2002 5,7 Mercruiser exhaust manifold keeps cracking - 5 times this summer

[mart284]

Heads are good and tested - will try to make better pictures with proper light. Those were done in the dark below the boat. Water part was pressure tested and each valve separately tested for leaks. IRL they are good and nice. On Friday will try to go to the boat and unwrap them and make better pics..

 

[cyclops222]

Well it sure looks like a VERY defective master mold at the manufacturer.
He is delighted with the recent demand for those manifolds.
Oh well.

 

[tank1949]

My setup looks very similar to the drawing attached - will go over it pipe by pipe once in the boat. Thanks!

Cyclops - Searay has rather big mufflers and it is not the issue with fast stopping, I am sure I have the issue with water flow around this one exhaust manifold - it started after the engine removal for the maintenance last winter. Just need to figure out, what is now different from last seasons...cracked manifold and engine bay

add y pipe flappers and/or increase exhaust manifold thickness by double the gaskets. Your manifold or head may not be perfectly flat. However, I suspect Y pipe shutters (flappers) will reduce cold water entering an exhaust system.

 

[mart284]

Went to the boat today and made a short clip of the heads, here you go:

Dropbox

www.dropbox.com

Should not be the issue that they are so bad. Will replace the springs. And all the contact plates are nice and straight - all measured and checked.

 

[cyclops222]

I give up on a repetitive same exact spot failure. Engines get REPEAT ...HYDRO LOCKS. I was on a cruise. I pulled the plugs and cranked t the engine to blow out water. 3 times on the cruise. No detectable damage to any of the engine parts.
Get a different manufacturer !!!

 

[mart284]

I give up on a repetitive same exact spot failure. Engines get REPEAT ...HYDRO LOCKS. I was on a cruise. I pulled the plugs and cranked t the engine to blow out water. 3 times on the cruise. No detectable damage to any of the engine parts.
Get a different manufacturer !!!

Sorry to disappoint you - Searay Sundancer has a muffler in the middle so there can not be hydrolock from water getting in from exhaust. Exhaust pipes are on the side of the boat hence sudden stop will not get the water in. I am not sure how other boats are done, but this IS NOT the issue here. No repetitive comments required from you on the same topic
PS - 2 different manufactures were used already on manifolds..