MCM 140 cracked exhaust manifold

gscott87

Cadet
Joined
Aug 25, 2013
Messages
6
Ok I took a chance and bought a 1984 Four Winns Marquise 170 with a Mercruiser 3.0. Boat was trash when I got it. I'm a professional firefighter and decided to take it to the fire station and have a down time project. Gutted hull out rebuilt stringers all new floor. Total gut job. Started doing the upholstery and all that. Motor was not running when I purchased last year but a little work on fuel pump and carb all was well. Hence why I started to do the restore process. Ran it out of water a few times last summer and all ran fine. Been working on it all summer this year on cosmetic things and decided I better winterize. Started the motor and it ran like crap. Would not idle at all. Engine would run at higher rpm but ran very rough at low idle and would die. This is all done out of water on muffs btw. Messed with it again today and saw it was steaming or white smoke from exhaust. Long story short it is steam...I found a cracked exhaust manifold. I'm guessing last year when I winterized I did not get all water out of manifold due to chunks of rust clogging drain hole. Let me add this is my first dabble into restoring an old inboard boat. Cosmetically she is coming along nicely. But this manifold issue has me worried.

Should I repair this manifold by braising or just buy a new one. It appears that oil is a little milky as well. I would say that water has leaked into the valves. Oil level did not rise but it definately have some water in it.

I have no idea how long this boat had been setting prior to me purchasing but it had a 2014 sticker on it. I'm guessing thermostat and such may be bad because it looks rather rusty inside when hoses are removed.

Any insight on things I might need to look for that might be wrong besides the cracked manifold. I'm worried if I didnt cause it from leaving some water in it from last year what may have caused it then. I dont want to replace and the same thing happen again. Thanks in advance to any help I recieve.
 

Scott Danforth

Grumpy Vintage Moderator still playing with boats
Staff member
Joined
Jul 23, 2011
Messages
51,368
pressure test the whole cooling jacket side of the motor

buy a new manifold. they are a consumable.
 

Grub54891

Admiral
Joined
Jun 17, 2012
Messages
6,301
Yeah, I'd go with the pressure test also. I have the same motor, before I got it the po did the same thing. After a few tests, it was only cracked on the exterior. Cleaned it up and used jb weld to patch it up. Figured what could go wrong. After running it for the last four years, no milky oil. If you do have water in the oil now, it could be cracked internally, or it's condensation from not being run hard enough to burn it off. The safest bet is get new, but that's your call.
 

gscott87

Cadet
Joined
Aug 25, 2013
Messages
6
Thanks everyone I was leaning towards just getting a new one after reading they are suppose to be changed every so often anyway. Took it off yesterday. It was cracked on bottom and on outside.
 
Top