Milky Oil in 15HP Johnson 4-Stroke

I have a 2003 Johnson 4-stroke that has a recurring milky oil problem. I bought the engine about a year ago used. I thought at first that I had tilted the motor wrong when loading and water had entered through the exhaust valve, but when I was down in Baja over Christmas, I was very careful to only load and store the motor with the correct side facing up. I probably put 10 hours on the motor running WOT and trolling. When I got home, the oil was really milky. The problem is, the motor ran great. I had tested the compression previously and both cylinders were right around 50 psi, to spec. I fear I've got a cracked block, but I'd appreciate any other advice anyone cares to give. Thanks.

Re: Milky Oil in 15HP Johnson 4-Stroke

here is a discussion on that. http://forums.iboats.com/showthread.php?t=158085

Re: Milky Oil in 15HP Johnson 4-Stroke

Thanks for the response. It's interesting reading, but I think my problem goes way beyond that. My fuel and operating environment is in an area with very low humidity...typically 10 - 40%. 60% is unusually high. Combustion is not a likely source of water under my operating conditions. My other buddy boats don't have a problem. The water droplets I collected from the oil was salty. The oil was REAL milky this time, not just a bit off color.

Re: Milky Oil in 15HP Johnson 4-Stroke

not good, but not up on 4 strokes. could be head gasket like one a car, that blows from the cooling system.

Re: Milky Oil in 15HP Johnson 4-Stroke

Agree with Tash, start by having your gaskets tested.

Re: Milky Oil in 15HP Johnson 4-Stroke

Yep. I'm hoping that replacing the head gasket works. I can handle that. Replacing the block is something I'd rather not spend my time doing. Problem is that the engine runs good. I'm hoping the leak is small and that the water leaking through the had gasket builds up only slowly so that performance isn't significantly affected.

One thing I noticed was that the squirter on the cooling system had bubbles in it. I hooked up a piece of clear tygon to it and I could see them. I'm hoping that the bubbles are exhaust gases that are entering the cooling water stream during the pressure cycle. I tried collecting the gas in a flask and smelling it, but the volume was small. I had the motor connected to flushing ears and not submerged, so air could have been entering from other sources.

We'll see. Thanks for the input and anyone else who has any words of wisdom....please chime in.

Re: Milky Oil in 15HP Johnson 4-Stroke

Not sure about wisdom...but two Comments:
1) If the water is salty, you need to solve the mystery ASAP as a salt solution circulating inside a warm engine is a recipe for disaster (although since all my boating is in fresh water, I may be over stating the case)
2) Is 50 PSI compression really to spec? Sure sounds low to me....and would be absolutely consistant with a head gasket leak...which would also be completely consistant with coolant (sea water ) in the sump.

Re: Milky Oil in 15HP Johnson 4-Stroke

It sounded low to me too, but the Mfr.'s manual said 57 psi is spec. I don't remember what it was exactly....I'll measure it again, but as I recall, the compression was right-on. I'm going to pop the head and replace the head gasket anyway. I've flushed the sump about as well as I can to get rid of the salt.

Re: Milky Oil in 15HP Johnson 4-Stroke

Why not try a leak down test first that will tell you if your head gasket is not sealing

Re: Milky Oil in 15HP Johnson 4-Stroke

How do you do that?

Re: Milky Oil in 15HP Johnson 4-Stroke

you will need a leak down tester from your local auto store or borrow one and follow the instructions in the kit,but basically it fills the cyl with compressed air and you watch and listen for leaking air to pin point your leak.

Re: Milky Oil in 15HP Johnson 4-Stroke

I finally resigned myself to the fact that I was going to have to take the engine apart. One Saturday when it was nice, I tore into it. I had both the Seloc and Bombardier O&M manuals for reference. What I found was pretty much what I had expected. The results of my failure analysis follows. I won't be able to water test the thing until my next Baja trip over Memorial day and I'll confirm or deny the efficacy of my fix then.

Tests indicated that both the cylinders and water jacket on the head were tight. That's what I figured, as no power loss or erratic operation was observed. The oil in the 15hp Johnny is stored in an oil sump in the mid unit of the motor. A cut metal shim gasket separates the mid unit from the powerhead. On one side of the mid unit, two channels pass through it to the powerhead. One carries water from the water pump. The other carries exhaust gasses to the lower unit. Both the OEM and Seloc manuals say that this gasket must be sealed well and that sealant must be applied to both sides of the gasket and the mating surfaces, among other places. Close inspection of the areas beneath the old gasket revealed etched aluminum, which to me indicated that salt water had contacted it. If this was sealed well, only black silicone would have been there, as it was in adjacent areas. The factory didn't apply enough silicone.

Both the OEM and Seloc manuals say that this gasket must be sealed well with the legendary Triple Bond 1207B. Good luck trying to buy that. None of the boat stores here carry it....and San Diego is not exactly a town without maritime supplies. The boat mechanics that were hanging out at my parts store said to use Permatex Ultra Black gasket sealant.

So, I bought a new gasket set, popped the head gasket for kicks and giggles, given the fact that I was already in there anyway. The head gasket did not appear to need replacing. So I wielded my torque wrenches and put the thing back together. It runs great.....in my yard, but it always did. It needs to be run at WOT for hours to see if it leaks or not, but I'm pretty confident I sealed the channels properly. I'll report back after the next shakedown cruise, but I wanted to post this, as it's an unusual cause for milky oil that might help someone else out.

Re: Milky Oil in 15HP Johnson 4-Stroke

I just got back from my place in Baja. I put several hours on the engine and the oil is crystal clear. The problem was a leak in the water channel as it passed through the oil pan gasket. The gasket was not sealed properly at the factory. Make sure you use adequate sealant to seal this channel off when you're replacing that gasket. A more detailed description of the fix was described in my previous post. This response confirms that my analysis of the problem was correct.

Re: Milky Oil in 15HP Johnson 4-Stroke

Great to hear you solved the issue. I think we have all learned something from this thread.

Hey everyone. I am having the same problem with my 15hp Johnson. What is the name of the part and/or part number that you replaced? Thx for this post. It has been very helpful.

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