# 15hp yamaha



## Un-shore (Sep 27, 2007)

What width is your boat and how much weight are we talking. Actuall there are many factors, we need more info like  shaft length, running condition. pics would be great too.


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## OffShoreSkiff (Jun 28, 2009)

Its a short shaft. 4ft width Its seems to be in great running condition. When its on plane at WOT she prolly does 20-25. Its just the low speed take off. Not Sure which route to take next. Do I need a Service maybe? It starts right up one pull.


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## Brett (Jul 16, 2008)

Sounds like your top end is okay.
I think you just need to move some weight forward to balance the load in the hull.
Otherwise she'll squat on takeoff and be hard to plane


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## paint it black (Nov 3, 2007)

> Sounds like your top end is okay.
> I think you just need to move some weight forward to balance the load in the hull.
> Otherwise she'll squat on takeoff and be hard to plane


That skiff looks huge for a 15....
my trihull is 13'8 and is rated for a 50hp.
I got a 40 on it and it flies.


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## mark_gardner (Mar 18, 2009)

sounds like either you need to move some weight forward or maybe some more power like a 25 hp.,  prop look ok? whats the boat rated for? never mind i see shes rated for a 10 :-/ try moving some weight forward first and see what happens


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## WhiteDog70810 (May 6, 2008)

How heavy is that hull?  My first impression is that a 12 ft boat should fly with a 15 hp motor, but then I saw your picture.  That style of hull usually isn't light weight and adding a second person and gear probably pushes the weight past optimum performance parameters.  20-25 mph seems like reasonable performance for a 15 hp on a heavy (my assumption) 12 ft boat with one person and gear.  If the hull is ultralight and you weigh 150# and carry minimum gear, there might be a problem with the motor, but if that is not the case, I suspect your motor is fine.  

Definitely balance the load from bow to stern. Consider trim tabs or a Dolfin-type thing.  Either will help get the bow down on the hole shot which allows a small motor to work on pushing the hull forward over the water instead of pushing the hull up out of a hole.  I have used a Dolfin and found it to work very well, but some feel it adds too much drag and reduces top speed.  I never noticed that effect myself.  The cavitation plate ultimately fractured through the bolt holes, but I can't guarantee we didn't hit something.  No one else has reported that problem.  Adjustable trim tabs are the gold standard, but they are more expensive.

Sounds like the manufacturer was being overly cautious when he wrote up the hp rating.  I couldn't find hull weights or capacities on the Caprice website, but for comparison, a similar boat is a Carolina Skiff JV13.  It weighs around 413#, carries around 655# and is rated for 30 hp.  

Nate


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## OffShoreSkiff (Jun 28, 2009)

Here is the plate ratings. The boat weighs appx 500 lbs. I weigh 190. The Dol-phin is just below or right at the bottom of the hull. Should that be lower or higher?


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## OffShoreSkiff (Jun 28, 2009)

And like someone mentioned. A 15hp on a 12ft boat should fly. Even If im solo in the boat bass fishing. No cooler, livewell, anchor, nothing. Just my 190 the 3 04 gallons of gas i need to get through the trip and my deep cycle battery. which prob weighs 90lbs. damn maybe i need a smalller battery???


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## Un-shore (Sep 27, 2007)

That fin/motor should be higher. You will need to jack the motor up at least a couple inches.


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## MATT (Apr 30, 2007)

I have a 16ft caprice from Rivira Beach with a 50 merc 2 sk and that skiff flys after it is on plane. Feel like a very hevey hull till she planes out. But with power tilt and trim on the 50 it is no problem. You could cure this with Tiller Ext and move more to the midle of this skift. Good strong stable skift but no speed demon.


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## mark_gardner (Mar 18, 2009)

you think you could get ahold of the builder to see if you can get a bigger capacity plate in the event you move to more power? i had a boat once that the builder offered this to me but i was looking to sell in the near future and had no intentions of swapping motors


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## OffShoreSkiff (Jun 28, 2009)

I know this builder. We just to have the 16 in the same model with a 90 johnson and you couldnt not go fast.

As far as the motor height goes...Do i need to be up higher or down lower??


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## noeettica (Sep 23, 2007)

looks like an SE Sport foil ...They give no lift the sting ray Jr. and the doel fin Do
(Think I got that right )

Try a Doel Fin and if that works sell me the SE Sport ;-)

Also The Tiny Tach pitch approach thing ... What Prop You running ?

