1989 Mariner magnum 40 4 cylinder, oil/water out of exhaust port

[Smokemetallic]

Hi,
When loading my boat up yesterday after 2 hours of trolling and some short high speed runs, I noticed a oil/water mixture seeping out of the above waterline exhaust ports on my engine. Never noticed this before, did not look right. Engine runs excellent and is in over all excellent shape. The seepage looked like gearoil combined with water, much like the milkshake you get in the oil pan when a car blows a cylinder or head gasket.
When I got home, I immediately drained the lower end, no signs of water intrusion, and proper amount came out.
I then refilled with fresh gear case oil and ran engine on clamshell with hose, no sign of any oil/water mixture coming from exhaust ports.
Any ideas? It would seem gear oil is getting from lower end into exhaust port some how.
Much thanks for any advice.

 

[Maxz695]

Re: 1989 Mariner magnum 40 4 cylinder, oil/water out of exhaust port

could be a few things 1) There may be a leak in the exhaust base or gasket there seeping exhaust into the rear portion of the plate. 2) Could be leaking crankshaft seals letting mixture combine with water intake in the LU or again through the exhaust plate into the water port section of the plate. Could be the exhaust cover leaking exhaust into the water port at the baffle or divider plate but this usually creates and overheat type situation as exhaust gasses will heat up the water to a much higher temp then normal. (Check the pee stream temp and see if it,s just luke warm If hot there may be a leak there. The hose that leads to this section usually runs from the side of the base plate under the powerhead then through the fuel pum where it exits through those ports. This water should be mostly cool to the touch. The pisser comes of the top block section of the rear water jacket and should be warm and the water coming out of the prop should be hot as expected due to mixing with the exhaust. There is obviously a leak somewhere letting oil fuel mix with the water. Is there oil mixed with the TT stream? How about the prop? Some should be expected there but not a ton of it. If no water was found in the LU It more than likely isn,t gear oil. Taking the LU down for inspection may have to be done or a pressure test of the LU is probably better. It appears the engine may have sustantial carbon build up wich can cause gaskets to fail. I would reccommend a good decarb (Sea foam) after the repairs are made. Hopefully the block hasn,t got a crack in it and usually not but still a possibility.

 

[ajgraz]

Re: 1989 Mariner magnum 40 4 cylinder, oil/water out of exhaust port

Any chance that's 2-cycle oil rather than gear oil?

If you did an usually large amount of trolling, then a lot of 2-cycle can end up pooling in the bottom of the crankcase. Maybe some of that leaked past the crankshaft oil seals, into the exhaust adapter plate, past the adapter plate gasket, and into your cooling water.

Of course, if all that's true, then your adapter plate gasket needs attention, because that means water can conversely get into your crankcase in the opposite direction. Any evidence of water in the cylinders? (Sludge on plugs, or at the other extreme, "steam-cleaned" looking plugs?)

EDIT: Max and I posted at same time.

 

[Maxz695]

Re: 1989 Mariner magnum 40 4 cylinder, oil/water out of exhaust port

I saw that. My carbs may be here tonight arrived but not marked out for delivery. I,ll write you later tonight

 

[Smokemetallic]

Re: 1989 Mariner magnum 40 4 cylinder, oil/water out of exhaust port

Thanks for the advice so far. I just went out to the garage to verify compression. 133,136,132, and 127 psi top to bottom cylinder. Plugs looked fine with no steam cleaning or excessive buildup. The motor was sitting in the garage trimmed all the way down since I ran it on the clamshell yesterday and noticed milkshake coming out of the hub:

As far as the other questions, the tell tale stream was lukewarm when running it on the garden hose, and exhaust was much warmer. Didn't notice excessive oil thru the prop, but obviously there must have been. Good compression leads me to believe that the crankcase seals are good. So are we looking at the leaking gaskets or a crack?
Also, no excessive trolling was done yesterday.

