1991 3.0 OMC Cracked Block Questions

[HMA_1920]

Working on a new to me 1991 3.0 OMC, don't really know the history of the boat or how it has been winterized in the past. When I got the boat it had water in the oil so I changed oil, pulled manifold and found a nice 6" crack. I "repaired" the crack rigged up a unit to pressurize the block and put some air in her. Found a few little external leaks on hoses and fittings and such, once I got all those sealed up and was 99% sure I had no more external leaks I pressurized to around 18 PSI. After 60 minutes I was down to 12 PSI. Internal Crack? not near enough of a leak to be able to hear it leaking through the plug holes or head or anything. So what do you guys think, internal crack or no? Thanks in advance and this forum has been a huge help in the past.

 

[Bondo]

So what do you guys think, internal crack or no?

Ayuh,.... Welcome Aboard,..... Probably got a crack somewhere, but you can fire it up, 'n try it,.....

If it Is freeze busted, you'll need a 1990, or newer long block to fix it,....

 

[HMA_1920]

I think I will, I was hoping being a small leak like that maybe its not an internal block crack. anything else to check before I put it together and run it?

 

[Bondo]

Ayuh,.... Is the motor in the boat, or on a stand,..??

My best Guess for an internal crack, is inside the block, 'bout opposite the drain plug,....

If the water entered from the manifold, it hada seep past the rings, so that cylinder oughta be rusted up,.....

 

[HMA_1920]

Motor is in the boat still, don't have a scope but cylinders do appear a little wet, not sure if its just condensation or what. Like I said don't really know the history of the boat, I personally have not had the boat running on muffs or in the water so have no idea when or where the water came from. Will put it back together today and run it on fresh oil and see what happens. when these motors crack do they normally leak on the muffs or just under a load warmed up, or not that predictable?

 

[Bondo]

or not that predictable?

Ayuh,..... You've got it,..... Usually, but not always,....

 

[HMA_1920]

Just put it back together, flushed the oil once and filled her back up, ran it for about a half hour, never did get up to temp, just idled cause I was on muffs and gained zero oil and see no water in it, looks like new oil still. Think I may be ok or may it leak under a load?