650 Waverunner Question

[tnfreebird]

Okay, just for clarification I have a Boston Whaler Rage 14 which is powered by the 650 Yamaha Waverunner propulsion system. The Yamaha folks go brain dead when I talk to them about a Boston Whaler, and the Boston Whaler folks do the same when I talk about engines period.

The engine will not rev past a fairly low rpm range. I first thought it might be the rev limiter which is activated by an overheat sensor. Turns out that is not the problem. Changed plugs and fuel filter and recently had a compression check done. I hate to admit it, but I don't remember what the compression numbers were, but one cylinder was a good bit lower than the other, but nothing huge.

The engine will rev to speed only when I can cavitate the pump. Other than that, it just runs nice and smooth, right up until it hits that brick wall. Any thoughts or ideas?

 

[tsinnaples]

Re: 650 Waverunner Question

What Were The Numbers On The Compression Check?
What Do The Plugs Look Like After You Run The Engine At The Speed It Wont Go Over For A While?
Hows Does It Idle?
Doed It Run Smooth Or Rough At The Max Rpm It Will Go?

 

[tnfreebird]

Re: 650 Waverunner Question

sorry, double post.

 

[tnfreebird]

Re: 650 Waverunner Question

What Were The Numbers On The Compression Check?
What Do The Plugs Look Like After You Run The Engine At The Speed It Wont Go Over For A While?
Hows Does It Idle?
Doed It Run Smooth Or Rough At The Max Rpm It Will Go?

As stated, I don't remember the numbers on the compression check, but the person who did the check said it should not account for the lack of rpm. I can retrieve them and post them later.

Frankly, I have never run the boat for an extended period of time followed by checking the plugs. I did an initial check for general condition, and both appeared the same. This after about an hour of running when I bought the boat.

The previous owner stated the low rpm thing previously took care of itself after running a while, but during the sea trial it never overcame the problem. According to him, this problem had developed during the last two times he ran the boat. I made an offer based on the uncertainties, and he accepted.

The engine idles fine.

Again, it just runs nice and smooth, but it will not reach rated rpm. I did have a Yamaha tech in FL tell me it sounded like a stuck choke as he had seen that before with these symptoms. I checked, and the choke is open, unless of course there is another choking device that I'm not seeing. Kinda doubt that.

Thanks for your reply. Maybe the additonal info can help you help me.

 

[Jeff Walkowiak]

Re: 650 Waverunner Question

probably needs the carb rebuilt starving for fuel, try a shot of start fluid in the air box when it starts to loose power and see if it jumps up if it does it needs more fuel and the carb is clogged or the diaphragm is bad