15 hp mercury mouse hard to plain out

J

jetportdock

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I have a 2000 Mercury Mouse boat with a 15 Hp Mercury Motor. The boat is 10'5" feet long and weighs about about 350lbs. The motor runs good and once it plains out it will run around 24 mph. The problem is that with a low tank of fuel it will not plain out unless I throw my weight forward. I weight 210lbs. How to fix this without loseing top speed? Change Props? It currently has a 9"x10.5" would a 9" x 9" prop be better or do I need to go with a 9"x10" prop. How can a boat go 24 mph but a pain to plain out ?
 
Bondo

Bondo

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Re: 15 hp mercury mouse hard to plain out

problem is that with a low tank of fuel it will not plain out unless I throw my weight forward.
Click to expand...

Ayuh,... Sounds like it's starving for fuel, 'n consequently Down on power...
 
ONERCBOATER

ONERCBOATER

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Re: 15 hp mercury mouse hard to plain out

you have a weight distribution issue my friend.
what else is in the boat? move your heavier weights up to the front, batteries, fuel tank, fishing tackle.... perhaps GF or wife...10 1/2ft is aweful small for a 15hp.
anyhow as far as what prop you need, yours is likely fine, what RPM are you running with what prop at what speed....that is how you find out if your prop is right.

I would 1st move things about in the boat to the front, then possibly consider other options if redistribution of weight does not solve your issue.

other things to consider after moving your weight around would be venting props, trimtabs, and the accursed hydro for the engine (really a crutch 98% of the time)

What i think is happening is your weight is too far to the rear, your bow likely rises sharply while pushing a large (for the boat) wake, then as you lean fwd you are able to get on top of the wake and things improve considerably from there on. Correct?

Sean
 
J

jetportdock

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Re: 15 hp mercury mouse hard to plain out

I dont think that is it. The boat has little less then a 1/4 tank of fuel. Also the fuel tank is an 8 or 10 gallon fuel tank
 
ONERCBOATER

ONERCBOATER

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Re: 15 hp mercury mouse hard to plain out

fuel issue is a possibility, i still put my money on weight distribution. Can you rotate your tank to place the fuel pick up to the lower rear most point?

do you have a smaller tank that you could try out?

and remember a 14-16ft jon boat would be much easier to plane than a 10ft....

Sean
 
J

jetportdock

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Re: 15 hp mercury mouse hard to plain out

I also put a WHALE TAIL on it and made a big difference to plain out but cut the top speed around 1 to 2 mph but may be worth it.
 
Bondo

Bondo

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Re: 15 hp mercury mouse hard to plain out

Ayuh,... If it runs Ok with a full fuel tank, 'n Don't when it's low,...

I'd be lookin' at the fuel delivery system....
 
ONERCBOATER

ONERCBOATER

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Re: 15 hp mercury mouse hard to plain out

I must ask, did it run right before, is this a recent happening, or something that has happened since you got boat?
 
J

jetportdock

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Re: 15 hp mercury mouse hard to plain out

I just got the boat and the first time I have run it. I did get the carbs cleaned
 
S

steelespike

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Re: 15 hp mercury mouse hard to plain out

I would say the boat has a stern weight bias.Compounded by a relatively small planing area.
Its perfectly normal for that setup to have planing problems.Little vintage race boats similar setups would require the pilot to lean forward as much as possible to get planed out.Those with surface drive set up would seem like they would never plane.Once planed would run 40 or 50 mph.
The foil is a poor choice to solve the problem. Something like smart tabs carefully adjusted
Will help you plane with little or no speed reduction.
Motor height can also affect planing and top speed.Usually the anti vent plate(just above the prop)should be even with or slightly above the bottom.If the motor is really low raising could gain a couple of mph.You also need a tach before making any prop changes.A tiny tach is about $50 and easy to install.
If the boat is setup right for the most speed it is likely to be a little difficult to plane.
 
J

jetportdock

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Feb 6, 2011
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Re: 15 hp mercury mouse hard to plain out

Just wondering why a hydro foil not work good? Slower Top speed? I order my Tiny Tach so I will post some numbers on RMP's. I do not think I am going to mess with the prop because If I do get a smaller pich then my top speed would decrease right? I am looking at some smart tabs.. I assume this will not hurt the top speed. right?
 
S

steelespike

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Re: 15 hp mercury mouse hard to plain out

Unless the motor is setup very high you will be draging at least part of the foil through the water
The tach will tell you if you need a prop change.You should check the motor height;raising it could slightly improve hole shot and top speed. Smart tabs carefully setup will improve hole shot
with a minumum loss of speed. Too much pressure will cause the boat to flatten out and lose speed.If you contact smart tabs with your information they can help you make a selection.
Have you tried trimming in a notch?
 
C

captkevin

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Jun 15, 2009
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Re: 15 hp mercury mouse hard to plain out

What about adding a pair of smart tabs? Should give you a boost to getting on plane
 
S

steelespike

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Re: 15 hp mercury mouse hard to plain out

Can't tell anything from the pic.It needs to be at fin level.3" below is way off and kind of works like a lever pushing the bow up.The best solution is probably a jack plate. It will allow a fine adjustment. The motor could be 4" from where it belongs.The jack plate setback will allow even more height. Have you tried trimming in a notch? It will surely help but may cause the boat to lay down too flat.
 
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