New drain screw + new gasket+ old gasket = a little water in new gear oil

1996 Mariner 175 Magnum EFI - Serial OG360900

Got the boat and motor about a month ago. Changed the lower unit gear oil and replaced the drain screw, vent screw and both gaskets around screws.

Afterwards, got to thinking that I had 2 old screws but only 1 old gasket. I guess I assumed it fell out and I didn't notice it.

3 weeks later (after running the boat about 5 times...never any runs longer than about 5 minutes at a time...maybe 2 hours total on the motor) I check the lower unit oil and notice it is extremely dark with a little discoloration.

I immediately drain the oil and begin investigating.

That's when I find the old gasket in the drain plug under the new gasket. So obviously this is where some water got in.

I removed the old seal and all pieces of it and cleaned off the new gasket real good too. Cleaned the hole, and made sure there were no pieces there - then re-filled the lower unit with oil.

I have not ran it yet - had planned to run it, then drain the oil again and re-fill it with new gear oil, and then depending on what kind of shape the drained oil was in - go from there.


Is this the proper procedure?

Hopefully I caught it before it caused any damage.

Any advice is welcome, thanks.

Sound like your on the right track. If you find water in your lower unit it could be any on of the seals. After you fill the lower unit with the vent plug in you should not get oil to run out. If you do you have a bad seal somewhere. I would check the shift rod seal first.

If you drained it good no need to change it right away. After you get it out on the water for a good romp just let it sit in the running position a couple days and bottom drain it. Let the water settle down and quickly drain a small amount out and see if any water is present. If not just top it off in the upper hole and go boating. I have a oil can with gearoil makes it easy to top off. If you get water drain it fully and do a pressure test with no more that 8 psi air pressure. Spray soapy water on the seals and plugs and see where the bubbles are coming from. If you dont know how old the seals are just do a complete reseal and go boating.

Long as it's dry (no water), filled with oil, and not left in the water, you can get away with leaky seals--for a while.

Jeff

Update: All seems good. I ran her hard last weekend....when I checked the LU oil afterwards - it was as blue as it was when I put it in...and no water...so feeling good so far.

Thanks for the feedback