Guys correct me if I'm wrong but I'm thinking 9 1/4 x 10 or 10.5 Should be right for that Set-up ... But You may NOT break 20 But will run better all around

Dave


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## Un-shore (Sep 27, 2007)

you typically want your ventilation plate even or around 1" above the bottom of the hull. if it is lower than the bottom you start getting into drag issues which might be part of your problem. I had the same issue on my 13' gheenoe and a 9.9hp, I don't have a fin so i'm just guessing.

unless i'm wrong the fin is supposed to get you on plane faster and when on plane the fin is riding on top of the water. If the fin is lower than the bottom of your boat the fin is going to constantly try and lift the boat out of the water trying to get on plane.


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## paint it black (Nov 3, 2007)

Motor needs to be higher, and bigger.

I'm sorry, but a 10 wouldn't push that hull fast at all.

It looks like a tank.
and at 500lbs, that's heavy as hell for a 12ft.

You'd do fine with a 20-25hp.


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## WhiteDog70810 (May 6, 2008)

500#!!!  Your motor is just fine.  You, yourself and your shadow suck up almost 2/3 of your available payload (other than motor, fuel and battery). With your gear, I imagine you almost max out the weight just fishing solo. The extra weight of another person will mean your boat is technically overloaded and your motor is out of its league. I don't know why they under-rated that hull so badly. Does it do anything weird on plane?

If the hull weighs 500#, that means it is heavier than the comparable Carolina Skiff, which is rated to 30 hp.  While they are not the same hull, they are similar enough to draw the conclusion that you boat is underpowered no matter what the plate says.  I am sure you could tweak this motor to see some slight improvement by raising it or lowering or setting it back or playing with the prop or adding trim tabs, but in the end, you will still have an underpowered boat.  That 15 hp would be awesome on a 12-14 ft aluminum which weighed around 150-200#, but you need something bigger. 

You might want to look under your decks for water soaked flotation foam and wood. Maybe some of the weight isn't "factory". On the upside, that thing will take a beating. The old Rangers of that style and construction can still be seen on the water, despite being made in the `70s.

Nate


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## OffShoreSkiff (Jun 28, 2009)

> looks like an SE Sport foil ...They give no lift the sting ray  Jr. and the doel fin Do
> (Think I got that right )
> 
> Try a Doel Fin and if that works sell me the SE Sport ;-)
> ...



I may try a new fin. If i do ill give you first opertunity. Not sure about the prop. i also joined this site to find out some about it. I wanted to get a new one if needed. Or a better thrust.


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## OffShoreSkiff (Jun 28, 2009)

> you typically want your ventilation plate even or around 1" above the bottom of the hull. if it is lower than the bottom you start getting into drag issues which might be part of your problem. I had the same issue on my 13' gheenoe and a 9.9hp, I don't have a fin so i'm just guessing.
> 
> unless i'm wrong the fin is supposed to get you on plane faster and when on plane the fin is riding on top of the water. If the fin is lower than the bottom of your boat the fin is going to constantly try and lift the boat out of the water trying to get on plane.



So i definatly need to get it up a little. Maybe a jackplate?


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## OffShoreSkiff (Jun 28, 2009)

Im guessing 500#. Me and the old man that makes these boats picked it up and walked it on the trailer. one on either side. Me and my buddy 190 and 165 fish and usually with the bailtwell loaded with maybe 10-15 gallons of water it takes maybe 20 - 30 seconds to get on plane. and thats only if its flat water. Or with the current. I mean i go out to 500+ ft of water by myself and a full load. its just getting on plane takes a while.


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## TomFL (Oct 2, 2007)

Travis, yes you need to move the motor up a bit. That cav plate, with the SE sport or whatever version of wing you are using, should be about level with the bottom of the boat, if not just above it. 

That won't cure everything but it will be a start as it will lessen the drag. 

-T


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## OffShoreSkiff (Jun 28, 2009)

http://www.boatownersworld.com/thmarine/minijacker.htm

Would this be sufficant?


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## OffShoreSkiff (Jun 28, 2009)

The boat only weighs *180 *lbs......


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## noeettica (Sep 23, 2007)

For a little more you can have a Bob's


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## OffShoreSkiff (Jun 28, 2009)

Where do I find these?


