1989 Yamaha 225 Intermitent Problem

[JohnBNTampa]

While the motor is running at about 4000 RPM it will drop to 3500 RPM by itself. Sometimes it sounds as if it is "surging." I am not touching the throttle at all when this happens. Acts as though I were gunning it and then letting off. It doesn't happen all the time. Any suggestions on the possible problem? The motor doesn't sound like it is missing.... Have heard a muffled backfire or two the past two times I took it out when cranking it. Possible fouled plug? Thanks in advance for your response. :O)

 

[t_bird]

Re: 1989 Yamaha 225 Intermitent Problem

my brother had the same engine w/similar problems, after months of trial and error, he found a little piece of rubber,I mean real little,in his fuel pump..

 

[rbu]

Re: 1989 Yamaha 225 Intermitent Problem

I have a 1988 V6 Excel. Mine did that but at a lower rpm. It was the rev limiter kicking in due to overheating. Although, that doesn't sound like your problem since the limiter brings it down to around 2500 and you are around 3500.<br /><br />It sounds like what t-bird is saying. The engine is starving for fuel. What you can try when it does this is to have someone manually start squeezing the priming bulb and see if it stops. Then you'll know that if it is a fuel starvation problem and go from there.<br /><br />Also, have you ever replaced your fuel pumps? Late 1980's Yamaha fuel pumps did not use stainless screws inside and they will eventually start to rust which will contaminate your carbs. I replaced mine last year and sure enough, they were rusting and there were small bits of metal inside the pumps. It's an easy fix. Just get 2 new pumps and bolt them up there. Don't bother with the rebuild.

 

[MIKENVAHBEACH]

Re: 1989 Yamaha 225 Intermitent Problem

I have this very same problem. What ever happened?

 

[arctic cruiser]

Re: 1989 Yamaha 225 Intermitent Problem

I have recently aquired a 21 ft boston whaler with a Yamaha V6EXCELLG, serial # 6K7 L 300928.<br />Checking the motor up and down has not revealed year and hp. Have asked several other web sources and get different answers every time. Can anyone help me out.....