 

[Maxz695]

Re: 1989 Mariner magnum 40 4 cylinder, oil/water out of exhaust port

Being that it is not limited to the one section that leads to the rear ports, and is in fact leaking out of the exhast to the prop, I would remove the powerhead and do a complete inspection of the block area the exhaust base plate as it appears to be from that section be it corrosion crack or a bad gasket. As long as the pee stream did not get too hot to touch after running to the warm up I would think the exhaust port and baffle plates are OK. Is there any indication of the milkshake coming out of the TT? If not the waterpump indicates it,s clear of the oil and the LU should not be suspect.

 

[Smokemetallic]

Re: 1989 Mariner magnum 40 4 cylinder, oil/water out of exhaust port

Thanks for the advice. Will begin power head removal this evening to check for leaks at adapter plate gasket, and will remove exhaust manifold cover and baffle plate to determine source of leak.

 

[ajgraz]

Re: 1989 Mariner magnum 40 4 cylinder, oil/water out of exhaust port

Plugs not showing anything unusual is very good sign that water may not be intruding into the crankcase or cylinders. It probably is, as Max suggests, exhaust gunk getting into your cooling water at the exhaust adapter plate. VERY common problem in these older Merc's.

Thanks for the advice. Will begin power head removal this evening to check for leaks at adapter plate gasket, and will remove exhaust manifold cover and baffle plate to determine source of leak.

I'd start with the adapter plate gasket. You'll likely wind up destroying it while removing the powerhead--which kinda sucks because you may not be able to diagnose whether that was actually your issue until replacing that gasket and running it again. (Of course, look for cracks in the plate or powerhead, or corroded mating surfaces, etc. that could allow the leak.)

Only if the above does not fix you should you consider taking off the exhaust cover and baffle, IMO.

 

[Smokemetallic]

Re: 1989 Mariner magnum 40 4 cylinder, oil/water out of exhaust port

Just finished getting everything apart. Couldn't really tell if adapter plate housing gasket was leaking or not. Can you guys narrow it down whether its the exhaust baffle or adapter plate from these pics. No cracks anywhere I could see but still need to lean everything up. Lots of oil/water everywhere.
Top view of adapter plate gasket after removing power head:

Adapter plate removed and looking down into trans tunnel :

Bottom view of power head:

Will start cleaning everything up and look for any obvious cracks/defects. Did not see any compromised gaskets.

 

[ajgraz]

Re: 1989 Mariner magnum 40 4 cylinder, oil/water out of exhaust port

Wow, that looks like a lot of gunk. Does it smell like raw fuel/oil, like burnt stuff (exhaust gunk), or neither?

 

[Maxz695]

Re: 1989 Mariner magnum 40 4 cylinder, oil/water out of exhaust port

It appears that the end cap oring crankshaft wear sleeve or endcap seals are shot. You may be able to coax out the end cap without undoing the intake manifold. The endcap should slide off the bearing easily. I,m not seeing the puller holes in the end cap. Hopefully it will come off easilly after unbolting it. Water in this area Pic #3 and pic #1 is mixing with seeping fuel from the seals oring etc. Water is also entering the block and being spit out the exhaust. Becuase the plugs are not steem cleaned and the engine is not sputtering or overheating and has good compression I think it is limited to this area. What leads me to the encap senerio is the water port section of the base still has the gasket in tact and no oil intrusion is present that i can see whatsoever. <EDIT> To me the wearing of the seals there could be the result of something happening to the lower end cap, be it warped cracked etc (Inspect it well) or the lower bearing is NG letting the crank turn off center wearing the seals and creating an out of round motion allowing oil and water to mix. This would in time also effect the bearings of the rods wristpins and center main reed blocks. Replacing the seals my do the trick but you my also find yourself doing this again if it is the bearing and it,s not replaced as well. Just my opinion.

 

[Smokemetallic]

Re: 1989 Mariner magnum 40 4 cylinder, oil/water out of exhaust port

So you're guessing that the pto side crankshaft bearig is going which has compromised the endcap seal. Is there a practical way to pressure test this motor without having to fabricate a block off plate for the exhaust and intake? I'm guessing its easier to just change the seal. Would rather not put everything back together only to have it leak again or worse if a crank bearing is suspect.

