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iTrader: (1)

I am going thru a slow process ... checked compression (168) have been told it could be an oil ring and not show up with compression test... bypassed the oil cooler ... there are no PCV valves ..but I didn't blow the hoses out ...will check that ...believe me.....I aint yankin that motor out unless I have too ......

Mark .... you ran compression yet ?

Wobble

Not yet, I had a bad week last week. Thursday.. transmission went out in wifes car, Friday Morning.. boat messed up, Friday pm threw my back out and spent the whole weekend in major pain. Thats why i'm not strting on boat till next week.

I will do a compression and leakdown test before tearing it apart. However I am not hopeful in my case.

One other thing that can cause heavy oil use and displaced dipstick is water getting in oil. When oil gets to 212F this water turns to steam and creates crankcase pressure and carries some oil out breathers. If this is the case, you have to find source of water..

offthefront

iTrader: (1)

you trying to cheer me up ? nothing would surpise me .. had both motors out in the last year ...Starboard twice !! ....

So if you holed a piston ....just that one hole gets new stuff or do you go with new bearings and rings ? I guess that could be a decision made after everything is laid out on the table .....

88Fount33

When mine let go, I had used the new design cast piston but was supposed to be "like" forged. Replaced pistons (forged this time), bearings, polished crank, cam, lifters, and cam bearings. Mine was pinging & knocking but did not hear it at 5500 rpm through hulls. You fuel system sounds big enough, you did replace the pickup in the tank? Mine was 3/8" in the tank but the anti-siphon hose fitting wouldn't flow squat. Installed fuel pressure switch and idiot light on dash, and when I replaced the tank fitting, the light only came on when the engine was not running (and key on).

Wobble

Pulled motor last night. Ran compression test. 180-182 PSI all cylinders except #2 which was zero. Pulled head and found this..
My engine guy says that no sign of detonation on other pistons..
So I am stuck with the bad gas theory. Will have to sleeve this cyl to make it right.

Definetly only buying shell super from now on. Time to pump 80+ gallons of gas out and start over.

Anyone have any other explanation for this??????

Wobble

Anybody have any theories on this other than bad gas?

Thanks

Gary Anderson

Just one piston? Sorry, cant see pics but I would suspect there would be detonation signs in other cylinders too. Any chance you dropped a valve or ingested a bolt?
Gary

Wobble

I have motor pulled apart now. No bearing damage anywhere, no sign of detonation on any other piston. There is some aluminum in the combustion chamber of # 1 (correction, that is # 2). All the valve train is good. These pistons were cereamic coated on top. The intake is a single plane merlin. On the dyno we had 8 EGT probes and saw temps within 25 degree of each other. Still suspect bad gas but found out that octane test costs $600. So I am passing on that. Motor needs 1 sleeve and one piston and new cam bearings on account of the sleeving process.

Possible theories so far 1/ bad gas which detonted that cylinder because of poor coating on that piston. 2/ that piston runs hotter because of marine headers 3/ checked carb and seems to flow ok, but maybe temp obstruction on 1 venturie. 4/ some kind of ignition crossfire on that cylinder.
May never know for sure. Repairs are about $1500, I will never put offbrand gas in my boat again. It will be Shell or Exxon super both of which are made within sight of where I boat. Also I will run tank empty or drain at end of boating season.

Wobble

Sutphen,

Sorry, I have slept since this happened (not well). Hole is in #2 all other pistons perfect. All indications + dual EGT probes indicated motor was fat. This detonation was one cylinder only, thats why we are stumped.

Had 180-182 psi in other 7 holes. Engine is 9.4-1 hence the need for super.

Wobble

Sutphen,

It is a gen 4 bowtie block. I beleive gasket is on correctly. Though as you can see part of the water passage between 2 & 4 is covered by the gasket. I'm told this is normal!