Yamaha 225 2-stroke power problem

mcm114

Cadet
Joined
Jul 4, 2007
Messages
18
I recently bought a ski boat with a '91 225hp TLRP engine. I only use it for a couple hours at a time in the morning or late afternoon. For a while I was putting 87 octane in the tank, until I started getting power fluctuations at all rpm ranges. When that started happening, I drained the tank, got a new water seperator/filter, and started using 89 octane only. From there I didn't have a problem for over a month. Last weekend, after a long morning of skiing, we were headed back to the dock and the rpms started lapsing, the same way it did before. The person driving at the time (not me) yanked the throttle back very quickly, and it immediately died. I couldn't get it started this time (before I was always able to nurse it back.) At the dock, I swapped out all the plugs, which all seemed to have a lot of fouling. No gaps bridged, but just a lot of carbon and oil. I also disconnected and reconnected the two wiring harnesses going into the computer. After all that, (or maybe the long rest) it finally cranked. There was a lot of oil coming out of the exhaust as well as what looked like carbon fouling floating on the surface (little chunks of black crusty stuff). I figured I had flooded the engine while turning it over so many times trying to get it started. It was idling very rough at this point, but I was able to drive it on the trailer. As I was doing this, the engine quit a couple more times, and when I turned the key the warning horn made a single beep (which it never did before). It had been sitting long enough for me to change all the plugs, so it should have been relatively cool. Water coming out of the tell-tale and everything. But now I wonder if it just overheated from pulling skiers all morning.

I don't have a service manual yet, but I've been doing some blind troubleshooting. The fuel system seems intact, that is if I pump the primer bulb (engine not running), there doesn't appear to be a leak, and there is fuel going to all the carburetors. I'm taking it back to the lake tomorrow, with a new tank of gas. Anybody have any troubleshooting tips for me?
 

Ray Neudecker

Lieutenant Commander
Joined
May 25, 2004
Messages
1,656
Re: Yamaha 225 2-stroke power problem

Not postive on that year but the previous models required premium fuel. Do a compression test first.
 

mcm114

Cadet
Joined
Jul 4, 2007
Messages
18
Re: Yamaha 225 2-stroke power problem

I will do the compression check, but as long as we're talking...what range should I be looking for?

And on a side note, I know that higher compression ratios require higher grade fuel, but exactly what compression ratio would require the use of premium gas?
 
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