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Author Topic:   Yamaha 70 Cuts Out at High Speed

Quogue posted 09-09-2007 08:27 PM ET (US)
Hi all. I have been having a recurrent problem with my 1986 Yamaha 70-HP (that I have on my 15 Whaler). After a couple of miles at top end, the engine cuts out. When I re-start, the engine usually runs only on one cylinder and I have to limp home. After a rest it runs like a champ until I tax it again. [Do readers have] any ideas [of the cause]? The water pump is not new, but it seems to stream well. I was told fuel [might be the cause]. I emptied and changed the gasoline, and added a fuel separator with high hopes, but same problems. Otherwise the engine runs great.
Tom Hemphill posted 09-10-2007 07:06 AM ET (US)
My 35-horsepower Mercury outboard of the same age had similar symptoms. Since the carburetor was just rebuilt and other fuel delivery components replaced, my mechanic judged it to be an ignition problem. He replaced the ignition coils and trigger assembly and the problem hasn't reoccurred.
jimh posted 09-10-2007 08:51 AM ET (US)
Sounds like a heat related problem. Some electronics do not like to perform when they get hot.
Quogue posted 09-10-2007 08:45 PM ET (US)
Thanks! I will head in that direction. Hopefully have this fixed by next season.
Quogue posted 10-03-2014 08:29 AM ET (US)
[Seven years later...] A very late follow up: [the cause of the Yamaha 70 outboard engine cutting out after a couple of miles at top end] was water in the [fuel] tank. Once the tank was removed and fully drained, all was good.
jimh posted 10-05-2014 04:03 PM ET (US)
[Moved to REPAIRS/MODS. The initial posting to another forum tended to direct the discussion of a remedy toward electrical problems. As we found out, seven years later, the problem was not at all related to the boat electrical system or any electrical or electronic component.--jimh]
Tom Hemphill posted 10-05-2014 06:33 PM ET (US)
Thank you for the follow-up, Quogue.

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Author	Topic: Yamaha 70 Cuts Out at High Speed
Quogue	posted 09-09-2007 08:27 PM ET (US) Hi all. I have been having a recurrent problem with my 1986 Yamaha 70-HP (that I have on my 15 Whaler). After a couple of miles at top end, the engine cuts out. When I re-start, the engine usually runs only on one cylinder and I have to limp home. After a rest it runs like a champ until I tax it again. [Do readers have] any ideas [of the cause]? The water pump is not new, but it seems to stream well. I was told fuel [might be the cause]. I emptied and changed the gasoline, and added a fuel separator with high hopes, but same problems. Otherwise the engine runs great.
Tom Hemphill	posted 09-10-2007 07:06 AM ET (US) My 35-horsepower Mercury outboard of the same age had similar symptoms. Since the carburetor was just rebuilt and other fuel delivery components replaced, my mechanic judged it to be an ignition problem. He replaced the ignition coils and trigger assembly and the problem hasn't reoccurred.
jimh	posted 09-10-2007 08:51 AM ET (US) Sounds like a heat related problem. Some electronics do not like to perform when they get hot.
Quogue	posted 09-10-2007 08:45 PM ET (US) Thanks! I will head in that direction. Hopefully have this fixed by next season.
Quogue	posted 10-03-2014 08:29 AM ET (US) [Seven years later...] A very late follow up: [the cause of the Yamaha 70 outboard engine cutting out after a couple of miles at top end] was water in the [fuel] tank. Once the tank was removed and fully drained, all was good.
jimh	posted 10-05-2014 04:03 PM ET (US) [Moved to REPAIRS/MODS. The initial posting to another forum tended to direct the discussion of a remedy toward electrical problems. As we found out, seven years later, the problem was not at all related to the boat electrical system or any electrical or electronic component.--jimh]
Tom Hemphill	posted 10-05-2014 06:33 PM ET (US) Thank you for the follow-up, Quogue.