3.0 4cyl merc problems

[Speedylifsavr]

My first boat!

Had it for a month and hasnt been in the water yet!

Long story short , after having the boat for 2 days I started it up with muffs on and it stalled . Checked things over found water in engine . flushed engine , changed oil and located root of problem - cracked manifold .

I replaced manifold and riser , put her all back together and no start . I noticed on the compression stroke on #3 cylider air and fuel being forced back through intake?

started digging around found distributor to be off and firing order wrong . (god knows who worked on this boat before , kinda scary)

After fixing that problem I manage to get it started , runs great for a few min . I shut it off and try to restart - no go .

pulled plugs , #3 has fuel all over it?

Any ideas what could be causing this? compression good in all cylinders , have not done a leakdown test yet as my guage broke on tester .

Also how do you time this thing , there is a small timing scale by the crank pulley but I dont see any corresponding marks on pulley itself?

 

[jedimaster]

Re: 3.0 4cyl merc problems

There should be a little notch in the pulley. Mine was a bit corroded and was very hard to see. once I found mine I sanded it off a bit and put a dab of white paint on it.

 

[cheburashka]

Re: 3.0 4cyl merc problems

These engines are pretty simple. If one cylinder has excess gas, about the only thing it could be is a spark problem. Are you sure that plug wire and plug are both good? Did you replace the distributor cap? Might be time to just do the rotor, cap, wires and plugs just to rule those out.

I guess it could be something in the valves on that cylinder as well, although if you have good compression, there's very little chance of that. You said compression was good. What are the numbers?

 

[Speedylifsavr]

Re: 3.0 4cyl merc problems

compression

1 148
2 138
3 135
4 136

was also leaning towards valvetrain issue , maybe intake valve not seating correctly allowing excess fuel into cylinder .

 

[cheburashka]

Re: 3.0 4cyl merc problems

compression

1 148
2 138
3 135
4 136

was also leaning towards valvetrain issue , maybe intake valve not seating correctly allowing excess fuel into cylinder .

Very unlikely. If it's on the firing stroke, the valve is open through the whole down stroke. If the valve was open enough to let fuel in on the exhaust down stroke, you wouldn't be reading 135. Have you checked the spark on 3? Are you sure it's firing at speed?