Water Leak, opinion needed

[tedder]

I've got a water leak and need help diagnosing.

Motor is a 1996 Mariner 115 2 stroke.

Started the motor today for the first time this season after a winter of storage.

Motor started fine, idled fine, p'd water ok but I noticed a small water leak coming from the lower left corner of the motor. I took the engine cover off and determined the water to be coming from the lower left corner of the engine/cylinder head cover.

The leak is at the lower left corner of the cylinder head cover.

Questions I have are.... what is likely the cause of the leak? is it a simple gasket re and re? or could something be cracked? will the leak get larger/can I use the boat or should I fix it first?

Thanks for the help.

 

[tedder]

Re: Water Leak, opinion needed

anyone?

 

[emckelvy]

Re: Water Leak, opinion needed

That's not the cylinder head. In fact, this motor doesn't have a cylinder head, the cylinders are cast integrally with the engine block. The cover at the rear, over the spark plugs, is the cyl block water jacket cover. This is normally where a cyl head would be found.

What you have indicated as leaking is the exhaust manifold.

Typically a sandwich consisting of an outer cover; gasket; inner exhaust baffle; another gasket between the baffle and block.

One thing I've seen on these is that the 'sandwich' compresses with heat expansion cycles and the gaskets 'squish', causing the manifold bolts to lose torque. This can eventually lead to leakage.

It's also possible gaskets have dried out and begun to leak.

Very simplest repair would be to check and see if the bolts have loosened up. If they have, re-torque the bolts to specs and see if that stops the leak.

If not, you'll need to remove all the exhaust manifold bolts, pull the outer/inner covers, clean up all sealing surfaces, and reassemble with new gaskets.

No sealer is required on new-style Merc gaskets but I like to use a very thin coating of Permatex #3 Aviation-Style gasket dressing on the bolts. This seals out any salt, alkali or other type of corrosives and will ensure that the bolts will never sieze up.

Note: your motor looks like it's run in fresh water so there should be no issues with the bolts coming out. If you have to use more than normal hand force removing any bolt, STOP! This bolt requires extra attention or it'll likely break.

Use a combination of heat (from a propane or MAPP torch, available at any Lowe's or Home Depot, etc) and penetrant such as PB Blaster to help loosen up the reluctant bolt. Worse case, drill out the bolt head to get the cover off rather than breaking a bolt to remove it. Then you'll have something to grip onto when you apply heat directly to the bolt.

Anyway, that's the most extreme case, I'd bet tightening up the manifold cover bolts seals up your leak. Be sure to check the cover for cracks i.e. freeze damage and replace if that's the case.

HTH & let us know how it turns out.........ed

 

[tedder]

Re: Water Leak, opinion needed

Excuse my ignorance with the cylinder head issue and thanks for the clarification.

I did check all the bolts, tightened the leaking area, ran the motor and still had a leak. Took the cover off and the issue was as you said, the gasket had dried out.

I had only removed the outside cover and not the inner gasket as it seems the leak was a result of the outer gasket. My issue now is do I replace the inner gasket as well despite the fact it seems it wasnt the issue. I guess I might replace the outer only and see what happens?!?!

Will also inspect the cover carefully for cracks, I didnt yesterday.

Cleaing the surfaces is a pain, almost finished it last night, will need another hour or 2 tonight. I used Laquer Thinner and a plastic scrapper.

Problem now is Merc no longer sells the gasket. Local shop is trying to locate one!!!!

Thanks for the information

 

[emckelvy]

Re: Water Leak, opinion needed

My vote would be to replace the inner gasket also. You've already found the outer one to be deteriorated, imagine the inner one is just as old and also is subject to more heat and exhaust pressure than the outer gasket has ever seen.

Also, you've broken the "sandwich" and released all the clamping force that was holding the old assy in place. The old gasket is not as likely to seal once reassembled.

Unfortunately, if the inner gasket leaks it's more than an inconvenience. The water will spray into the cylinders, and this as you can imagine is usually not a good thing!

Seems funny that these gaskets would obsolete already but I guess you never know anymore. Anything to get you to buy a new motor I suppose!!!

The gaskets might still be available in the aftermarket so have your shop try a Sierra catalog or check online.

P.S. scraping gaskets does S*ck!! Good idea using a plastic scraper, greatly reduces the possibility of gouging the somewhat delicate aluminum surfaces.

G'luck...........ed

 

[rwunstel]

Re: Water Leak, opinion needed

I've repaired two of these in the past week. Both were gasket problems.