60 HP 3 cylinder low compression

[stivov1]

have a 1993 60hp, all 3 cylinders are about 75psi, are these motors low compression motors or is it time for rebuild? will they run with that low compression?

[rock]

If all cylinders are the same I might question the gauge.

Rock

[sharpeye Mike]

Has it been sitting for a while? Cylinders might be dry

[stivov1]

I've been using this guage rock with all my motors, so it should be good. yes it was sitting for a while, I lubed up the cylinders prior to testing

[sharpeye Mike]

I picked up a OMC Stinger for parts one year that was sitting for a year, when I checked the compression, it had 50 lbs in all three cylinders. I ran it with a fresh set of rings the next summer but the bore was on the loose side, ran ok though.

[rock]

Unusual for all three to be that worn and the same especially after you oiled them up. Must have felt a bit down on power last time out.

Rock

[stivov1]

it wont start, it has spark, I checked timing, even when I shoot starting fluid in cylinders, so fire at all

[stivov1]

I just went back and did another compression test, about 65 on all cylinders, its the same guage I used last week on my other motor that was at 135 on all cylinders.

[Raceman]

Assuming the battery is hot, the starter isn't dragging and the gauge is right it's low. For them to be uniformly that low to the point that the engine won't run makes it sound like it's been damaged somehow, like run hot, not enough oil or even wet and not dried out properly. Probably oughta' pull the head and take a look.

[stivov1]

thats what strange about these 60hp mercs, there is no head, its all one big casting. anyway, I may end up with the motor, so I'll probably tear it apart during the winter.

[phillnjack]

o would put a tin of powertune in the motor and let it sit.
get number 1 piston up the top by the plug and put loads of powertune type stuff in there to free the ring.
leave the motor on full tilt up and let it soak for a few days, then do number 2 the same then no 3.
stuck rings could be the problem.

the motor would not have ran that low when last used and to get all 3 that low with a bad thing happening is a bit of a million to one shot.
might have been 15 to 20 pounds out on atleast 1, but for all 3 to be the same it sounds like rings have got well and truly stuck in the grooves.

its well worth a try as like you say, you cannot get the head off so only complete rebuild will do it.
one thing you can do is put a little borescope camera in each plug hole and look at the sides of the bores.
just a cheapo borescope off the bay for about $15 is perfect, get the one with 6 lights and 6mm thick for whatever phone you have.
you can take pics and video and even sounds, so a very handy tool for the boat all round.....

[stivov1]

Ok, thanks for the reply! i'll give it a shot!!