total compression loss 470 merc

[starstuck1979]

I have a 1979 starcraft with a Merc 470 170 horse with a 470 leg been running strong for a year son took it out for a trip shut it down on the lake. the engine would not turn over turned out to be a failed starter relay replaced relay. tried to start engine turned over real easy I was not home at this point when I arrived home 25 days later I attempted to start it no go, pulled the plugs to do a compression test I now have 0lbs on all 4 cyls I did discover water in the intake and the plugs were wet with water when I pulled them.I put a 3/4 inch socket on the harmonic balancer to check rotor position for TDC there is a clicking sound coming from the engine as I turn it over by hand .This engine ran strong before this with the exception of bogging issues ordered a carb kit from Mikes does this sound like a catastrophic failure no notable sounds like valves hitting pistons valves all see to be moving the same range of travel any ideas would be really appreciated at this point as I am at a loss without to tear this totally down

 

[Scott Danforth]

Welcome aboard.

you probably lost the head gasket. if so, buy a mercruiser gasket, the aftermarket head gaskets do not work.

 

[stonyloam]

were the plugs wet with water or coolant?

 

[wahlejim]

The only catastrophic failure is a cracked block. All other gaskets, etc. can be replaced. Either way, it sounds like that engine needs to come out and gone over.

 

[starstuck1979]

The plugs were wet from water just pulled the head gasket is good no antifreeze came out of the manifold the head looks fine timing chain looks near new,I'm nearly bald ,scratching my head how is it possible to get no compression at all 0lbs how can you do a visual check for a cracked block the sleeves look fine .would a cracked block cause a loss on all four cyls

 

[starstuck1979]

Thanks for your feedback this is my first boat 18ft aluminum starcraft got 1 1/2 summers of trouble free fun not bad for a 36 year old boat looking like a resto looking forward to it will be back looking for more info in the future

 

[Alumarine]

Are you sure the compression gauge is working properly?

 

[starstuck1979]

yes I also stuck my finger in the plug hole while my wife turned the engine over

 

[nola mike]

Did you overheat? These HG fail because you have an iron head on an open deck aluminum block, and there's a lot more shift possible between the head and block than on most engines. I'm guessing it's possible to have that movement without actually having an obvious HG tear or whatever, though others can chime in on this. Anything going on in the block wouldn't be subtle. I'm assuming that you checked to make sure the valves are closing? Possible that water in the cylinders rusted some valves in place.

 

[stonyloam]

Yeah I'm with mike on this. 0 compression says stuck valves.