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Hello and Thanks in advance for your help I have a 1988 Yamaha 90 hp I changed the lower unit oil today. The oil that was inside looks very good not a sign of water at all. I pumped in almost one quart ( I let it drain for two hours) and plugged the top hole and added two short pumps of oil in to compensate for the little that came out the top hole.I plugged the bottom drain and some oil started to come out where the water gets picked up to cool the motor. Some came out on both sides. Is this normal? did a seal blow? I did not add that much more? If this is an issue is this an expensive fix if I remove the lower unit and bring it two a shop.Thanks again.

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Had the same thing happen this summer on our Evinrude, noticed gear oil coming out the water intake screens when the engine was tilted up. Checked and I did have water in the gear oil and the source was a bad bearing carrier o-ring.

When you're refilling and new oil comes out the top hole, temporarily put the top plug in, remove the fill tube from the bottom, install the bottom plug, then remove the top again and top off with a squeeze bottle until some more flows out. Replace the plug and you're done.

At this point, pull the top plug out again and see how much oil comes out, you may have overfilled. But the seals should hold up to more pressure than that regardless, so to be safe, it's worth looking into further. You may have found a potential problem right before it happened!

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Thanks for your response I am going to run the motor on ears. Then check for water in the lower unit. I had the water pump replaced by a shop last year and they pressure tested it OK . it had very little use last year . I guess I am wondering if you can blow a seal by two very short pump of oil with the top hole closed?

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I can't speak to Yamaha, but the final PSI numbers for the Evinrude test are 16-18 PSI if memory serves. Granted, that's using compressed air, and at the time of your extra pumps, your gearcase was filled with fluid... I'm not sure if the two very short pumps you mentioned would develop that kind of PSI and force the remaining air out through the top seals? That's what makes me think you may have spotted a problem early.

I'd suggest getting the correct level first and then running it as there needs to be air at the top to accommodate expansion from heat, otherwise you may well see a leak regardless if you are overfilled.

BTW do you know if the seals were ever replaced at any point?

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I finished completing some of the pre season things I wanted to do plugs fuel separator filter filter on motor and I had a new fuel pump so I put it on it did not need it but it was easy enough. I did open the top plug and some oil came out so it corrected its level like you were saying. I started the motor on muffs and ran it for a while in forward and reverse. I let everything dry out and changed the oil and checked for any sign of water everything looked good no water. I filled it again just until the oil came out the top hole and closed it off. I raised the motor up and down and no oil came out the water intake grills. I think I am still going to take you advise and have my local shop pressure test it. I leave the boat in a slip here in NJ and I want to have some peace of mind knowing gentlemen will not lead to additional failure. But maybe I will get lucky. The 17 Ft Montauk with the 90 hp Yamaha is suck a great combo I need to keep her going. The gentlemen I bought the boat from keep it in great shape and used it very little but I do not have any service history of seal replacement on regular maintenance. I did have the lower unit pressure tested last season all way good. Thanks again for all of you assistance.