 

[Maxz695]

Re: 1989 Mariner magnum 40 4 cylinder, oil/water out of exhaust port

after removing the end cap simply spin and rock the bearing to see if there is play. There should be very little to none. The visual of the bearing will tell you if this has been occuring for some time. Look for rust on the outter case and inner ring of the bearing.<EDIT> I don,t know if there is enough room to get a bearing puller in there if it is bad. There are ways I,m sure to get it out without having to dismantle the case. Soeone here may have ideas. I know they speak of heat and cold to expand the bearing to where it will come right off. Maybe you have a marina around you somewhere that can assist you with the removal. I use a 20 or 22 MM deep 1/2 inch drive socket to install it back on but again heating it in an oven should expand it to simply set on the shaft. DO NOT TRY TO HEAT THE BEARING WHILE IN THE MOTOR WITH A FLAME> Just a precation. I,m sure you not dumb but sometimes some people do things thye shouldn,t. Just my opinion.

 

[ajgraz]

Re: 1989 Mariner magnum 40 4 cylinder, oil/water out of exhaust port

I agree that signs are pointing to lower oil seal failure; but again, does this muck smell like unburnt fuel/oil?

If you are going to pull the lower end cap, I say you might as well dismantle the case. You can do this without pulling the rotating assembly out, separating conn rods from the crank, or removing the pistons from their bores. It will make pulling the endcap for the re-seal job 10x easier, plus you'll be able to visually confirm condition of all the bearings, reeds, etc. inside the crankcase (looking for signs of water intrusion), as well as better see the condition of the oil-seal sealing surface at the bottom end of the crank, as well as also check the condition of the upper endcap oil seal. It won't cost you that much more in materials (assuming there are no additional problems), just a new upper endcap o-ring and some loctite flange sealant (or equivalent) to re-join the case halves.

 

[Smokemetallic]

Re: 1989 Mariner magnum 40 4 cylinder, oil/water out of exhaust port

After a quick break for shotgun deer season, I'm back to troubleshooting this motor. Much thanks to everyone's advice so far.
Before tearing the case half off to remove the endcap, I figured I would check the exhaust baffle since I have a full gasket set coming. All appeared normal to me, with no signs of anything out of the ordinary.

Pistons and bores looked fine, no signs of water intrusion , moderate carbon buildup on the piston domes, mild original crosshatch still showing from the factory, no major scoring or gouging.
Also to answer an earlier question, the oil water mixture doesn't smell strongly of unburnt fuel, more like normal 2 stroke exhaust smell.

 

[Maxz695]

Re: 1989 Mariner magnum 40 4 cylinder, oil/water out of exhaust port

be sure not to use to much sealant when putting the baffle and cover on as there are water port holes that go from the outter exhaust cover into the rear cover and if they get sealed it will cause a running hot or overheat situation. You may get away with just the gaskets if the surfaces are that good which you stated they seem to be.

 

[Smokemetallic]

Re: 1989 Mariner magnum 40 4 cylinder, oil/water out of exhaust port

So I just wanted to update this thread with the conclusion of fixing the motor. I heated the exhaust baffle up to 250 degrees in the oven to check for cracks, found none. Reinstalled with new gaskets.
Turned my attention to the lower unit. As soon as I took the water pump housing off, it was obvious someone had run it dry at some point. Melted end on the impeller blades, plastic housing got so hot it melted . This had compromised the o ring underneath the pump, which allowed lower unit oil to make it into the driveshaft housing. New pump and impeller and I thought the problem was fixed.
After 10 minutes of idling , same symptoms as before. I was getting confused at this point.
Tore the lower off again, made a homemade vacuum tester with a hand pump , no leaks. Made a pressure tester, obvious leak at the shift shaft seal/bushing. Changed it out, cleaned everything up, reassembled.
Engine runs perfect now, extremely happy. Also rebuilt and cleaned carbs and fuel pump.

I suggest everyone who wants to do their own work, just bought a second hand motor, etc, build or buy a vac/pressure tester.
Many thanks to the people who advised me in this thread.