What oil for 78 3 cyl 70 HP

[olemana]

Just drained oil form a pair of early 70's 70 HP 3 Cyl lower units.
One had few drops of water, the other had what appeared to be 85W90.
MY 75 service manual calls for an OMC number oil or if that is not available DEXTRON ATF.
In later years was a running change made to 85W90, or was that added to hide leaking seals?
Both lower units can be rotated and shifted by hand.
This is a 2 to make 1 deal, puting best parts on same engine!!

 

[HighTrim]

Re: What oil for 78 3 cyl 70 HP

Which year exactly? Or do you have a model number? There was a switch in the 70s

 

[olemana]

Re: What oil for 78 3 cyl 70 HP

Lower unit 1 is from engine model 70875C serial J0008422 was dry after sitting 5 years
Lower unit 2 is from engine model 70478M serial J0005675 Had 85W90

Thanks for your help!

 

[HighTrim]

Re: What oil for 78 3 cyl 70 HP

It is recommended to use 80-90 outboard gear oil, it has additives to protect the lower if you have water intrusion. I personally use the BRP full synthetic. Always replace the washer on the vent and drain screw as it is the #1 cause of water intrusion.

On the older electric shift motors, use Premium Blend Type C for electric shift.

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