Help with Yamaha Outboard

[dancer4life]

Hey guys,
I have a neighbor that has a 2017 Yamaha 250hp 4-stroke. I have been doing the basic maintenance on it for the past few years and it has alway ran great. This summer it started running pretty rough in the 5mph to 10mph range. It idles great and from 10mph up to full speed it runs great as it always has. But when he is in the No Wake zones, it runs pretty rough.
Any ideas? I replaced the gas filter about 5 months ago. Dirty fuel injectors, spark plugs?????

Any help would be appreciated.

 

[SoonerP226]

If it were a car or truck, I'd suggest the coil(s). Light- to mid-throttle misfires are classic signs of coils that are starting to fail in modern engines.

 

[birdhunter1980]

I would try cleaning the injectors or running sea foam through it. Could be a vacuum leak somewhere, cracked hose or something else maybe along the intake. I'm not a professional boat mechanic by any means but I've worked on a few of my smaller motors. Good luck!

 

[birdhunter1980]

If it were a car or truck, I'd suggest the coil(s). Light- to mid-throttle misfires are classic signs of coils that are starting to fail in modern engines.

This too!

 

[dancer4life]

I would try cleaning the injectors or running sea foam through it. Could be a vacuum leak somewhere, cracked hose or something else maybe along the intake. I'm not a professional boat mechanic by any means but I've worked on a few of my smaller motors. Good luck!

Thanks bird hunter, We thought about running sea foam through it as well. Planning on doing tha next weekend.

 

[Bocephus123]

suck the tank dry and start over id say 91 no ethanol but manual would say for sure.

 

[Snattlerake]

Thanks bird hunter, We thought about running sea foam through it as well. Planning on doing tha next weekend.

Spray carb cleaner around the hoses while it's idling. You will get a surge in RPMs when the cleaner gets sucked in a leak.

 

[montesa]

You should see what the plugs look like after idling.

 

[TinkerTanker]

I got a similar effect when my bulb had hairline cracks. You can't see them, but if he hasn't changed the bulb in over 5 years it's due.

 

[dancer4life]

I got a similar effect when my bulb had hairline cracks. You can't see them, but if he hasn't changed the bulb in over 5 years it's due.

I would have never thought of that. Thanks!!!!