250 HPDI low compression! WHAT TO DO???

[perryk123]

Hi, got an 04 250 hpdi that had even compression across the board (110lbs) before i ran her for the first time this season. Got her in the water fired right up, but didnt want to idle. So took her back to shop and drained fuel, replaced the fuel filters, and fired her back up. Still no idle. Pulled plugs to see if they were foul and the were kinda black except for the two lower plugs on both sides that looked as if they were not as oily (kinda light brown). While i had them out figured what the hell pull a comp test. All were at 110lbs except port center cylinder had 70lbs. Im guessing thats why she doesnt wanna idle. is there anything anyone can recommend?

the boat was sitting for some time (months), what measure should i take.

Anyway to bring that compression up other than rebuild

Thanks

 

[robert graham]

Re: 250 HPDI low compression! WHAT TO DO???

You could run a couple of tanks of gas treated with Ringfree at the "deposit removal" dosage of 2 ounces per gallon of gas, hopefully will remove carbon from rings, in ring grooves, ports, etc., then re-check compression on each cylinder. Good Luck!

 

[rodbolt]

Re: 250 HPDI low compression! WHAT TO DO???

DO NOT run that engine anymore.
it may or may not be rebuildable now anyway.
its time for a teardown.
remove that head and the intake and reed cage assy to inspect for the extent of the damage.
usually its detonation from either low high pressure on the HP rail or a partially clogged injector screen or simply bad fuel.
keep running it and it will toss a rod through the block.

 

[perryk123]

Re: 250 HPDI low compression! WHAT TO DO???

thanks Rodbolt your a big help. think i might take her to someone that knows what they r doing. Unfortunately there is no such thing as a YAMAHA tech in Arkansas, but maybe I'll get lucky.

 

[rodbolt]

Re: 250 HPDI low compression! WHAT TO DO???

use the Yamaha dealer locator search function.
try to use a dealership with at least 1 master tech employed.
that power head takes about 1 hour to pull then you can ship it anywhere in the US.

 

[perryk123]

Re: 250 HPDI low compression! WHAT TO DO???

Rodbolt,

the only mastertech in the area, worked on a boat for me last year and spent $2200 of unnecessary parts without fixing the problem, and then turned and told me just to sell the boat, cuz it would always have problems.

After 3 months I spoke with you through the forums and ordered a new oil tank and installed it myself (AND IM NO MECHANIC) and the problem was fixed.

Does the whole block need to be bored out. what would you recommend i have done? or what should i make sure they do?

thanx