OMC Upper and Lower Unit Oil Change. NEED HELP!

[WillWinchester]

I have a 1975 Larson runabout with a 6 cylinder chevy omc sterndrive. First boat I ever owned, the guy I bought it from took pretty good care of the motor, wiring is all messed up and jheri rigged but overall a decent boat. Just got the faulty trim solenoid working again and trimmed the outdrive down, next step is changing the oil. I need some assistance on the process of changing the upper and lower unit oil and what oil exactly to use. Have a pretty good idea but would like some advice from someone who would know more than me. Thanks.

 

[southkogs]

Welcome aboard Will:

On a '75 OMC you didn't trim the motor down, you tilted it. That's a very important distinction. The stern drive on an OMC Stringer is designed to be run in the full down position. If your boat has trim, the trim jack is on the front of the engine (perhaps mechanical and perhaps hydraulic).

Upper gear case can be your favorite marine gear lube - I used 80W-90. The drain/fill port is on the on the starboard side of the upper gear case, and the vent/dipstick is on the top of the drive.

The lower gear case will need to be Type-C gear oil because you're electric shift. There's a vent on the port side of the lower gear case below the anti-ventilation plate, and a fill/drain port on the port side of the "bullet" case just ahead of the prop.

 

[Chad Flaugher]

Probably stating the obvious here, but it is imperative that you fill the gear cases from the lower drain hole with a pump. Filling the unit (especially the upper gear case) from the check port can cause an air bubble that gives a false full reading. This can lead to catastrophic failure.

 

[Twainer]

I have yet to do this on my old boat. 1979 MT OMC w/351W. What kind of pump do you use to do this? It's hard for me to visualize how to do this since gravity urges you to do it the other way.

 

[southkogs]

Cheap one at the top HERE is what I use.