Should I pull heads for inspection, 5.7 liter

[wryork25]

Ok so here is the story, motor runs rough, keeps fouling plugs. Wet and greasy looking. Rebuilt carb cause it needed it, dumping fuel at idle. Runs better now with clean plugs but will quickly foul plugs and then runs very poorly. I did a compression check on it and all cylinders are at 140 +/- less than 5. I did not do a leak down test because I don't have one. My block was replaced a few years back but I did not have the heads worked. I have owned the boat since 2008, should I pull the heads and inspect? Any ideas why I am fouling plugs so rapidly? Maybe the Valve oil seals? It is just crazy because it is all 8 doing it.

I have never pulled heads before but I am mechanically capable. I am a little hesitant I will be in over my head but I cant really afford to pay someone else to do it. Looked of Felt pro for marine gasket set but does anyone have suggestions on hardware replacement? Any tips or threads on the job?

 

[Bondo]

I did a compression check on it and all cylinders are at 140 +/- less than 5. I did not do a leak down test because I don't have one.

Ayuh,...... Welcome Aboard,...... My compression tester, the gauge is quick coupled to the hose that screws into the spark plug hole, so I remove the gauge, 'n hook up compressed air to it,....
By rotating each cylinder to it's Tdc, you can hear whether the rings, or one of the valves is leaking,.....

You need to figure out whether yer getting gas fouling, or oil fouling,....
You might still have a carb problem,.....
Or, by doing the test above, you might find the cylinders are glazed, or the rings never properly seated,.....
While it could be valve guide seals, that's abit of a stretch,....

Are you getting the fouling at idle, or when running across the pond,..??

 

[Scott06]

Agree with Bondo do some more investigative work before pulling it apart. You can do the poor mans leakdown like he mentions. Post some pics of the plugs and do you see fuel dripping of the venturis at idle?

 

[cyclops222]

Gasoline usually is a wet sparkplug at first. Oily / grease covered is a oil leak into the engine. All plugs ? Or random plugs are worse ? One cylinder head is worse than the other ?
You were sold a BAD batch of gasoline ? Did problem start after last time you filled up ? Rare but it happens.

 

[tank1949]

If saltwater boat and not antifreeze cooled, replace engine. My guess is rings are weak. Maybe valve seals are leaking oil into chamber?

 

[cyclops222]

Replace a engine ? Why, what destroyed it ?

 

[Mc Tool]

The fact that new plugs helped a bit may be a clue to weak ignition .
Check coil power supply whilst running . When did you last replace plug leads and can you test them ?
I had similar issue ..... blamed the carb ( to be fair .... I had been fiddling ) , but when I replaced the coil it was way better ..... for a day, then it was back to as before . Then I got the digital meter on the plug leads to check resistance and whilst not totally sure what resistance they should be I figured they should be all the same ...... they wern't , wildly different . New set of leads, put the old coil back on , ran like a Swiss watch .

 

[tpenfield]

I'd try some Mercury Power Tune to see if that cleans things out. A water mists into the carb while running can also help.

Do the leak down test. Once you take the engine apart, much of the diagnostic ability goes away.

 

[cyclops222]

I have found worn out H V coil wire that goes between coil and the center of a distributor cap to wear out. Erratic running of the engine. Have the H V cables been changed ? plug and coil leads been replaced ? Ever ? Buy the premade ones that fit perfectly.

 

[wryork25]

Ayuh,...... Welcome Aboard,...... My compression tester, the gauge is quick coupled to the hose that screws into the spark plug hole, so I remove the gauge, 'n hook up compressed air to it,....
By rotating each cylinder to it's Tdc, you can hear whether the rings, or one of the valves is leaking,.....

You need to figure out whether yer getting gas fouling, or oil fouling,....
You might still have a carb problem,.....
Or, by doing the test above, you might find the cylinders are glazed, or the rings never properly seated,.....
While it could be valve guide seals, that's abit of a stretch,....

Are you getting the fouling at idle, or when running across the pond,..??

I know its been a while since I posted this but I was Busy with work tdy. I am getting gas fouling. they definitely smell of gas and are wet. I am going to try and do a leak down this weekend. with the hose from my compression tester. Do you have any suggestions of finding TDC on the other cylinders? The first set is easy because it is marked on the balancer. I know it is a quater of a turn but how do you know when it is exact?

 

[wryork25]

Agree with Bondo do some more investigative work before pulling it apart. You can do the poor mans leakdown like he mentions. Post some pics of the plugs and do you see fuel dripping of the venturis at idle?

After rebuild of the carb there is no longer fuel dumping in the venturis, I will post pics of the plugs this weekend. they are wet foulded with gas.

 

[Scott06]

After rebuild of the carb there is no longer fuel dumping in the venturis, I will post pics of the plugs this weekend. they are wet foulded with gas.

After the carb rebuild they are still wet with fuel? Would clean or replace to see what is going on now. if still fouling plugs then carb isn't properly working yet or is it oil fouling? Did you set the idle mix properly and is the choke opening fully

You can ruin the rings by washing the walls with excessive fuel as mentioned might be worth a leakdown test