Whats the Differance OMC 165 hp GM 41L 250cid

Im wondering what is the diffe

Im wondering what is the differance between OMC and Mercruiser engine blocks?
Both seem to me are GM 4.1L 250cid 6cyl Blocks.
Same thing as a auto-truck GM-250cid block.
But only thing internal differance is a Marine CAM. If im wrong tell me the differance?

"OK.
I have the feeling that

"OK.
I have the feeling that the funds are tight on this deal.
I see you had a post where you wanted to use the old parts from the engine you have in a new block.
Up front this is a real bad idea and will end up costing you more in the end.
With that said.
Any chevy 250 six will bolt into the boat. If you use the old manifold you are ready to go. -Pre EFI

If you want to make it correct then the cam needs changed depending on what the engine is out of as well as the head gasket and freeze plugs.
Stainless steel head gasket brass plugs.

If it is a newer engine it will have low compression pistons so look for pre 1976 but after 1970 so it will burn unleaded fuel.
The truck engine is a better choice and 3/4 ton better yet.
The car engine is the same block and depending on the condition of the engine and how and where you use the boat should last at least 2 years without doing a thing to it. This does not include salt water use. Salt water is one season before the gaskets go if that long.

The OMC is a drop in, bolt on the manifold from the merc and go engine.

Hope this helps."

Thank You Guest.
My OMC Engin

Thank You Guest.
My OMC Engine has a crack at the water jacket;just under the manifold.
My options are Weld the Block. I have repair welded Larg Marine engines befor. And YES they are still in service.
But in this case its cheaper and better to just get another block
So with out spending alot for a Long Block. Plus I am a mechanic by trade I thought I would save a few Bucks. Rebuild with a MARINE Master Kit.
I just did not know if one GM-250 Block was better than the other for a Marine engine.
Since I did not have Casting Block number information. Not much info on the internet.
Plus I know my work and will feel alot safer if I do the work.
Again Thank You