Heres a good mystery one

[b0mbtrack]

Eng #OM640816 MPI 4.3
2003 engine year

Last September (2011) we had the starboard cylinder head go bad as it had a crack in it. It wasn't from winterizing because it was being used all summer long with no problems. We thought at the time it was from bad manifolds and risers, that water got into the cylinders from them going bad then turning the engine over cause the head to crack. So we did the starboard head and the manifolds and risers (both sides with the manifolds and risers). We also checked flappers but they were fine. So after doing that in september the boat was used fine till october when it was put to bed.

This year it was used all summer again no problems till september again. This time the port head is doing the exact same thing that the starboard side did last year. Keep in mind the manifolds and risers are brand new mercruiser parts and look to be in good condition and the flappers are still good. Also, both times the water didn't transfer to the other side of the engine. When the stbd head went last year the water stayed on that side, this time the port head went and the water is staying on the port side.

Any ideas what would have caused these cylinder heads to go bad like this? Like I said, last year we just assumed it was a set of bad manifolds and risers but now it seems like something else must have been going on. Anyway, we are probably just going to get a new engine but I'm just looking into what people think out of curiosity.

 

[Failproof]

Re: Heres a good mystery one

Salt water or fresh? Could be thin castings that finally corroded out. Some of the cooling passages that are not exposed to combustion pressures are suprisingly thin on some castings. Core shifts in the manufacturing process can make it even worse.

 

[b0mbtrack]

Re: Heres a good mystery one

Thanks that would definitely make sense. The engine is saltwater with a twin engine that has so far had no problems. Thanks again.

 

[Fun Times]

Re: Heres a good mystery one

Eng #OM640807 MPI 4.3
2003 engine year

Anyway, we are probably just going to get a new engine but I'm just looking into what people think out of curiosity.

If you do decide to buy a new engine from Mercruiser, you may want to have a look at post number 3 in the link below,

http://forums.iboats.com/showthread.php?t=304156

Good luck.

 

[NHGuy]

Re: Heres a good mystery one

If you decide to get the new engine obviously get the one with the e-coating salt water anti corrison treatment

 

[Bondo]

Re: Heres a good mystery one

Thanks that would definitely make sense. The engine is saltwater with a twin engine that has so far had no problems. Thanks again.

Ayuh,.... What, exactly, happened to the other head last year,..??

Ya said it Cracked, but Where,..?? 'n how is it spewin' water,..?? Where,..??

 

[b0mbtrack]

Re: Heres a good mystery one

Hey guys, thanks for all the good advice and info.

Bond-o, as far as where it leaked in the head I'm not too sure. I sent it out to the head shop and they just said it had a crack in it. I knew it was the head though because after I took off the manifold I could see the water coming out of the rear exhaust port where the valve is. The same exact thing is now happening to the other cylinder head, the water is dripping out of the rear exhaust port where the valve is. If it were the head gasket I think it would fill up the cylinder and come out the spark plug hole but I think the crack is higher and is why the valve port is filling up first.