yamaha 300 hpdi runs rough

[WRECK]

Engine has 450 hrs, runs rough , compression 100, what can we check? Can ethanol damage these engines, Thanks

 

[Paison]

Re: yamaha 300 hpdi runs rough

Check plugs first. I have a Pair of 300's and go through quite a few plugs. Do you have a 10 micron water fuel separator installed. If not you would be saving yourself money in filter costs. Especially the metal $70.00 filter on top of the engine. Have you had the oil pump replaced ie. Yamaha recall? Check compression in # 2 cylinder. Or all of them while you have the plugs out. Try these things and maybe you can come up with an answer.
Regards. Charlie C.

 

[yamamarinetech40]

Re: yamaha 300 hpdi runs rough

WRECK, when you say runs rough...idle, high speed, or always? Start suddenly? How much ethenol? You could get a glass or clear container and shoot a sample(pint at least) with the primer bulb into it...see what comes out(you know what FRESH gas smells like). Could be so many things, from so little info....

 

[WRECK]

Re: yamaha 300 hpdi runs rough

I 'm trying to get some info; the boat is now on land, owners tell me it runs rough, as is sale. Open to all options? what should be compression 2004
motor, 250 -300 hpdi 2003 -2004 same? Thanks for the help.

 

[rodbolt]

Re: yamaha 300 hpdi runs rough

compression should be within 10 PSI on all cylinders.
look at the oil pump control arm, it should be a 60VD4 I believe,
if not there is an update.
runs rough can be a host of thigs from cheap to very expensive.