Cracked exhaust manifold 305 engine

[Slo mo]

My manifold is cracked and engine is overheating. I replaced the head gaskets and need info on how to fix this problem.

 

[Bondo]

Ayuh,..... Welcome Aboard,...... Merc,..?? OMC,..?? Volvo,..?? Some other,..??

 

[Bondo]

this is a 1981 weldcraft sunhatch with a 305ci motor and mercruiser outdrive.it started running hot and steam blowing out.there was water in one piston and bent a push rod.I had the heads resurfaced and a valve job as well.upon starting it up when the thermostat opened water was dripping out of the manifolds both sides and steam blowing out. the elbows to the manifolds were very hot.I shut it down so i would'nt blow a gasket again.both manifolds have cracks and dripping slow.

Ayuh,..... Did you pressure test the block for cracks,..??
Have you changed out the raw water pump in the drive,..??

 

[Scott Danforth]

My manifold is cracked and engine is overheating. I replaced the head gaskets and need info on how to fix this problem.

you buy new exhaust manifolds

if the manifolds cracked, any rubber bits in the exhaust will have also burned up, such as coupler hoses and flappers

the source of your overheat is the raw water pump. fix that

 

[Bt Doctur]

water will always be flowing thru manifolds no matter if the T stat is open or closed. As posted start with the impeller in the drive

 

[Slo mo]

Ok I will start with the impeller. Can the cracks be repaired or do I need to replace them. Also where can I find manifold replacements.

 

[Scott Danforth]

Ok I will start with the impeller. Can the cracks be repaired or do I need to replace them. Also where can I find manifold replacements.

you can not fix a cracked manifold

you can buy from your local Mercruiser dealer, thru iBoats, or various on-line locations. if you buy from other than Mercruiser, buy Barr