue, personally I'd think it's more of a set up issue. I'd go back to basics, take everything off and just bolt the motor on and see if it planes well, then add one thing at a time until you get the results you want.



> so that puts the front of the cavitation plate ~2" above the bottom of the hull and the back of the cavitation plate ~1" above the bottom of the hull.


ok this confuses me, why isn't your motor in the level position? the only reason for having a motor tilted out of level is if you don't have tabs or a jack plate to help adjust it running right? I would set the tabs all the way up so they are not functioning, level the motor, and lower the jack plate so the cavitation plate is equal or close with the hull bottom and give it a shot. This is kinda like stripping the boat down just without the work, then adjust one thing at a time until it works. I'm sure there is a simple solution, keep yer chin up buddy.


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## rkmurphy (Nov 2, 2008)

> I wouldn't put much thought in that weight calculation. Unless you strip everything down to the bare hull then i fail to see how this can possibly be accurate. There is just to many variables like did you have any gas in the boat? how much do your batteries really weigh (my battery is closer to 50lbs+ for my group 29)? are your decks custom? do you know how much they weighed if so? how much extra hardware is in it? lights?
> 
> if you are really paranoid about water intrusion why not take off one of the trim tabs and see if water comes out of the screw hole? if it does then you know your issue, personally I'd think it's more of a set up issue. I'd go back to basics, take everything off and just bolt the motor on and see if it planes well, then add one thing at a time until you get the results you want.
> 
> ...


I have taken everything out of the hull except the following:

Motor, jackplate, trim tabs, 2 x group 24 batteries, and bilge pump

Carolina skiff has a similar rig setup on there website set at 570 lbs with stick steering and no rear deck. Taking that into account, I'll leave a 50lb margin of error.

The idea with taking off a trim tab has crossed my mind and, pending the results of tomorrow's weigh-in, I may do that.

I'm really not sure about the cavitation plate issue. But, it's as level as the motor will get. I just adjusted the tabs up to compensate and (again, pending the results of the weigh in) will see if that makes a difference.


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## TomFL (Oct 2, 2007)

I second the notion of the weight calculations not getting you anywhere. You're guessing, and garbage in equals garbage out when doing math!!

If the boat has always gotten up on plane slowly with the 4-stroke, chances are that's it. If it's been getting slower to get up on plane or your top speed has also been affected, you absolutely need to be looking for a problem. Find your compression tester and give the motor a once over. Have you checked your lower unit lube to be sure you're not full of water down there and spinning gears in soup?

As previously suggested I'd then start looking at water intrusion in the hull. The foam can and will hold tons of water. One small pinhole and it's gonna accumulate. 

Post a video of the boat getting up on plane here so we can all see if it's pig slow or just normal. 

-T


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## rkmurphy (Nov 2, 2008)

Well looks like we may have had a false alarm. 940lb with hull, motor, jackplate, trim tabs, removable trolling motor bracket, 2 group 24 batteries, front and rear decks, etc.

I got a chance to run the skiff with a buddy and it rides a lot better since the adjustments I made...still not like my 2 stroke, though! I'm getting 26-26.5 mph WOT with the 9.5 x 10P. I need to go back up to the 11P. I honestly think it planed better. I also noticed that the primer bulb is losing pressure so that'll have to be addressed.

I'll keep you all updated after I get the fuel line issue taken care of. Thanks for all of the help so far!


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## Brett (Jul 16, 2008)

;D Worry wart   ;D

Here I was thinking you might actually have a real problem to solve.
But all you needed to do was rearrange the furniture.


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## FSUfisher (Jul 16, 2007)

> Well looks like we may have had a false alarm.  940lb with hull, motor, jackplate, trim tabs, removable trolling motor bracket, 2 group 24 batteries, front and rear decks, etc.
> 
> 
> I got a chance to run the skiff with a buddy and it rides a lot better since the adjustments I made...still not like my 2 stroke, though!  I'm getting 26-26.5 mph WOT with the 9.5 x 10P.  I need to go back up to the 11P.  I honestly think it planed better.  I also noticed that the primer bulb is losing pressure so that'll have to be addressed.
> ...


Please let us know why the bulb is losing pressure when you figure it out. Since my ride is similar, it may help me diagnose my own bulb woes (I bought my boat that way). I'm just not motivated enough to troubleshoot my fuel line setup as it doesn't _seem_ to affect performance unless at a pretty high rpm.


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## Frank_Sebastian (Oct 15, 2007)

When you are running your engine the fuel pump is sucking the fuel through the bulb. It is normal for it to be soft in use. (not collapsed, just squeezable.)

Frank_S


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## Brett (Jul 16, 2008)

When you say the bulb is losing pressure,
do you mean it won't pump fuel to the engine until firm,
or do you mean after running a while it's squeezable?

:-?


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## rkmurphy (Nov 2, 2008)

I always thought the bulb was supposed to stay firm all the time...

It loses firmness pretty quickly when motor is off and when motor is running. Motor does still run, however. It does shut off at idle occasionally...


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## Brett (Jul 16, 2008)

The squeeze bulb operates by utilizing two one way valves.
Squeeze the bulb, and the out valve opens, the in valve closes.
Let go, the out valve closes, the in valve opens.
Once you've pressurized the line to the fuel pump
and filled the float bowl if it's carbureted, the fuel pump
on the engine does the rest of the work.
That means the pressure in the line drops, and the squeeze ball gets soft.
It doesn't remain firm. As long as no air is leaking into the fuel system, you're fine.


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## The_Skiff_Shop (Oct 28, 2008)

Even if you are water logged the boat should plane out - it will just will be slower. I've worked on several H2O logged CS's and the owners didn't even notice. 

Sounds like weight distribution based on your "bow rise" statement. Instead of moving stuff right off the bat, try taking about 200 lbs and putting it in the bow. Then move it around till the boat performs to your satisfaction. If it works, then redistribute your rigging and gear accordingly.


as always. just my .0000000000000000.5 sense


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## rkmurphy (Nov 2, 2008)

Got my Tiny Tach today and put 'er on. Cool little gadget! Pretty easy install, too.

I tested it in the driveway. I didn't realize motors idled at such a high RPM while warming up. I started at 1200-1300 and it was down to 990 before I shut it off. You learn something new everyday, I guess.

I'll get on the water this weekend and report back with some numbers.


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## Flyline (Mar 3, 2008)

The tinytach is awesome. So u can tweak it better with jackplate and the propeller to get the max. RPM range on your tinytach.


Man.... You spend more hours on the forum than u were on the water! ;D


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