Mercruiser 3.7 Head Gasket Replacement

[Old Yeller Boater]

guys....I think I already know the answer to this, but want to confirm the gaskets I'll need to pull the head and put things back together. I can get a " Victor Reinz Engine Kit Gasket Set" which includes the head gasket plus intake, exhaust, carb and etc gaskets.

What's your thoughts on the head gasket that comes with that set? Should I get a separate Mercruiser head gasket? If so, is the Quicksilver replacement adequate? I know you guys have said to only use the Mercruiser replacement, so just trying to confirm that various one's I'm seeing on the web.

thanks!

 

[Don S]

Re: Mercruiser 3.7 Head Gasket Replacement

Quicksilver is the retail store brand name of Mercury Marine (Mercruiser) parts. Stick with Oem parts on your engine and you will be a lot better off.

 

[stonyloam]

Re: Mercruiser 3.7 Head Gasket Replacement

Ditto on the OEM head gasket.

 

[Old Yeller Boater]

Re: Mercruiser 3.7 Head Gasket Replacement

I know you guys said to stick with OEM. I just wanted to verify the Quicksilver one is good. thanks so much for your input! Head removal starting this evening!

 

[Don S]

Re: Mercruiser 3.7 Head Gasket Replacement

Quicksilver is the retail store brand name of Mercury Marine (Mercruiser) parts.

Let me say that in a different way, same exact parts, different part numbers and packaging for retail stores.

 

[Old Yeller Boater]

Re: Mercruiser 3.7 Head Gasket Replacement

alternator, coil, distributor, throttle, intake manafold, cooling reservior, exhaust manafold all removed last night.

book says head gasket replacement is a 5.7 hour job. I think not!

I've got 1.25 hours in it so far and will have the head off this evening in another hour....if I work slow. Got a machine shop lined up to clean up the head. Then the reinstall starts. parts are on order and expect to have in another couple days. Got the Victor Reinz gasket set, but also found an OEM Mercruiser head gasket too. Amazing that it was going to cost $800 to do this work by the mechanic.

 

[Old Yeller Boater]

Re: Mercruiser 3.7 Head Gasket Replacement

Got the rest of the head removed last night. I'm heading to the machine shop at lunch today to drop it off. Sadly, it was not obvious by looking at the head and gasket that it was blown. What I did notice is that it's an aftermarket part. Victor Sainz specifically. I also received my new OEM gasket yesterday too. Merc was nice enough to stamp "front" on it. Interestingly, it appears that the previous gasket was installed backwards on the head and block. From my extremely limited experience, I'm thinking that's not a good thing, but how much impact would that have had on my problems?

Secondly, IF the head gasket was not the problem, are there any other areas I should specifically check closely? I'm going to replace the gasket between the exhaust manifold and the coolant reservoir. That's an obvious point were exhaust gas could get into the cooling system, although I'm not sure the pressures there would cause the symptoms I'm seeing. The other area would be the exhaust manifold, but only if it had a crack internally. Any other thoughts besides the gasket I'm changing?

thanks!

 

[Capt Ken]

Re: Mercruiser 3.7 Head Gasket Replacement

You did mark those pushrods so they go back in the same hole? The valves are adjusted according to pushrod length and the 3.7 comes in different lengths. And in case you didn't know, that head is just a Ford 460 head an being it has a closed cooling system, a regular head gasket will work.

 

[stonyloam]

Re: Mercruiser 3.7 Head Gasket Replacement

I also received my new OEM gasket yesterday too. Merc was nice enough to stamp "front" on it. Interestingly, it appears that the previous gasket was installed backwards on the head and block. From my extremely limited experience, I'm thinking that's not a good thing, but how much impact would that have had on my problems?

It could be. The head gasket should only be able to fit correctly one way. As I recall the "front" on mine faced up while the book says the "front" faces down. According to the photo in the book, the little bump on the gasket should be tward the back. Do you have the manual? If not here it is: http://boatinfo.no/lib/mercruiser/manuals/mercruiser8.html#/0

 

[stonyloam]

Re: Mercruiser 3.7 Head Gasket Replacement

, that head is just a Ford 460 head an being it has a closed cooling system, a regular head gasket will work.

True, but even though the regular head gasket will fit, it was designed to be used with a iron head on a iron block. The OEM Mercruiser gasket is designed to be used with the iron head on an open deck mercruiser Aluminum block and has features to address head gasket failure that the automotive gasket does not. For the few extra dollars IMHO it is worth it.

 

[Old Yeller Boater]

Re: Mercruiser 3.7 Head Gasket Replacement

yes, I did. each rod and rocker arm went into separate baggies and labeled appropriately. thanks for double checking me though!

