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B100 Milky Oil - Head Gasket Looks Good, Now What?

C

code1p36

Regular Contributor
I have a B100 which I believe is a 70s model and found to what appears to be water in the engine oil. Drained it, filled it and ran it again and was milky again, so it doesn't take long to get water in there. It starts up easy, runs good and is a nice clean outboard. I immediately thought head gasket and had that apart fairly quickly since it was easy to get to. I thought it looked good. I have attached pictures of what I have so far. I read other posts about pulling the whole head but wanted to get some input to what you other experts see from the pics as I am more familiar with 2-strokes. There is quite a bit of carbon build up but don't suspect that to cause the water in the oil.

Can the little pump on the bottom of the camshaft cause water in the oil?

Where should I go from here?

Thank you!

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On the side of the block where the oil fill cap ( yellow ) is.-----Plastic cover has a seal ( item 14 ) that seperates water from oil compartment.------That round hole in the one corner has water going through it.-----Possibly warped cover or leaky seal there.------Note ---not an easy 10 minute job.---And I am not saying that it is the problem on your motor.------Look at the parts breakdown / exploded view.
 
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Ok, I will remove that black plastic cover that includes the oil filler cap and see what it looks like and let you know what I find.

Thanks.
 
Don't bother trying to reuse that cover. 99% of the time it has deformed and will NOT reseal.

The only other place where water can directly enter the crankcase is the small oring that "nestles" inside the engine block to oil case
 
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I have taken the powerhead off and everything looks pretty good to me. I did notice that hose I have in the first picture was pretty plugged with junk. Other than the plastic cover for the oil fill, head gasket and o-rings can I reuse the other gaskets, they all appear to be in excellent condition. I have included many pictures to where I am at so far.

JGMO - that o-ring (item 31) looks pretty good but wasn't as clean as I would like to see them so that might be the culprit, what do you think?

Thanks.
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Reusing gaskets or seals is always a crapshoot at best. I wouldn't try it but that's just me.

The hose is part of the crankcase breather and could account for condensate buildup in the oil.

If I had to guess.....and I do in this case.....it doesn't appear to me that oring 31 was leaking. But, again, I would caution you against reusing the gasket and seal.

This engine looks to be in very good condition and you have cleaned things up nicely. Be sure to check the thrust on the crankshaft before putting it back together.

Good luck.
 
I am going to buy all new gaskets and seals to be safe. Yes, this motor is very clean and it is all in excellent condition, inside and out. Here is a picture of the oil filler cover and found that milky oil concentrated right where the water and oil is separated by the seal so maybe this is the culprit?

It also didn't have a thermostat in it either! I just picked up this motor so all new to me.

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While you have this thing torn apart this far, if you plan on keeping it, I would definitely replace ALL seals the engines over 30 years old! It is really clean looking. I would also de-carbon the top of your pistons while you are in there. Thermostat should be replaced also, that is a regular maintenance item for me.
 
Definitely run a thermostat in it! Yes, it looks as if the oil fill cover may have been leaking. They are FAMOUS for distorting over time due to thermocycling and losing the seal. Replace it.

I also agree with de-carboning the combustion chamber, valves and pistin tops but you MUST be careful not to introduce scratch marks when doing so. Especially on the head and piston crowns. A strong solvent is ok like Berryman's carb cleaner but no acid and use plastic utensils only.

The 3m brand "roloc" power abrasive discs should also NOT be used for this job. Many mechanics have ruined many engines (and other things) using those types of "labor savers".

Good luck with that old, sweet, reliable outboard.
 
Ok, thanks for the replies on de-carboning, I was wondering... I have never done this before so it is acceptable to leave the valves in and just clean around them? I know it is important to make sure they seat correctly and didn't want any tiny pieces of carbon to cause issues.

Also, since I need a service manual and I am not sure which year it is what manual do you recommend, or which brand? If I recall correctly it starts with a B100-1006xxx so I believe in the 70s, are they all the same or similar from the older ones?

Thanks.
 
It's carboned up most likely because of being run cold. IE: no thermostat.

You can also decarbon using Sea Foam after she's running. A few good vids on You Tube show fair results.

Yes, you can leave the valves in place. You can also "lap" them if you're concerned about how they are seating. Again, You Tube is a good resource for studying how.

There is only one manual available for ALL the older twins....BF 75-BF 100-BF 8A.
I'll try to find the link for you.
 
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