Replacing Water Jacket

[Plainsman]

I'm going to be replacing the water jacket soon and was wondering if there is anything I should be wary of?
Or is it pretty straight forward? I do have the merc repair manual.
TIA,
Eric

 

[Texasmark]

Re: Replacing Water Jacket

Not sure what water jacket you are talking about. If you are talking about "the waterjacket" you are talking about the engine block to me.

If you are talking about covers, there is one over the pistons (top where the plugs are) and another 2 piece one on the exhaust manifold.

The former is a big problem. Latter two, main problem is being careful to not break bolts off and cleaning up corrosion from the alum covers.

If I were going to do that I would soak the screws good for a couple of days with the best penetrating oil I could find. (I use Kroil) and get a light duty impact wrench and set it to a light torque. Then just let it bump away till it breaks em loose. I do a lot of old farm machinery work and I am utterly amazed at the ability of an impact tool to loosen old frozen hardware without damaging it.

Just don't have the wrench set too high.....would defeat the purpose. Just keep increasing the pressure on it till you start getting results. Be patient and give them time to come out.

Mark

 

[Plainsman]

Re: Replacing Water Jacket

Thanks Mark,

I have a small amount of water coming out of the #1 cylinder and was told that it was the water jacket seal. Looking at the blow up pic of the motor, I ordered 3 new gaskets.

I can't copy the pic and don't want to put another website on iboats.

it's part # 721421

I know this is vauge as I have never done this before.

But i will soak the bolts for a week.

 

[AMD Rules]

Re: Replacing Water Jacket

Eric,

Just to clarify so I understand. The gasket referenced is the exhaust baffle gasket on the side of the motor.

You mention water out of #1 cylinder. Are you certain that water is actually inside the cylinder itself, or could it be coming out around the spark plug. It is not uncommon for the cover plate gasket to leak on the end, near the spark plug. When you remove & look at the spark plug does it have water on it? Is the piston steam cleaned & shiney?

Before you dig into the exhaust side (a lot of work), be sure you pinpoint where the leak is coming from. You may get lucky and only have an external leak from the end cover plate. In some cases they can even be sealed from the outside without replacing the gasket.

Where's the leak?

 

[J.L.]

Re: Replacing Water Jacket

Eric,
If you have water leaking around the spark plug, you simply have a cover gasket failure.
If you have water inside the cylinder, meaning you've found it on your spark plug after running, you are almost certain to have an exhaust plate leaking. If the motor has overheated it is very likely to be the inner exhaust plate inside the exhaust cavity mounted on top of the exhaust ports. These bolts are epoxied in place and will require direct heating to remove them. They should also be epoxied back in place when installed.
You should be able to find the source of the leak by following the carbon wash from the water. Look for steam cleaned areas in the entire exhaust cavity.
If you find the water leak to be the outer exhaust plate itself or its gasket, don't mess with the inner water jacket as you are risking damaging the plate by removing it.
You should be prepared to remove the powerhead for this repair. Get yourself a base gasket also.
Jerry

 

[Plainsman]

Re: Replacing Water Jacket

Thanks for the replys!
I had it running on muffs and noticed water leaking from around the #1 cylinder. The plug was not wet with water and there is carbon on the top of the cylinder.

 

[Chris1956]

Re: Replacing Water Jacket

Eric, It sounds like the water jacket cover around the spark plugs is leaking. If so, a bit of silicone caulk around the spark plug will usually seal it. You might keep your ordered gaskets until the exhaust baffle rots out, and needs replacement.

 

[Plainsman]

Re: Replacing Water Jacket

Chris,

So I just put some around the base of the plug and tighten the plug? What type of silicon? Marine grade?

 

[Chris1956]

Re: Replacing Water Jacket

Eric, I use the auto hi-temp silicone, although I doubt the area gets hot enough to warrent it. It can be helpful to mark the leaking area while running the motor and then stop the motor and dry it out and then silicone it!

 

[Texasmark]

Re: Replacing Water Jacket

"So I just put some around the base of the plug and tighten the plug? What type of silicon? Marine grade? "

The plug screws into the head which is an integral part of the block. The water jacket cover has a hole in it for each plug. Where the jacket goes around the plug (and would touch the head if it weren't for the gasket) is where the seal is; has nothing to do with the threads on the block/head or plug. However, you probably will get some on the plug when attempting to stop the leak.

But what's it hurting? I mean in only took it since '76 to leak this much. For what it's worth, I changed out that gasket on my '89 after about 7 or 8 years of use and it wasn't that bad of a problem. Got the gasket set from the local NAPA store as there was no marine dealer around here and it was B4 the days of www.

Mark

 

[Plainsman]

Re: Replacing Water Jacket

Thanks to all!!!

I think I will replace the gasket, seems the the best route to me.

 

[Chris1956]

Re: Replacing Water Jacket

Eric, Sometimes the 1/4-20 bolts that hold the water jacket cover on to the head are thru bolted with nuts. if so, it doesn't hurt to break them while removing them. The bottom bolt (if I recall correctly) is threaded into the block. You do not want to break that one. d

 

[Plainsman]

Re: Replacing Water Jacket

Thanks Chris. If I do break a bolt, is there any special strength bolt I need to replace it?

 

[lilmandavis]

Re: Replacing Water Jacket

make sure they are a good grade stainless. bad grade= rust. you dont want rusty bolts.......