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  1. #1

    Default "My port engine was idling rou

    "My port engine was idling rough so I ran a compression test, engine is about 20 hours new so I was suprised to find zero compression in one of the cylinders. I dumped oil in the bad cylinder with no compression change. All of the other cylinders had over 120lbs of compression. What to do now? Would I be better off installing new heads or having a head job done. Or should I just put in a new long block? I'm not sure where to even purchase one in Southern California. The boat is not trailerable."

  2. #2
    Join Date
    Mar 2009
    Lowell, MA

    Default "Take of the valve cover, turn

    "Take of the valve cover, turn the engine over (but dont start) while watching the valves rockers, could be a stuck valve. ( hope it didn't damage the piston)

    Southern Cali is like the boating capital of the US isn't it ? Should be able to find an engine or get one there.

    If you have a stuck valve, pull the head and have the guide replaced and get a new valve.

    So was any head work done to the heads ? Should definately find out."

  3. #3

    Default "Pulled valve cover, valves ar

    "Pulled valve cover, valves aren't stuck. Could it be a blown headgasket? Longblock is nearly new."

  4. #4
    Join Date
    Sep 2008
    Maryland - USA

    Default "what did the spark plugs look

    "what did the spark plugs look like?

    If white and glazed, could have a hole in the piston from running too lean.

    If tan or darker, could be the head gasket or other head related issue.

    A leak-down test would help pinpoint the problem"

  5. #5
    Join Date
    Sep 2003
    New Tripoli, PA, USA!

    Default "I hate to say it, but there m

    "I hate to say it, but there might be a hole in a piston. Hope I'm wrong. Either way, the head has to come off.


  6. #6
    kingfishy's Avatar
    kingfishy Guest

    Default "Jeff, My experience with C


    My experience with Chrysler's tells me it's a bad gasket you're most likely dealing with. I have yet to see one with a hole in the piston,but it can happen ..i'm sure.

    I would fill the cylinder with oil and see if it drains down or stays at the plug hole. Course, at some point you'll need to yank the head regardless,so i spose thats yer call...but i would want to know before i started ripping things apart.

    Zero is mighty low, i would think Nominal would be 150 LBS per cyl.

    Let us know what you find when you yank the head.


  7. #7

    Default "I pulled the heads and found

    "I pulled the heads and found that a valve seat had somehow come loose from the head and wedged itself under a valve preventing the valve from closing. This explains the zero compression reading. I also discovered water in the aft cylinders on both sides of the engine. I know I need to replace or rebuild the heads, my question is where is the most likely place to look for the water leak in the engine? The head gaskets look fine."

  8. #8
    Join Date
    Sep 2003
    New Tripoli, PA, USA!

    Default "Exhaust manifolds and/ or elb

    "Exhaust manifolds and/ or elbows/ risers. You can pressure test each piece (off the motor) to see where the water is coming in but, considering you have water on both sides, I'd suspect the whole works needs replacement.

    Glad to hear there wasn't a hole in the piston. Ran into several of them lately.


    PS: Those heads don't normally have removable seats. I suspect someone (poorly) repaired that one. You might consider finding another one."

  9. #9

    Default "Thanks Jeff, you are correct.

    "Thanks Jeff, you are correct. Apparently Chrysler marine engines shouldn't have valve seats. I've been told that I'm lucky only one valve seat failed and that the seat didn't cause more serious engine damage. Anybody know where to buy affordable 318 marine heads?"

  10. #10
    Join Date
    Sep 2003
    New Tripoli, PA, USA!

    Default "TGry this guy (Craig Powe

    "TGry this guy (Craig Powell):

    [email protected]

    Say I sent you.


  11. #11
    Join Date
    Sep 2008
    New York, NY, USA

    Default "Brexon, I actually have 2

    I actually have 2 heads from a 360 if that will work. I bought them just last year for my 360 and then i ended up replacing the whole motor (cam problems). The new motor came with heads so I now have 2 heads with about 6 hours on them. If you're interested, let me know.

    Dan [email protected]"

  12. #12

    Default "Thanks Dan, but I purchased s

    "Thanks Dan, but I purchased some automotive heads online. Now I just need to replace the freeze plugs. I do need a good source for manifolds and risers if anyone has any ideas."

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