OMC 175 Low compression in one cylinder bank Head or gasket failure

"Hi,

I recently purchased a

"Hi,

I recently purchased a 1977 twin OMC Formula. The units are 302 Fords (OMC 175).

The first time I took it out, I noticed some blow-by coming from the starboard engine breather cap. The engine wouldn't stay running for more than 15 minutes or so, then it would die. It would restart 30-45 minutes later or so, then die again after running 15 minutes.

I just got through doing a compression test on the starboard engine and the results have me a bit puzzled. The starboard cylinder bank (Cyl 1-4) has even compression, 120# across all four. The port side (Cyls 5-8) reads:
#5 - 60, #6 - 90, #7 - 90, #8 - 110. So, I know 5-7 are dead. I squirted some oil in the suspect cylinders and it made no difference in compression measurements. Since the starboard side has even compression and I have one good cylinder in the port side, I'm assuming rings aren't the culprit.

I'm leaning toward head gasket failure or cracked head at this point since the bad cylinders are adjacent to each other. Oil looks clean as far as I can tell. I guess I won't know until I pull the head, but does anyone have any ideas?

Any ideas would be appreciated!!

Thanks!"

"maybe gasket. maybe valves. l

"maybe gasket. maybe valves. leakdown test would tell without pulling head, but it's gonna have to come off anyway. rock and roll."

"well if u did the oil test an

"well if u did the oil test and no increase, u know it is not the rings

did u do a comp test with it at WOT?"

"Yep, WOT...I'm going to p

"Yep, WOT...I'm going to pull the head on Saturday...I'm betting (and praying) it's just the head gasket.

Thanks!"

"I would have taken the Valve

"I would have taken the Valve Cover off, and did another comp test while inspecting for mechanical defect.Foamy Oil from leaking Head Gasket? (Do these engines have hydraulic lifters? I cant recall, being a Dodge engine fan.)If no mech. defect is noted, then squirt the oil (this is with only the tested cyls' spark plug removed.
I'm new at Marine Engine configuration, being a Drag Racer for many years.

S."

also make sure u have all spar

also make sure u have all spark plugs out also when doing the test