OMC 3.0l with water in the oil

[BUZZ8609]

I got a boat from a relative for almost free, and when i started it up in the driveway I see its got a crack in the block and was leaking.I patched the outside crack and started the engine up again and then checked the oil, and it has water in it, milkshake looking. I plan on pulling the engine to see if the heads are Ok , but I am not sure what type block i need to replace the one on the 3.0L cobra OMC.Can anyone give me some idea is it a Gm or Ford? The boat is a 97 caravelle, can you use the block froma auto/truck and fit it up to the heads ? Any help would be greatly appreciated.
Buzz

 

[jasper813]

Re: OMC 3.0l with water in the oil

The 3.0l is a gm block.
I have heard people say that it is the same as the 251 "iron duke" and some say it the same as the pontiac 253. Honestly I'm not sure of either.
Good luck

 

[ezmobee]

Re: OMC 3.0l with water in the oil

It's a GM but it is not, contrary to popular belief, the "iron duke". Look for a 3.0 marine engine. Check here: http://www.rapidomarine.com/

 

[BUZZ8609]

Re: OMC 3.0l with water in the oil

I thought it was the GM , and I will look for the marine block.I saw one on craiqslist in my area, for $300.00 , guess I better have it checked for cracks before paying for it, what do you guys think?
Appreciate your input!

 

[BUZZ8609]

Re: OMC 3.0l with water in the oil

I have a chance to buy a used 3.0 l GMC engine out of a older model boat, this boat is a 70's model walk thru .My question is will this engine match up with the motor mounts on a 97 3.0L and will my stern drives drive shaft fit up with this engines coupling? Trying to do this on the cheap otherwise my boat is not worth pumping alot of money into.
Thanks:redface:

 

[Howard Sterndrive]

Re: OMC 3.0l with water in the oil

if the 1970's engine comes with flywheel and coupler, I think it can drop right in.

otherwise, crossing the 1990 dateline *might* cause a minor issue for the coupler
The crankshaft bolt pattern changed in or around 1990 on the 3.0L
The parts are available to connect it in that case anyways, so not a big deal

Also, some pre-1990 flywheels had threaded holes to accept the newer triangular couplers.
The other difference might be in head porting and how it matches the manifold.. if you're planning on using the 1997 manifold
again - you can do some leg work and get parts to make it work.

 

[HT32BSX115]

Re: OMC 3.0l with water in the oil

Look any engine over you find very closely.... the blocks frequently crack inside as much or more than outside.....

If you get one with the head and other accessories on it you can easily pressure check it.

Good luck,


Rick

 

[BUZZ8609]

Re: OMC 3.0l with water in the oil

I went to look at a 3.0 L merc cruiser , it was a 1972 model , when I compared the accessories locations, (water pump, exhaust manifold, oil filter, distributor, it appears that the accessories are on opposite sides.If the distributor is on the right side on the OMC its on the left for the Merc. If I wanted to pull the merc engine and use the block with my OMC head, and oil pan, can the block be changed end for end so my accessories stay the same as they are now or do I need to look for OMC engines only?
Second question , how can I do a pressure check on the engine, since most of these guys claim the block is good, but the engine is not set up to run with water through it to make sure?
Thanks
for any help.