 

[Old Yeller Boater]

Re: Mercruiser 3.7 Head Gasket Replacement

It could be. The head gasket should only be able to fit correctly one way. As I recall the "front" on mine faced up while the book says the "front" faces down. According to the photo in the book, the little bump on the gasket should be tward the back. Do you have the manual? If not here it is: http://boatinfo.no/lib/mercruiser/manuals/mercruiser8.html#/0

I have the "front" marked on my new gasket and will install correctly with regard to that. Up or Down I'll determine by the build of the gasket for what goes toward the exhaust manifold. In other words, the gasket isn't reversible from one side to the other, but it could mistakenly be reversed front to back.

And yeah, I've been referencing the manual for the work.

 

[Old Yeller Boater]

Re: Mercruiser 3.7 Head Gasket Replacement

I did also have a really good conversation with the guy at the machine shop when I dropped off the head. His initial check of the head and review of what I found with the original gasket helped me a lot. First off, having the gasket reversed front to back blocks off some of the passages differently. He said that could have resulted in the rear cylinders running hotter than the front ones. Explaining my symptoms to him, he didn't think that was the root cause of my problem though.

In looking at the head, he said it was not apparent that it was "blown", however, noting that the aluminum block factors in, he suggested two things. First, go ahead and work the head. clean up, maganflux to look for cracks, and plane the surface to be sure it's true, if needed.

Second, he recommended checking the block to be true. he said variation of more than .003 inches would mean the block needs planed, which means a complete teardown and not worth the $ in my case.

We talked about the other possibilities for the exhaust leak into the cooling system causing over-pressure. he said the other logical place is the gasket between the coolant reservoir and the exhaust manifold. Other than that, the exhaust manifold or coolant reservoir is cracked. I'm not thinking those are too likely, but will troubleshoot going forward. We thought a prudent first step would be to clean up the head, check the block, good gasket put on properly, and replace the gasket between the reservoir and exhaust manifold, which I plan to do.

If anyone has any other suggestions or things to check, please let me know.

Thanks again for the input you guys provide!

 

[Old Yeller Boater]

Re: Mercruiser 3.7 Head Gasket Replacement

Update: Head was cleaned up by the machine shop. he said it was in pretty good shape, but he did find the head was "dirty", he thinks from the previous head gasket install. He suspected that when the head gasket was last replaced, along with putting it on backwards, it appeared that they did not clean up the head surface. he said it *might* have had some input into the problems I'm having, but at any rate, said it was shoddy work by the previous mechanics. Along with it being clean now, he checked the block. It's got a bit of carbon, but appears to be straight. I'll clean up the carbon and put things back together this week. I'll be keeping my fingers crossed that it solves my exhaust gas problems.

Question....how likely would it be that my aluminum exhaust manifold may have some type of crack or other leak into the cooling system? As I'm thinking about other potential problems that could have caused my issues, that's the only other thing I can think. the gasket between the Exhaust manifold and the coolant reservoir appeared to be in tact, but it's being replaced as part of my repairs.

 

[Old Yeller Boater]

Re: Mercruiser 3.7 Head Gasket Replacement

Motor is back together with all new gaskets and it runs! I also got the temp gauge working now. Turns out it was a bad wire. I'm ready for a lake test this weekend to see how the coolant pressure goes.

Thanks to everyone for your input, thoughts and advice.

 

[Eric 3.7LX Alpha 1]

Re: Mercruiser 3.7 Head Gasket Replacement

Good let us know how it goes.

 

[stonyloam]

Re: Mercruiser 3.7 Head Gasket Replacement

Make sure to run it up to temp on the muffs and retorque the head bolts, BEFORE you take it for a test run.

 

[Old Yeller Boater]

Re: Mercruiser 3.7 Head Gasket Replacement

test went well. No more coolant bubbling out of reservoir, so much relief here. Temp gauge works well too.

as I monitored the temp out on the water, it seems that the cooling system on these boats is somewhat weak. I know I've got a good impeller and water flow. I also replaced the thermostat and coolant cap. Running it at high rpms, I could see the temp creep up to about 150-155. If I backed off and ran about 2800, it would settle down some, but not recover below the 145-150 range. The only time it got close to 160 was when I slowed to about 1200 to putt along.

does this sound normal for these motors, or should I continue to look for other problems?

 

[Eric 3.7LX Alpha 1]

Re: Mercruiser 3.7 Head Gasket Replacement

Those numbers sound good to me.

 

[stonyloam]

Re: Mercruiser 3.7 Head Gasket Replacement

as I monitored the temp out on the water, it seems that the cooling system on these boats is somewhat weak. I know I've got a good impeller and water flow. I also replaced the thermostat and coolant cap. Running it at high rpms, I could see the temp creep up to about 150-155. If I backed off and ran about 2800, it would settle down some, but not recover below the 145-150 range. The only time it got close to 160 was when I slowed to about 1200 to putt along.

It has a 160 degree thermostat and the normal lower range of the operating temperature is 165 degrees if it is operating correctly the temperature should never go below that range. I suspect your gauge is a little off. What is important is that the temperature remains fairly constant over the entire operating range (idle to WOT). Remember this is a closed cooling system and operates at a higher temperature than a raw water system.