Cylinder Head Replacement

[jsurfwhite]

I have a 2000 356 Aft cabin with twin 7.4L Mercruiser gas inboard drives. The port engine needs a new, or rebuilt cylinder head. My mechanics are trying to source through Mercruiser, but tiiming keeps getting pushed out. Any ideas on other options to source a Mercruiser head?

Thanks,

Jim White
Owner Suture Self IV
2000 Carver 356 Aft Cabin

[bud37]

Have you considered a local engine rebuilder, they may be familiar with a marine 454 head......brass casting plugs etc.....

[tomschauer]

Hopefully others will chime in here.
But in my 40 years of wrenching on cars, trucks and boats, very rarely do heads need "rebuilt". If you rebuild the engine, you of course want to redo the heads, but unless you burnt or bent a valve the heads are usually ok other than oil seals. It seems to me inexperienced marine mechanics often say the heads need redone, and then the problem still isn't corrected. If you burnt or bent a valve, usually its was caused by a worn cam issue or water intrusion through bad manifolds, so that need to be addressed or you will be back to where you are now a bit to soon.
What was the problem that led to the head(s) needing rebuilt?
If you are down that path, as Bud mentioned, any local engine shop should be able to redo the heads for a gm 454 pretty quickly.

Best of luck to you, hopefully you are up and running soon!

[Viper]

What is it about the head that requires it to be rebuilt, bad valves, seals, springs? What lead them there, poor compression, leak-down test, performance, or....?

[jsurfwhite]

The original problem was exhaust leak. Found badly corroded, leaking exhaust tee, silencer on port engine. Replaced tee and hoses. Still had problem. Found cracked exhaust manifold on exhaust manifold on outboard side. Went to replace manifold. Found sever corrosion on bolts and manifold ports. Mechanic is saying we need to replace head. I will submit photos separately.

[jsurfwhite]

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[Viper]

You're lucky it wasn't worse, that's from the water jackets leaking into the exhaust and could have resulted in a serious engine failure. In a salt water application, you want to consider replacing raw water exhaust manifolds every 5-7 years or you risk having to replace your engines. I'd be replacing all your exhaust manifolds and check the other heads while you're at it.

[bud37]

If this engine was running good before, and by the looks of things from your pic, a competent rebuild shop can probably resurrect these after a cleaning and pressure test if that is what you are asking...but it all depends on the inspection after cleaning......check all that cost against a new refurbished 454 head.....IMO

[jsurfwhite]

Thanks for the replies. The engine was running well, so I avoided a major engine failure. Going with refurbished head. There are concerns from engine builder that the surfaces cannot be restored to seal well with the exhaust manifold. They are going off photos, so I realize it's not an exact assessment. I am working with a reputable boat mechanic team who warrants their work, so I am going with their recommendation.

[Viper]

Ya you need replacement heads.