Yellow gear oil

just picked up a 2001 90hp honda, engine seemed to run fine, took on water for test run, brought home, went to change the oil in the lower unit and it was yellow and smelled rancid. Seller told me he wasnt sure when the gear oil was last changed. I'm figuring i'm getting water in the lower unit. Gonna pull anyway to change the impellar, and have a manual on order, but any advice would be appreciated.

Well, I'm sure I'm not telling you anything you don't already know when I say water and oil don't mix. If you suspect there is water intrusion then let the drained 'substance" sit in a glass jar and watch for the inevitable separation of the two.

It actually sounds more to me that someone maybe put something in there that doesn't belong. Petroleum based hypoid gear oil doesn't go "rancid" but I'm not sure about synthetic gear oils. It could just be that syn oil was used and never changed. Just hope it wasn't WESSON cooking oil! You never can tell sometimes when you buy used.

It would probably be a good idea to take the prop shaft holder assembly out and have a look inside the transmission and then pressure/vacuum test upon reassembly.

Good luck.

Wesson...oh my...HAHA. Someone out here says any oil is better than no oil, but wesson.... Anyway, pulled lower unit, the o-ring on the underside of the waterpump is dried and cracked, may have never been changed, but who knows. Now it will be, good idea with the glass jar, its sitting in the drain bucket now and still seems to have the same color and consistancy, and i cant picture it emulsifying to the point where it wouldnt separate.

So I ended up talking to the shop that had serviced the engine over the past 5 years, they use yellow oil and he said its normal to have a foul smell after a season of use. Who knew....

Well, I learned many moons ago, from someone much wiser than myself, that one thing you cannot argue with is success. It may look wrong, sound impossible, feel outside the bounds of reality and stink to high heaven. But, if it works.....whatchyu gonna do? It works!