1976 Mercury 1150 - Water Problems, Several of Them

[jtexnm]

Some will argue.----If the leak got worse ,then the risk is water getting inside the motor via carburetors.-----That could reduce the motor to scrap.----So you need to repair that now , if not sooner.

Ahh. I wonder if some JB Weld over the torn gasket would hold it until I want to lift the powerplant (several things I'd like to do and use it this year, hoping to avoid adding another if possible). I have a list of next year stuff. I'd like to add this to that if possible.

 

[jtexnm]

A related question: when I do pull the exhaust cover off, should I also replace the inner gasket?

 

[Chris1956]

Merc850 Depending on the year of the motor, and possibly the HP, some of those head water jacket bolts have nuts, or could use nuts, after you drill them out. There are a few on his motor near the bottom that are blind. The rest will need nuts or retap. That job is a real PIA.

Jtexnm, if you do want to remove the exhaust cover bolts, you will need to heat and spray them with penetrating oil as they cool. Using a hand impact driver is a good idea as well. A little prayer never hurts, as they have been in a long time, and will have some/lots of corrosion.

The inner water jacket bolts were epoxied in at the factory. They can be trickier to get out. If you do break some, and you most likely will, they need to be drilled out and retapped in a precision manner or the inner cover will leak. A drill press is a real good idea.

if it were me, I would caulk all the leaks, and run the motor. If you are getting water into the cylinders, that cylinder will not fire and you can detect it. Also, water will show up on the spark plugs as droplets. The spark plugs will also look like brand new ones on those cylinders with water present, as they get steam-cleaned.

I would source all gaskets and the baffle and inner water jacket cover before starting work. They may not be available.

 

[jtexnm]

Merc850 Depending on the year of the motor, and possibly the HP, some of those head water jacket bolts have nuts, or could use nuts, after you drill them out. There are a few on his motor near the bottom that are blind. The rest will need nuts or retap. That job is a real PIA.

Jtexnm, if you do want to remove the exhaust cover bolts, you will need to heat and spray them with penetrating oil as they cool. Using a hand impact driver is a good idea as well. A little prayer never hurts, as they have been in a long time, and will have some/lots of corrosion.

The inner water jacket bolts were epoxied in at the factory. They can be trickier to get out. If you do break some, and you most likely will, they need to be drilled out and retapped in a precision manner or the inner cover will leak. A drill press is a real good idea.

if it were me, I would caulk all the leaks, and run the motor. If you are getting water into the cylinders, that cylinder will not fire and you can detect it. Also, water will show up on the spark plugs as droplets. The spark plugs will also look like brand new ones on those cylinders with water present, as they get steam-cleaned.

I would source all gaskets and the baffle and inner water jacket cover before starting work. They may not be available.

Chris, that sounds like a big undertaking. Certainly intimidating. That's what I needed to know.

When you said I should source the baffle and water jacket cover, would you expect those to break? Sorry if I don't understand.

I'm not getting water in the cylinders, fortunately. Does this mean the inner jacket is good?

I checked all the spark plugs today. I also put in new spark plugs not long ago and the old ones were all very dirty.

 

[Chris1956]

The inner exhaust water jacket cover and exhaust baffle can rot out and leak water into the cylinders. On a fresh water motor, this takes a real long time. On a salt water motor, say 20 years.

However, you do not want to take it apart and see that you need one of these, and it not be available. I have epoxied a hole in the inner exhaust water jacket cover, and it worked. I junked the motor a few years after and it was still holding. Your results may vary.

If no water is getting into the cylinders, silicone those leaks and go boating. Black silicone is available.

Keep an eye on the spark plugs, especially the lower ones. If they get too clean you can be getting water into the crankcase via the lower crank seals.....much easier repair.

On a related note. The wiring harnesses on those motors are usually shot by now, if not replaced. Watch for insulation that falls off.

 

[Scott Danforth]

Gaskets last about 15 years. Your motor is almost 50.

You may have to go thru the whole motor and change all the gaskets

 

[jtexnm]

The inner exhaust water jacket cover and exhaust baffle can rot out and leak water into the cylinders. On a fresh water motor, this takes a real long time. On a salt water motor, say 20 years.

However, you do not want to take it apart and see that you need one of these, and it not be available. I have epoxied a hole in the inner exhaust water jacket cover, and it worked. I junked the motor a few years after and it was still holding. Your results may vary.

If no water is getting into the cylinders, silicone those leaks and go boating. Black silicone is available.

Keep an eye on the spark plugs, especially the lower ones. If they get too clean you can be getting water into the crankcase via the lower crank seals.....much easier repair.

On a related note. The wiring harnesses on those motors are usually shot by now, if not replaced. Watch for insulation that falls off.

Lots of great advice. Thanks for writing all this.

The first thing I did on the motor was heat shrink all the wires with crumbling insulation. There were a lot of them.

 

[racerone]

Did you try tightening the cover bolts ?

 

[jtexnm]

Did you try tightening the cover bolts ?

I haven't. My concern is that the same thing would happen as if I tried to remove them and replace the gasket, which is breaking.

 

[racerone]

Not going to try ??

 

[jtexnm]

Not going to try ??

The risk/rewards seems in favor of silicone patches if possible. Then replacing all gaskets at a later date.

 

[jtexnm]

At least in the case of the water jacket cover around the spark plugs, I read that the reason these leaks develop is that there are no bolts near the spark plugs. Only on the outer part of the cover. So tightening those wouldn't apply any appreciable pressure around the spark plugs, I think.

For the exhaust cover gasket, I believe I noticed a piece of the gasket hanging outside of the cover. Which means that if I can force some silicone inside that hole, it ought to hold.

Thanks everyone for all the great advice. You guys have taught me a lot of things about my old boat already.

 

[jimmbo]

I replaced the Gasket 3 times before the Service Manger took pity, ordered a new cover and gave it to me no charge. They warp if they get too hot, and even a new gasket leaks after a few runs. I installed them dry, I installed them with sealer, the Dry lasted longer, but the real fix was the new cover

 

[racerone]

Note ----it appears that you do not have to remove powerhead to work on these covers.

 

[jtexnm]

I replaced the Gasket 3 times before the Service Manger took pity, ordered a new cover and gave it to me no charge. They warp if they get too hot, and even a new gasket leaks after a few runs. I installed them dry, I installed them with sealer, the Dry lasted longer, but the real fix was the new coverView attachment 374092

Wow. Glad you got a fix!

 

[jtexnm]

Note ----it appears that you do not have to remove powerhead to work on these covers.

My thinking: many of the bolts are hard to access. I could get a wrench in there but I couldn't get an impact driver/gun. I'd rather do impact so that I am less likely to break the bolts.

 

[Chris1956]

As you have predicted, it is very much easier to remove the exhaust covers, with the powerhead removed. The lower cowl really gets in the way, and makes the use of an impact driver or socket wrench just about impossible.