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.