how can i add a few more hp to my outboard motor?

Question

I have a 15 hp outboard motor on my boat, its way too slow as is, let alone having 5 people on board. As i don't have money at the moment to get a bigger one, is there anyway i can add a few more hp cheaply and without destroying my engine?

Answer 1

You could start simply by replacing the spark plug(s) and seeing if that helps... or maybe trying the "splitfire" plugs... they claim to increase HP... The other thing I might try is to make sure that the fuel filter is clean... (the faster you try to go, the more fuel required) while it wont "increase" HP - it will make sure your fuel flow is unrestricted so that you can acheive maximum HP.

The other thing that you could try is different pitch propellers... Pitch and diameter on a prop work this way - the first # is diameter of the prop and the second number is how many inches of thrust is generated by 1 revolution of the prop screw. So going lower in pitch will give you more RPM's as it has less thrust - but this typically equals a better hole shot as the prop can rotate faster to get up to optimal RPM quicker. Conversely - if you want more high end - you can increase pitch - the boat may not get on plane as well - (which sounds like your possible problem translating to a lack of hp) - will have a higher inch per revolution but total lower RPM at wide open throttle.

If you start fiddling around with this - I'd try a lower pitched prop first... but watch the RPM's so you don't blow your motor.

I feel like I'm about to state the obvious, but here goes... depending on the type of boat - 15 hp may not be enough to push the boat, motor and 800lbs of people. My boat has some performance loss when I have 5 people aboard and it's 19' with a 4-stroke 140hp.

Answer 2

assumimg you have a two stroke engine and your maintenance is good, your prop will change the performance of your outboard, but i don't think that's what you are looking for. If you are in your boat with two people i'm assuming the boat is propped right because that doesn't seem to be your complaint. 5 people in the boat doesn't give you the power you're looking for. Well you can do this and it will increase your power. Take the power head off, then pull the mounting plate off that connects your exhaust jug to your lower unit. When you pull this your exhaust manifold is mounted to the plate. Pull the manifold off of the plate and measure 1 inch up and cut the manifold. one side should be longer than the other so be careful that it remains that way when you cut it. After you do that then remove the jug and seals in the center section. Go buy new exhuast manifold gasket and power head mounting gaskets and put back together. OH, by the way you will have to drill two 1/2 inch holes in the rear of the center section to allow your newly tuned engine to breath. You will be impressed with the difference in the sound and performance. Good luck. P.S. Don't let anyone tell you an engine is to small to get some ponies out of. If it runs, it can be done.

Answer 3

If it is a 4stroke there is very little you can do except increase the cc. with a 4stroke you can change exhaust etc but they only give a very small increase in power. 5% at best to increase a 4strokes hp you need to increase the cc 150 >188 etc. if it is a 2stroke then the oppisite applies. a good exhaust can improve power by 20% and you still have the option of increasing the cc. hope this helps.

Answer 4

Buy 6 bottles of tomato sauce(hp sauce) and pour it into the engine hopefully that will do the trick. And give the rest of us some peace away from noisy water borne boats.

Answer 5

Lower the Prop pitch will give you more Rpm morepower but don't except much it's only 15 HP.Less people??

Answer 6

forget it. too small. if you had a 150 or bigger there are some kits on the market that can boost hp quite a bit.

Answer 7

try super fuel with an octane booster.

Answer 8

shave the head. run 94