1990 8hp Merc Oil question

[AKA_CJ]

Hello, is it necessary to run a 50:1 fuel ratio in the tank on these motors or is their an oil resovoir in the motor that does the necessary mixing?

I've been running the 50:1 ratio and after every use there is a gross milky substance that leakes out from in the propellor.

Thanks,
Chris

 

[AKA_CJ]

Re: 1990 8hp Merc Oil question

It's actually a 1988. Serial #B340137.

Thanks,
Chris

 

[fishhunter]

Re: 1990 8hp Merc Oil question

Hello, is it necessary to run a 50:1 fuel ratio in the tank on these motors or is their an oil resovoir in the motor that does the necessary mixing?

I've been running the 50:1 ratio and after every use there is a gross milky substance that leakes out from in the propellor.

Thanks,
Chris

The white milky substance would be water mixing with the lower unit oil . Iam not a professional but I have read it is common for water to get in the lower unit but if it is visibly leaking you may need to rebuild the lower unit because the seals must be leaking excessivly. I personally have never checked a lower unit that didnt have SOME water (milky oil) drain out of it but it should not be leaking from the prop. It would probably be a good idea to drain and fill the lower unit oil before and after a trip and check to see how much water drains out . Also most lower units have a small magnet on the bottom fill plug .Be sure and check the amount of shavings on the magnet , clean it then the next time you fill the unit examine it again. If you are getting a lot of shavings then the water is probably diluting the oil too much and casusing excessive wear on the gears.
Disclaimer : Iam not a Mechanic I only know from my personal experience and reading posts in this forum.

 

[Texasmark]

Re: 1990 8hp Merc Oil question

Lower unit oil that is milky, chocolate color, yellowish, contains water. Water in the lower unit is a killer. If it is leaking out around the prop remove the prop and observe the rear prop shaft seal for evidence of the contaminated oil. If present then seems a resealing of the lower unit is in order. There are seals for shifting, drive shaft entry, prop shaft exiting, and seals on the fill and drain screws. The lower plug (drain) usually has a magnet in it if your engine has a magnet at all.....some do, some don't, and you can buy magneted plugs on here.

However, if it is not coming from around the prop shaft rear seal, it could just be residue from oil that is added to the gas mixing with water, and coming out the exhaust, especially in the colder months where incomplete combustion can be a problem and is perfectly normal.

One more however, if you remove the drain plug, especially if the engine has been sitting upright for some time, and water (the goo mentioned) comes out first then you can pretty well figure on seals being bad.

HTH,

Mark