Performance upgrades for 25 hp Yamaha 4-sroke

[cates81]

I was wondering if anyone knew of any performance upgrades for a 25 hp Yamaha 4-stroke. I have it on a CraigCat, which is basically two plastic pontoons and a fiberglass deck. It can't take much more weight at all, but I was hoping that I could just make a few modifications to the outboard that is on it. If you know of any way to gain some more speed let me know. By the way I have already changed props, I have 15, 12, and 8 pitch props.

 

[jim dozier]

Re: Performance upgrades for 25 hp Yamaha 4-sroke

I believe your best bet is to make sure the engine is running right, your bottom is clean, your hull is trimmed properly, your engine is at the optimum height and trim, and your prop lets the engine work at max operating rpm.<br /><br />Even if you were to attempt engine modifications you would be hard pressed to extract a 15% increase in power. These modifications if possible would be expensive (more expensive than buying a bigger engine). At best you would end up with a 28.75 hp engine with a shorter lifespan. If you really need more power trade up to a bigger engine. There is some difference in actual weight between brands of engines.