Mercury 115...possible gasket issue?

[thefaulk]

I have a 1972 Mercury 115 stack 6 that I am having some problems with. I have posted once on the forum before and the help was very good and resolved my last problem. Now I could your help really bad again.

After cleaning the carbs, flushing the fuel system, changing plugs, wires and re wiring this old 115, I noticed in my driveway that one of the exhaust holes located directly under the cowling (I'm assuming this is what these are, there are two small holes that breath out exhaust there, the rest dumps out the propeller) the right one, to be exact, is dumping water out of it when the hose is hooked up and the motor is running. The left one doesn't have anything coming out of it except exhaust. I put it on the water after fixing all of the aforementioned items and it ran good for about three passes then, starting dogging really bad and steam started coming out of that exhaust hole. After letting it idle a little high for about 30 seconds, the steam went away, but it continued to dog out when throttling up and he steam came back when the engine came to rest after a run.

Any ideas on what this could be and also if there should be water coming out there???

 

[emckelvy]

Re: Mercury 115...possible gasket issue?

A few questions:

When you're running in the water, is the telltale stream strong?

Is the telltale hot, warm-ish, or cool?

Is the exhaust plate on the Pssgr (Port) side of the powerhead cool to the touch, luke-warm, warm, or does it get hot?

If the powerhead is running cool or merely warm-ish, and you always have a strong telltale of less-than-hot water, I wouldn't worry so much about what the exhaust reliefs are doing. And when you're on the flusher it sounds normal anyway, most of the exhaust pressure will go out the prop along with the majority of the water.

Anyway, let us know what the indicators are with your motor and then we can figure out if it's having cooling issues...............ed

 

[Chris1956]

Re: Mercury 115...possible gasket issue?

Faulk, Those square holes are for exhaust relief. It is not unusual for water and exhaust to emerge from them. It is also normal for water to come out of only one of them. The steam is what is not normal. You are overheating that motor, and it will be deadly to your pistons and cylinders.

I recommend you rebuild the water pump, replacing the impeller, gaskets and stainless steel wearplate.

 

[thefaulk]

Re: Mercury 115...possible gasket issue?

Okay, I had it out on the water again today (I only live about 8 miles from my favorite spot to run my boat) and It started great, idled great and ran strong until it got hot, then the power faded out and the idle became almost impossible to maintain. I felt the water after running it with a tuber at about 23 mph (3,100 rpms, roughly) and the water was very warm...on a scale of 1 to 10, I'd say probably a 6 or 7...the exhaust reliefs were a 7 or 8 and were steaming after that. When I let the boat set for a minute on high idle, the steam went away.

Then, after I got the tuber back in the boat and headed for shore I had it wound up to about 4,900 rpms for about 2 minutes. When I got back to shore and got it on idle (my mechanical advance was up about 1/4 of the way to maintain idle)
the water coming out was very thin, only shot about 3 inches from the side of the engine, had pockets of air in it (water, air, water, air) and extremely hot...probably a 9 on a scale of 1-10 and the steam had returned.

I didn't check the power head until I got home (about a ten minute ride) and the power head and mating plate to the head was too hot to touch, even after being out of the water and shut off for like 20 minutes.

Thanks for the quick responses by the way, I should probably change the water pump anyways...it's been about four years since it's been done and it's a done A LOT of sitting since then.

 

[thefaulk]

Re: Mercury 115...possible gasket issue?

Okay, I ran a couple of driveway tests on the boat to give you an exact on what the deal is here with the power head, exhaust cover and exhaust relief.

I started the boat with the hose on it and it started right up like usual, but when I brought it down off of high idle and went to the back of the boat, I noticed I didn't have a stream coming out at idle (900 rpms-ish) so I bumped the idle up to about 1,400 rpms and went back to see that the stream was now coming out, but was only coming out about 3 inches from the side of the motor. I let it run like that for about 5 minutes and felt the power head, exhaust cover and relief and they were all too hot to touch but the water was comfortable to put my hand under.

I did order a water pump kit last night, so I am going to replace that no matter what, but do you think I have any other problems?

 

[Yepblaze]

Re: Mercury 115...possible gasket issue?

Do a compression check.

By the sound of your description(s) you may have damaged internal components by overheating it.

 

[thefaulk]

Re: Mercury 115...possible gasket issue?

Okay, I did a compression test and this is how it read out:

Cyl. 1- 100 lbs.

Cyl. 2- 99 lbs.

Cyl. 3- 100 lbs.

Cyl. 4- 100 lbs.

Cyl. 5- 98 lbs.

Cyl. 6- 95 lbs.

When I took the plugs out, I noticed one of them had a small amount of white film on it with some water drops...I'm assuming I've got a bad gasket somewhere...

 

[emckelvy]

Re: Mercury 115...possible gasket issue?

The exhaust manifold gaskets are probably 'cooked' from overheating.

Other possibility if water was only on #6 is bad crankshaft seals but I bet it's the gaskets or a leaking baffle/inner port cover.

Just watch the manifold cover bolts when you pull it apart, you don't want to break stainless bolts in alum block! Use propane or MAPP torch to free-up the bolts.

 

[thefaulk]

Re: Mercury 115...possible gasket issue?

It actually was #5 I found the film on...that is a really good possibility and that's what i thought it could have been. I think I will put a new exhaust gasket on and whatever else needs to be replaced, too. Thanks for the advice.

 

[thefaulk]

Re: Mercury 115...possible gasket issue?

Okay, I took the water jacket cover and exhaust cover off and found water in the exhaust valley. It looked like it had been seeping in beside cyl#2 and draining down the block. After examining everything I found no cracks in anything, so I scraped the old gasket off and cleaned the two plates up.

But now I have another question. There is a piece bolted on in the exhaust valley that contains 3 exhaust holes for each cylinder. My question is what is this piece and could this be the cause of the water leak and not the baffle and top cover?

 

[thefaulk]

Re: Mercury 115...possible gasket issue?

Btw, this is a pic of the exhaust valley...the thing to the far left is what I'm asking about and you can see in the picture where the water was coming in.

http://i378.photobucket.com/albums/oo225/back_inblack/IMAG0146.jpg

 

[emckelvy]

Re: Mercury 115...possible gasket issue?

The cover is for passages that circulate coolant around the exhaust ports. If there are no signs of leakage from that cover/gasket, it's best left alone. The cover bolts are 'glued' in with "Resi-Weld" and you have to heat them up to even have a chance of getting them all out.

If there are no cracks in the cover, and its carbon coating hasn't been 'washed' off by any obvious leaks, I'd leave it.

One thing I did notice are the sides of the ports on the visible cylinder in the pic. They're pretty clean, are the rest like that or just that one? If it's just that one, better check it out very carefully to make sure you know where the water's coming from.

Hopefully you can tell from the spray pattern inside whether the water was coming from the covers/gaskets you've already removed......ed

 

[Superman1]

Re: Mercury 115...possible gasket issue?

I have a 115 HP mercury inline 6. I changed the jacket water cover gasket. When I did I put copper cote on the gasket and torqued to 12.5 ft lbs. the gasket squished out in spots. My book says 12.5 ft lbs is this correct.

 

[Yepblaze]

Re: Mercury 115...possible gasket issue?

This thread is over a year old.