Yamaha erratic running

[John Christopher]

I have a 1996 200 h.p. Yamaha Saltwater Series. All repair places around here are booked solid next 3 weeks. Engine runs perfectly at under 2000 rpm and over 4000 (neutral or under load makes no difference). Fuel and filters are clean. Between 2000 & 4000 the engine will lose rpm and then speed up all by itself - back and forth. Anyone have a suggestion? I am by no means a mechanic but quite useful with tools. Thanks.

 

[Silvertip]

Re: Yamaha erratic running

Sounds like a fuel delivery problem. Fuel pump is suspect. Make sure vent on fuel tank is open.

 

[ChasinTail]

Re: Yamaha erratic running

I have the same motor same year!!! This past weekend I had the boat out, it ran perfect!! Then coming in on monday, I noticed that I wasn't able to get Full throttle, and my rpms were jumping up and down. I decided to do some maintence that I was planning to do anyway (gear oil, spark plugs, fuel filter) I took the boat out today and noticed a big difference in response, however the rpm problem did not go away. I was able to at one point get the rpms to 5500 full throttle. Now I am only topping off at 5000, and every 5 secs the rpms would bolt to 5200, then back down to 5,000 and so on and so on.. Anything above 4,000 rpm it would do the same.

 

[ChasinTail]

Re: Yamaha erratic running

 

[ChasinTail]

Re: Yamaha erratic running

I spoke to a few people and they all pointed to the same thing.. Fuel problem. This is what I was told to do by an experienced Tech. Start with the fuel filter, then go to the water/fuel seperator, than the fuel pump rebuilds, than carb rebuilds. I am gonna try the seperator next, see what happens..