'98 Yamaha 90 HP

[bluka43]

There are two parts to my post. Back in November I purchased a very clean boat and motor from a guy I knew. I've always found that the motor seemed to idle very rough, but runs great after idle. It actually sounds like it's running on 2 cylinders instead of three. He had recently replaced the water pump and for some reason had removed the thermostat.(I'm not really sure that a thermostat is required in South Lousiana waters)
Secondly, The last two times that I took the boat out, after about 3 or so minutes of running at 3/4 throttle, the motor suddenly quits pulling like its in neutral and goes to idle speed,(it is still running mind you) without touching the throttle. I pull the throttle back to neutral, slip it back into forward and everything is good. Anyone has any idea what's happening?

[Hamfisted]

I sent you some info to your email. Clean out the idle jets. Check your shift cable adjustments.


Mike

[Ken]

bluka,
I agree with Hamfisted - low speed (idle) jets are probably clogged up. I would try a shock treatment with SeaFoam or RingFree first.
If the shock treatment does not work, then remove the jets and squirt some Berryman's Chemtool into the orifices.
If that does not work, then time to remove carbs, teardown, clean, and do a carb kit install.
Also, I would re-install that thermostat. There are conditions when the upper cylinder water jacket will not fill completely with cooling water without the thermostat. When that happens, you get uneven cooling of the cylinder wall and that can lead to warped cylinder wall and broke rings.
Good luck [img]smile.gif[/img] ,
Ken K

[bluka43]

Thanks for the replies guys. I'll try it.

Ken