1996 5.7 Mercruiser - no compression

[Danmunoz77]

Had spark, fuel, crank but no start on starboard motor.


Did compression check. No compression in cylinder 8. 60 psi on cylinder 2 and 80 psi on cylinder 5. All the rest 150+/-5. Boat has 520 hours. 310 celebrity sport cruiser.

Valves? (Took covers off and all push rods are moving )

Rings?

THANKS.

 

[Scott Danforth]

welcome aboard

my guess salt water

my guess your manifolds failed

my guess, the valves are rusted, and possibly the bores too.

at a minimum, do a leak down test.

 

[alldodge]

I would at minimum pull both heads, but if it was mine, just pull the motor and rebuild

 

[tpenfield]

Hydro-lock maybe. bent some connecting rods :noidea:

 

[tank1949]

Had spark, fuel, crank but no start on starboard motor.


Did compression check. No compression in cylinder 8. 60 psi on cylinder 2 and 80 psi on cylinder 5. All the rest 150+/-5. Boat has 520 hours. 310 celebrity sport cruiser.

Valves? (Took covers off and all push rods are moving )

Rings?

THANKS.

If salt water cooled (open) then get another motor. Almost 20 years in a salt bath aint good on iron. I would not rebuild a salt water cooled old block. First, make damn sure that your compression tester is working 100%. I had one that had a loose bleed off valve. Cylinder pressure was leaking through it. I tried another tester and read good pressure. I then notice bad valve.

 

[Bondo]

Had spark, fuel, crank but no start on starboard motor.


Did compression check. No compression in cylinder 8. 60 psi on cylinder 2 and 80 psi on cylinder 5. All the rest 150+/-5. Boat has 520 hours. 310 celebrity sport cruiser.

Valves? (Took covers off and all push rods are moving )

Rings?

THANKS.

Ayuh,...... Welcome Aboard,....... So what's the back-story,..??

New to you boat, with no history,..??
Runnin' across the pond, 'n it died,..??

Do a leak-down test to see where the compression is excapin' the cylinders,.......

 

[Lou C]

When you did the comp test...did any water come out of the plug holes? Were the electrodes on the plugs rusted? Did the center electrode have an orange rust colored cast to it? All those things are signs of water in cyls. That can be due to various causes but if none of that is true next do a leak down test to tell the tale. Most likely valves not seating but the one reading zero could be a totally stuck valve. Often valve problems are due to water ingestion due to faulty exhaust or in some cases a blown head gasket can let water in as the engine cools off, it does not always show as low compression between 2 adjacent cyls as most people think.