'02 Yamaha 200 problem - The Hull Truth

charlie2665 · 12-13-2007, 03:27 PM

Andy,

I'm encountering a problem with my '02 Yamaha 200 EFI (OX66 Saltwater SeriesII). It has me ready to pull out what little hair I have left!
A little background...this past summer the engine was running perfectly for about an hour of run time each trip. Then suddenly it would go into rpm reduction, and I'd limp back to the dock. It was not overheating or having an oil problem. There was no alarm going off or anything. I had one mechanic give up on it because, of course, the engine would run perfectly when he tested it. I would get the boat back, go fishing, and have the same problem over and over.
Finally, another mechanic ran test after test with no results. He finally found a small leak in one of the manual furel pumps under the cowling. The gasket had a very small leak. He replaced the pump, and the engine began running perfectly with no problems.
I'd say I got at least 6-10 trips in with absolutely no problems. Now here's the latest...the engines surges (stop and go action) when returning home from fishing in the ocean with a following sea. The ONLY time it surges is when I drop off a wave on my way IN from fishing. The engine purrs when I'm plowing into a headsea going out. Also, it purrs when I'm inside the inlet on flat water. It shows NO problem whatsoever the entire day until I pick up to head home. It literally does the stop and go thing 100% of the time dropping off a wave. The engine drops way down in rpm's then picks back up after coming off the wave. It doesn't have to be rough at all. These are not big waves! I usually cruise about 4100 to 4300 rpms. I can only put the engine at about 3600 to keep it from doing the stop and go thing. As soon as I come in the inlet and stop bouncing, the problem stops immediately! Like I said, it only happens when dropping off a wave with a following sea, NEVER going into a headsea.
Is there any suggestions I can give to my mechanic so he has a starting place, or am I going to have to suffer through countless tests with no results? Is it electrical, a fuel situation, etc?
Thanks so much for any guidance you can provide.
Frustrated in Florida...

Sea Ya!
Charlie

SIM · 12-13-2007, 06:36 PM

Well it could be anything Charlie. Without being to look at it personally, I would just be guessing.

But I will say.....If I was to go out and troubleshoot a Yamaha OX engine, there are some tools I would bring along that without.........it would just be a plain waste of my and my customers time.These are.........anOX66 diagnostic indicator tool,a fuel pressure gauge, TPS test harness with a DVM, timing lightand my fuel line vacuum gauges. I hookconnect them up and go and run the boat under load duplicating the running issueand go from there. Chances are that one of thosetest toolsis going to give me a clue as to what the problem may be.

You do not mention the VST.......was that dis-assembled and was the pump strainer checked or cleaned
eplaced? Does the engine maintain the proper fuel pressure under load?

Andy

John_Madison CT · 12-14-2007, 05:09 AM

I had the same thing happen to me with my last boat running an Ox66. It was a clogged VST filter.

charlie2665 · 12-17-2007, 05:34 PM

Thanks for the information, Andy. I will share this with my mechanic. Also, I will review every test that was run for the last repair. I'm sure we'll get to the bottom of it now!

Sea Ya!
Charlie

charlie2665 · 12-17-2007, 05:37 PM

Thanks a bunch for the response, John. I had someone else respond with your same answer. Hopefully, that will be the culprit and I can't get back to smooth running!

Sea Ya!
Charlie