Antifreeze Damage in my Mercruiser 3.7L 224 cid

[PCongiusta]

This week I went to start my 1987 Searay which has 3.7L - 224CID Mercruiser engine. I heard clanging when engine started and I discovered two bent pushrods. This was caused from antifreeze leaking into the cylinders from a cracked exhaust manifold. The two cylinders exhaust valves are stuck beyond repair, so I removed the head. Upon examination of the top of all 4 the pistons, as well as the cylinder walls, all are in pretty good shape. The worst is cylinder 4 and little in 3 where there is some pitting on the top of the cylinder head but you can plainly see the letters STD. Last year I suspect the cracked manifold happened, I know I ran my boat motor for no more than 4 hours that season.

I know any engine purest would say to do the job properly you need to rebuild the entire engine and I understand that.

My question is this, can I get by this boating season and hopefully a few more years to come, if I just replace the head with a new rebuilt, as well as a new Exhaust manifold and exhaust elbow?

Thank you for your input,
Paul C.
East Brunswick, NJ

 

[Eric 3.7LX Alpha 1]

Re: Antifreeze Damage in my Mercruiser 3.7L 224 cid

did you have any water or coolant in the oil? If the cylinder walls look good... I'd go for it, in fact I'd take that head to a machine shop and have them freshen it up instead of a new/reman one.

Did you get the new exhaust manifold/riser yet?

Oh yeah Welcome to the forum, lots of smart individuals here, and quite a few 470 owners as well :facepalm:

 

[Grub54891]

Re: Antifreeze Damage in my Mercruiser 3.7L 224 cid

I honestly cant give ya a good reply. I'll just say that I've seen more than a few that were pitted pretty badly,they ran/sounded just fine,had good compression,didn't use alot of oil. Alse seen just the opposite happen. I guess it depends on how much the motor wants to live! Some are fighters,some are not.
Grub

 

[Don S]

Re: Antifreeze Damage in my Mercruiser 3.7L 224 cid

My question is this, can I get by this boating season and hopefully a few more years to come, if I just replace the head with a new rebuilt, as well as a new Exhaust manifold and exhaust elbow?

Sure, if those are the parts that originally caused the problem. If they weren't the cause of the problem, then it will come back, and I'm not into guessing when.

 

[stonyloam]

Re: Antifreeze Damage in my Mercruiser 3.7L 224 cid

I agree with Eric (that is happening a lot lately LOL). I had the same problem with #4, head looked like it had been shot by a shotgun. My machinist (a guy with lots of 470 experience BTW) said "no problem. Replaced all of the exhaust seats and one valve, and all was fine. I would at least have the head checked out. Keep track of which holes your pushrods came out of. Straighten out the bent ones as best you can and take them to a Ford dealer and they should be able to match them for length. If you keep your original head then you should be able to reuse your good pushrods (if you are lucky they are all the same length). Use a OEM Mercruiser head gasket when you put it back together. Here is the engine manual in case you do not have it: Boatinfo - Mercruiser Service Manual nr. 8 - 1985-1989 - Mercury Marine 4 Cylinder Engines

PS: Get that oil out of there ASAP if there is antifreeze in it, the antifreeze will trash your bearings.

 

[Bt Doctur]

Re: Antifreeze Damage in my Mercruiser 3.7L 224 cid

So what cauded the crack in the exaust manifold, improper mix of A/F or just water in the block.#4 cyl damage is usually caused by a bad riser.

 

[PCongiusta]

Re: Antifreeze Damage in my Mercruiser 3.7L 224 cid

Eric and all, I am going to take your good advice and take the head to a machine shop, the owner said it will cost around $250-$300.
to rebuild the head. I also found, probably the last kit in the US for the exhaust manifold and elbow riser, they cost me around $1600.00 for
both parts. I am also waiting on some push rods, I bent 2 from the two stuck valves. So with any luck I'll be back on the water by the first week of August, just in time for some good crabbing.

You guys are great and thank you so much for your good advice and support.
If anyone knows a good procedure to adjust the valves after I replace the head I appreciate it.

Thank you again,
Paul C.

 

[Bt Doctur]

Re: Antifreeze Damage in my Mercruiser 3.7L 224 cid

there not adjustable per se, the push rods come in different length`s

 

[stonyloam]

Re: Antifreeze Damage in my Mercruiser 3.7L 224 cid

If anyone knows a good procedure to adjust the valves after I replace the head I appreciate it.

The Dr. is correct, you adjust the valves by installing pushrods of the correct length. That is why I suggested that you take your bent rods to a Ford dealer to make sure you get the correct length. Once you have installed the push rods you simply need to torque the rocker bolt nuts to the correct value in the CORRECT sequence (the valves MUST be closed) per the manual.

 

[PCongiusta]

Re: Antifreeze Damage in my Mercruiser 3.7L 224 cid

Thank you to everyone for all your great advice. And after a new Exhaust Manifold kit, two new push rods a rebuilt head, and about a $2000.00 to pay for all three, my boat is running like new! This week, I put 6 hours on my engine and it starts and runs better as good
as when I bought the boat new 25 years ago. Thank you again for giving me the information and confidence to fix the boat myself.

 

[Eric 3.7LX Alpha 1]

Re: Antifreeze Damage in my Mercruiser 3.7L 224 cid

Glad to hear she's purring like a kitten again..

Where did you happen to get the exhaust mani kit from... There has been a few on here since your last post looking for one, and like you mentioned they're disappearing faster than the Twinkies at the local market.