Inner exhaust Cover

[Jtp03819]

All,

Last year I acquired a 1960 Evinrude 18hp motor  model 15028. I’ve go through about 70% of the motor and decided not to take it apart any further once I took the head off since everything looked amazing. To be honest with you the motor runs great with the exception of it being cold blooded.  One thing I have noticed is that when I start it after it has sat for a while (1-2 hours or more) I see some milky oil blow out of the exhaust in to the water. I was wondering if this could possibly be a sign of an issue with the inner exhaust cover leaking water in the crank case. I do run Amsoil outboard 100% synthetic at a 24:1 ratio.  I have pulled the spark plug several times after running it at full speed for a while and also after trolling for hours. Every time I check them they seem to be dry and look like they are burning fine.  Any one have any thoughts or experiences with this?

To date I have replaced all seals and gaskets in the exhaust tube, replaced all seals and gaskets in the gear case, replaced the water pump, replaced the thermostat, replaced all ignition parts and rebuild the carburetor which believe it or not had the original cork float in it. I know there was also a ton of other trivial things that I have done that I’m sure no one wants to hear about. This motor was in great condition when I received it from the original owner who said that the motor didn’t get much use. I have attached a picture to show the condition that I received it in.

[Steve D]

First off, that’s a beautiful motor, great shape, congratulations on getting such a nice looking low hour motor.

Secondly, that gray foamy emulsion is somewhat normal on a lot of these older OMC motors. This subject comes up a lot on the AOMCI website:

https://www.aomci.org/forums/topic/gray-foam-lots-from-exhaust-outlet-1957-evinrude-10hp/

https://www.aomci.org/forums/topic/what-causes-this-grey-emulsion/

Here are a few comments from various ones, mostly Frank R.

Dark or milky oily exhaust housing emulsification after running the motor. It is oil and gas and exhaust mixed with cooling water in the exhaust housing and then drains through relief holes. Other than making a mess, it is normal with these motors.

It’s the unburnt fuel/oil mixed with water in the exhaust housing. The motor might be running a little rich, the carb needles might need to be leaned in a little, oil to gas ratio might be slightly high, use synthetic 2 stroke oil, try new plugs or next heat range higher, on motors with a thermostat be sure that is working properly. If the thermostat is stuck open the motor runs too cool..a hotter running motor will burn off fuel mixture better.

Even after all that you may still get some of that emulsion.

Other than making a mess, the leaks you mention are not a concern.

That milk shake is perfectly normal. It is the oil that you put in the gas. It has gone through the engine and done it’s job. From there, it goes out the exhaust and emulsifies with the cooling water that has also done it’s job. If the conditions are favorable (or unfavorable), it forms that foamy goo. Otherwise, it just goes on out unseen (except for a sheen on the water that also drives some people nuts).

[Steve D]

That color scheme is 1959. The transom clamp is the lighter blue which could be from the 1960 model. If that’s the case, that ID tag would lead you to believe it’s a 1960.  The paint appears to be original, so maybe it’s really a ’59 with the fuel pump conversion.

That’s basically the only difference between the 2 years…color scheme/decals and fuel pump.

[fleetwin]

Yeah, this doesn’t surprise me.  A common complaint, these engines have overboard drains that route excess fuel/oil mix down and out of the exhaust housing.  Like others have said, it is extremely important that the engine gets up to temp, the thermostat must be working properly.   Needless to say, this problem will be worse on engines that are idled extensively/trolled.  Always a good idea to run thee engine hard at WOT for a few moments at the engine of the outing in an effort to clean everything up.  From what you have written, the engine seems to be running well, so it seems unlikely that there is a water leak coming through the exhaust cover.  You might try a different brand of oil/fuel.

It is also a possibliity that you have a gearcase leak.   Perhaps the milky mess is gear lube mixing with water.   I would drain and inspect the gear lube to rule out this possibility…

[aquasonic]

Steve D wrote:

That color scheme is 1959. The transom clamp is the lighter blue which could be from the 1960 model. If that’s the case, that ID tag would lead you to believe it’s a 1960.  The paint appears to be original, so maybe it’s really a ’59 with the fuel pump conversion.

That’s basically the only difference between the 2 years…color scheme/decals and fuel pump.

Good observations!

There should be another ID welch plug on the starboard side of the block that will have the model and serial number stamped on it. It is possible that the powerhead was changed in addition to the transom clamps. If the powerhead was replaced with a 1960, the paint would also be a lighter shade of blue, it would have a factory fuel pump, and there would be no return line from the intake manifold.

 

Improvise-Adapt-Overcome

[Jtp03819]

Steve,

That’s great news that the emulsion is normal. I was worried the inner exhaust cover might have been leaking. You definitely know your motors. It is a 1959 when I order parts from marine engine I have to use the 1960 15030 model since they don’t have any part diagrams for the 1959 model. You as also correct in picking up on the transom clamp. When I received the motor the port side clamp was completely seized up and partially broken. The motor was used in saltwater and I tried for weeks to free it up and was unsuccessful. So begrudgingly I changed it out with a 1960 transom clamp that I had. You also pick up on the single hose fuel fitting and you are also correct there. I did add a fuel pump to this motor so I could use all of my existing gas tanks that I already had.  I did keep all of the original parts in case someday I wanted to put it back to original.  I have only recently started playing with outboard and so far have only rebuilt 3 1960 motors and this 1959. This is the first time I have actually seen the emulsion from the exhaust. These motors have become an addiction to me and I love rebuilding them! It’s a little bit expensive since I’m a big OEM person for parts but man is it fun.

Thank you for the information this will put my mind at ease and hopefully this motor will last for years to come.

[Steve D]

Like everyone else, I learn a lot reading everyone’s comments. And Fleetwin’s suggestion is good too for anyone not sure if they have a gear case leak. Even though you say you did the seals, it’s a good idea to check once or twice throughout the season by cracking the lower drain screw slightly and see what oozes out.

[Author]

Posts