Mariner / Yamaha 9.9 2 Stroke Gear Oil Issue ???

[LongIsland]

Hi I recently purchased a Yamaha 9.9 & mariner 9.9 2 stroke, both motors in running condition & both lower units are completely identical. I set them up side by side on stands and have begun some routine maintenance starting with draining the gear oil. One came out a yellow mustard color and the other pitch black. I've heard the mustard color means I have water in the oil but i'm not sure how easily this problem can be fixed or where it might be coming from. Also I can't seem to figure out what kind or brand of gear oil i'm supposed to go out and get to fill them back up. Any help at all would be great, kind of lost.

 

[jerryjerry05]

Re: Mariner / Yamaha 9.9 2 Stroke Gear Oil Issue ???

Water in the oil.You need to pressure test the unit.It's possible it came in from the screws,or from a seal.
GOOD oil is the key.You can use any 90wt.But Mercury oils have additives to prolong life and are better.

 

[Texasmark]

Re: Mariner / Yamaha 9.9 2 Stroke Gear Oil Issue ???

Ditto on water in the oil and find out where it is entering. If your engine with the milky oil is fairly new then one could feel that the drive, shift, and prop shaft seals are intact. That only leaves the washers that seal the fill and drain plugs. I always use new ones when removing the screws for routine maintenance or inspection.

On a pressure test, you could submerge your lower unit in water and using your fill adapter from your oil lube container, screwed into the drain hole, take an air hose and put the regulator on about 10 psig, connecting the air hose to the end of the oil fill hose (rather than having the lube container attached). Bubbles tell the story.

WW sells marine grade Quicksilver and Pennzoil oils for 2-4 cycle engines and their lower units. I wouldn't use anything else because they are specifically designed to stay tacky and stick to metal parts in the LU. On the one that's milky, I'd ensure that the engine was vertical,drain and let it drain for a couple of days. Then fill with fresh oil and run the engine long enough to get the oil fully distributed. I'd use the old screw gaskets for this. Drain again and fill with fresh oil, sealing with new gaskets.

HTH,

Mark

 

[LongIsland]

Re: Mariner / Yamaha 9.9 2 Stroke Gear Oil Issue ???

Thanks for the advice, i'll hopefully be able to tackle the issue this week so i'll report back. And just to clarify, any 90w gear oil will do the trick?

 

[Texasmark]

Re: Mariner / Yamaha 9.9 2 Stroke Gear Oil Issue ???

Thanks for the advice, i'll hopefully be able to tackle the issue this week so i'll report back. And just to clarify, any 90w gear oil will do the trick?

No, not just any 90 gear oil, MARINE gear oil. It has special additives required in marine environments to allow it to stick to metal parts thus isolating them from water contamination, should water enter the gearbox, which happens more frequently than one would like....especially for the owners who fail to keep their engines properly serviced.

Mark