cracked exhaust manifold on 4.3 v6 mercruiser

[dlogvine]

I started the engine Mercruiser 4.3 v6 on the boat I recently purchased (1985 Larsen). The engine (at least some parts of it, not the block itself) and outdrive I was going to put into my newer 2005 Larsen boat, which has no drivetrain. So this engine appears to run (surprisingly since it was not ran since id guess 2012). But I also found out that one of the freeze plugs has popped out and there is a mini crack in the exhaust manifold. Most likely it happened when the previous owner forgot to winterize the engine and left some water in the engine. Since I live in Phoenix this does not happen at all here, but the boat was in Flagstaff, where in winter the temperature goes below the freezing point. So the question is, is there any way to seal or weld this little crack on the exhaust manifold (I have an access to various welding machines - MIG and TIG welders, plasma cutter) or should I just buy a new exhaust manifold, they go for about $180 on ebay for GLM and a bit more expensive for Sierra or Mercruiser replacements? Thank you.

 

[Rick Stephens]

I would guess it would be a sad tale of woe if you tried. But why not? Small cracks aren't that hard to weld up if you find someone who has done cast iron before. My bet is it will leak or crack again.

 

[Scott Danforth]

a few things

if a core plug was pushed out, most likely the block is cracked

1985 is 6 generations of motor older than what would have came in your '05 not to mention the drive is not a gen 2

none of the brackets, pulleys, etc will work with newer motors

so do the next guy a favor and document everything your doing on your frankenstein motor.

cracked exhaust manifolds are junk. trying to weld them up is a fools errand.

 

[dlogvine]

Scott, im using a 1993 non vortec block to replace the old engine, i checked out, these blocks are using the same brackets, pulleys, etc. As for the outdrive, as long as i can put an old gen1 transome plate on the newer boat, im not overly concerned with that.

 

[dlogvine]

And ill just buy a new exhaust manifold. Should i look for mercruiser or sierra manifolds or would GLM do?

 

[Scott Danforth]

I would look for a Barr or Osco prior to GLM