'96 Yamaha 25HP - Lacks Thrust

[cbell2152]

'96 Yamaha 25HP - Manual Start, Tiller Steer - C25MSHU

Engine has no problem starting, 'pees' water, and runs well at low RPMs. However at 50% throttle and above, I'm not getting the normal amount of thrust/power even though the engine sounds normal at the higher RPMs. I'm getting much more smoke/steam than normal, a much bigger wake behind the boat, and eventually steam spurts out of the 'pee hole' if I continue trying to run it at higher RPMs. This problem started around the same time I moved into a home on a lake canal and began keeping the boat in water (Since its been kept in water, I've run the engine everyday).

The obvious answer to my problem is that my intake/exhaust system is clogged due to keeping it in a not so clean water canal. But I guess I'm not understanding how that could true be if the engine is peeing water just fine at low and high RPMs... I've tried flushing it for 15 minutes everyday for the last week w/ the hose & rabbit ears but get the same result when I get out on the water and try to give it full throttle.


Any tips, insight, suggestions, etc. would be greatly appreciated...

 

[BaileysBoat]

What is the motor hanging off of? Big wake or big rooster tail? Seems like a like a trim issue. Trimmed too high and sucking air = overheat.

 

[cbell2152]

Motor is bracket mounted directly to the stern of the boat, no jack plate or anything fancy to lift it with. Big wake with no rooster tail... I've had others suggest I might have a trim issue, but it seems odd considering the trim hasn't been adjusted in the 4 years I've owned the boat and this problem has only come up in the last 2 weeks.

I'll try dropping the motor though and see if it makes a difference when I take her out this evening. Thanks BB