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Removing the head on a mercruiser


johnnugent's Avatar
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Join Date: Feb 2006
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11-27-06, 05:18 AM   #1  
Removing the head on a mercruiser

I am planning to remove the risers and manafolds on my mercruiser 454. Then i need to remove the head as i am sure I have afew bad valves. I did a compression test, the pressure in #1 cylinder was 120psi
#3 0 psi #5 30 psi #7 60 psi. the starboard side was fine at 120 psi all cylinders. I then plan to send the head out to be repaired.
The boat is a 1995 searay with 440 hours on the motor. I maintain the boat myself and it has always been kept up. It's been many years since I removed a head ( 1974 on a 427 corvette ) and I just wanted to know if anyone out there had done this and if there was anything I should watch out for. My main concern is the snapping of bolts and having something drop into the motor when the intake manifold comes off. I have a SELOC book to go by. When I do I need to remove the rocker assemblies before I send the head out ?

 
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thezster's Avatar
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11-29-06, 03:33 PM   #2  
Sounds as if it is possible you have a blown head gasket around the number 3/5 cylinders.... However - if you want to proceed with the head/valve work.....

As that Mercruiser is nothing more than a Chevrolet automobile engine with some aftermarket marine parts - you should be fine doing it the same way you did your 427. Take your time, take notes during disassembly - a digital camera is great for before and after shots to remind you how something came apart. Make your workplace as user friendly as possible - removing the engine cover completely for access - and cleaning out the bilge before starting to make finding that dropped "whatsit" easier to find.

You can leave the rocker arms in place - a good machine shop will reinstall everything for you to proper specs. Also - if you're going to do one head - then this is the time to do the other.

Make sure you buy marine grade head gaskets for reassembly. I would also replace the manifold bolts - both intake and exhaust - especially if you operate in salt water. Also a good time to do a thorough check of your exhaust manifolds for corrosion. 10 years is typically the time to replace them -especially in a salt water environment.

 
johnnugent's Avatar
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12-05-06, 05:50 AM   #3  
Removing the head 454

the head has been on the block for ten years. Any tricks to get the head off without causing damage to it? Also if I mark the distributors position to the intake manafold before i take it out, when i reinstall it it should go back to the correct location, right ?

 
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12-05-06, 06:55 AM   #4  
Just make sure you get all the head bolts/intake bolts/exhaust bolts out before trying to pry it off. I usually use a crowbar judiciously to break the head gasket seal loose - and the heads have always followed with no problem.

As far as the distributor - yes - mark it before you disassemble - and make sure your marks line up on the re-install.

 
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