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## Gramps (Nov 1, 2007)

Travis where are you located? I might have something for you.


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## OffShoreSkiff (Jun 28, 2009)

West Palm. I found the bobs mini jack plate. Its adjustable, where as the th-marine is fixed. 

Im definately getting one of these. Hoping I can use you guys to direct me to the better choice. Thanks. I got offshore a lot so there will be a lot of turbulance.


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## Gramps (Nov 1, 2007)

Travis - You got a PM.


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## noeettica (Sep 23, 2007)

Scott UR All Right ...


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## flyfshrmn82 (Oct 12, 2007)

How about your RPM's at WOT? How long does it take to get up and running? What prop do you have on it?


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## Big_Fish (Dec 10, 2006)

I would not go any higher unless you add a jack plate 
Tom C makes a good one cheap!


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## OffShoreSkiff (Jun 28, 2009)

> How about your RPM's at WOT?  How long does it take to get up and running?  What prop do you have on it?



Not sure exactly, but at WOT while trying to get on plane it doesnt sound likje they are very high. Almost like its bogging down. ANd the within 20 seconds it picks right up and goes. I went out to 600ft yesterday and she blazed right out there all the wide open. Just getting on plane is the prob. Its the stock prop.


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## OffShoreSkiff (Jun 28, 2009)

Also on the transom there is only about 9 inches before it dips in and goes down abither 6 0r 7 to the bottem of the transom. How does this affect me mounting a jack plate??

Im looking to get the narrow model manual jack from bobs.


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## Gramps (Nov 1, 2007)

It looks like you have plenty of room to mount a JP. Bob's JP only needs about 8" vertical for the mounting bracket. And a Tiny Tach (www.tinytach.com) is an inexpensive tach and will be helpful in proper propping of your boat.

I can swing by sometime to help ya out, just let me know.


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## OffShoreSkiff (Jun 28, 2009)

I am going to get one of those tacs.


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## OffShoreSkiff (Jun 28, 2009)

Well i got a deal on this jack plate that i could not pass on so i grabbed it. 

Here are before and after pics. I think im getting into the right ball park now.


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## OffShoreSkiff (Jun 28, 2009)

AFTER


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## OffShoreSkiff (Jun 28, 2009)

AFTER.


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## OffShoreSkiff (Jun 28, 2009)

I test drove her today. Seems to be improved. I have not gone with a lot of weight yet. But did not feel sluggish at all. Only think the little fin above the cavitation plate sprays water out behind the boat. Not sure if that is supposed to be doing that or what. The cavitation plate is just under the water when im running WOT. I did manually trim the engine and it did not spray anymore, but at the trim it porposes .

any ideas??


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## Brett (Jul 16, 2008)

When you find the point at which she porpoises,
then go back down 1 setting, that's as good as it gets.

Unless you feel like spending more money on adjustable trim tabs.


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## OffShoreSkiff (Jun 28, 2009)

Cool. Thats what i was thinking.


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## OffShoreSkiff (Jun 28, 2009)

> looks like an SE Sport foil ...They give no lift the sting ray  Jr. and the doel fin Do
> (Think I got that right )
> 
> Try a Doel Fin and if that works sell me the SE Sport ;-)
> ...



You interested in the fin still? 

What about this prop thing. Where is the best place to find?


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## OffShoreSkiff (Jun 28, 2009)

> looks like an SE Sport foil ...They give no lift the sting ray  Jr. and the doel fin Do
> (Think I got that right )
> 
> Try a Doel Fin and if that works sell me the SE Sport ;-)
> ...



This is the size prop im running.

9 1/4 x 10 1/2 - J. What does the "J" mean? 

I had Two guys full livewell and it definately gets up on plane better and she runs about 21.6 on the gps. It still takes about 5-10 seconds but im thinking thats good. Now I just want to work on the prop issue to see if I need something different there. Would more pitch give me more thrust at hole shot?


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## wcnfl (Nov 11, 2009)

Never over power a boat.


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## OffShoreSkiff (Jun 28, 2009)

Been out a handful of times now and she seems great. I can run on the flats and look over and see the bottom and the fish finder stops producing depth. And 25 mph On the GPS. Just need to get a Tiny Tach now And fine tune it.


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