Water in cylinder 1967 950 SS

[Bone fish]

Hi All! My wife's beloved '66 Searay has a recently rebuilt 1967 95 Mercury. The motor was done by a reputable shop and all new recriprocating parts (crank, pistons and con rods). The work was done in 2010 and the motor probably has 20 hrs since. Chesapeake Bay use, so its brackish water but flushed after each use, lift stored, warehoused in the winter.

After sitting two weeks it would not turn over on the starter. Using a breaker bar I wiggled the flywheel back and forth and got it turning, a little time and some oil and it cranked well without plugs. I got it started on muffs and it seems OK except I am seeing water on #3 & 5 plugs. Compression is 125-130 for all six. My guess is the water started the rings corroding making the motor tight.

I suspect the exhaust side cooling cover but though I would check here. #3 seems pretty high up for water coming into the exhaust, I would expect it in the lower cylinders. Could it be the head gasket? It doesn't look like cooling water flows through the head but I could be wrong. Is it possible to pressure check the cooling system for leaks to confirm before I take the cover off?

Any advice is appreciated! Trav

 

[turtles11756]

Re: Water in cylinder 1967 950 SS

johnsoldmercs.com

 

[emckelvy]

Re: Water in cylinder 1967 950 SS

Most likely source of water in #3 & #5 is from leaking exhaust manifold/gaskets. Since it's just been rebuilt, perhaps the gasket was improperly assembled, or there's a warped/perforated inner baffle plate.

I expect you're way beyond their warranty period, but with such low hours you might at least talk to the mechanic and get an opinion.

There is no head gasket so the only other possibility, besides coming from the exhaust manifold side, would be a cracked block. Not too likely with 2 non-adjacent cylinders leaking. But if it's spraying water inside the exhaust manifold area, it's entirely likely to be sucked-into the cylinders and throw water on the plugs.

Be sure to tilt the motor and oil-up those cylinders until the problem is identified & repaired. You don't want any more corrosion in there that has already taken place!

You may be able to get the manfold covers off in-place, but it's pretty tight at the bottom of the lower cowling. You may end up pulling the powerhead.

One last thought, I've seen plenty of "rebuilds" where the shop never touched the exhaust manifold cover/gaskets/baffle. If that's the case with your motor, I'd say it's almost 100 percent sure to be the cause of the leak. And if the exhaust side was never apart, use extreme caution since the bolts are likely to be stuck from corrosion.

Use a propane or MAPP torch to loosen them. If they won't break free, drill out the bolt heads as necessary and take them out after the covers are removed. At least then you'll be able to grab the bolt stubs with Vise Grips and heat directly.

You really really don't want to drill busted stainless bolts out of an aluminum block! :faint2: But once the hole is drilled, it's really really easy to install a Heli-Coil insert!

HTH & let us know what you find......ed

 

[emckelvy]

Re: Water in cylinder 1967 950 SS

dupl post, never mind!

 

[Bone fish]

Re: Water in cylinder 1967 950 SS

Thanks for the tip. The motor was rebuilt because the exhaust seperation plate had rusted through, leaked and rusted a couple of cylinders. hopefully the bolts will come out easily!

 

[jbjennings]

Re: Water in cylinder 1967 950 SS

Hopefully you don't have corrosion that's eaten a hole through the water jackets...... If so, time for a new block. You can likely tell with the exhaust cover off and with that combination, it isn't necessarily that likely.
Actually, I just repaired such a hole in a water jacket with a mig welder with 100% argon and aluminum spool gun---so it can be done and shouldn't be that expensive.

good luck,
JBJ

 

[Bone fish]

Re: Water in cylinder 1967 950 SS



This sure looks like a head gasket to me. Either way, looking at this and the exhaust cover it sure seems best to pull the powerhead. I don't think i willbe able to adequately inspect, clean or reassemble with it in place. How daunting a task is it?

 

[jbjennings]

Re: Water in cylinder 1967 950 SS

It's not that bad, but take lots of pictures to refer back to, and don't touch any of the timing stop screws. Also, be careful not to break any plastic parts!
Good luck,
JBJ

 

[Chinewalker]

Re: Water in cylinder 1967 950 SS

View attachment 215255

This sure looks like a head gasket to me. Either way, looking at this and the exhaust cover it sure seems best to pull the powerhead. I don't think i willbe able to adequately inspect, clean or reassemble with it in place. How daunting a task is it?

That's not a head gasket, per se, rather it's a water jacket cover gasket. The head is cast into the block on the old inline Mercs...

 

[carholme]

Re: Water in cylinder 1967 950 SS

Here is the parts list for your engine which is a model 1950107:

MERC 950 - Mercury, Mercruiser, Force, etc. Parts Lookup

See item 54 under CYLINDER BLOCK AND CRANKCASE ASSEMBLY.

Gerry

 

[Bone fish]

Re: Water in cylinder 1967 950 SS

Hi, I have finally removed the powerhead and the cooling covers on the exhaust side. The motor looks good, no rust on the rings or lower main bearing.

The diffuser is still in great shape, no cracks holes etc. I did notice the gaskets came off easily in a couple of areas and were well bonded in others. the loose areas were in the proximity of the cylinders getting wet, so i suspect leaks in the gasket areas. I also noticed the block and outer cover had not been well prepared, lots of pits etc.

Question 1, what sort of sealant should be used on these gaskets if any?

The outer cover has two small holes that had need repaired with an epoxy type material. The holes are 1/8" to 3/16".

Question 2, should i use epoxy and if so what kind?
Has anyone had luck with Alumaweld rods?
Is there somewhere i can send the part for a 'professional' repair?

Many thanks!

 

[bgc]

Re: Water in cylinder 1967 950 SS

I have used Aviation Gasket sealer on a heavily pitted unit. Have the holes welded or replace cover.