Advice on lower unit seals for 1999 40hp 2-stroke

[GavinHeyes]

Hi all. I just drained the oil from the lower units of my beloved 40 yammies and out came condensed milk with a rotten egg odour! Clearly there is a leak somewhere. I would like to order spares to reseal the unit and would appreciate any advice on which seals/gaskets would be necessary to replace.

 

[robert graham]

Re: Advice on lower unit seals for 1999 40hp 2-stroke

It could have leaked at the drain/fill plug washers, the prop shaft seal, the drive shaft seal or the shifter shaft seal. Check your drain/fill plug washers first, just to eliminate those as the culprits. Then remove the prop and inspect the prop shaft seals for fishing line or warn or damaged seals there(the most likely place for a leak). If those are good then check the drive shaft and shifter shaft seals on top of the motor foot(after foot removal). If the bad seals are not visible and obvious to the eye, then you may need to do a lower unit pressure test to locate the leak(like checking a car radiator for a leak with a small hand-held pump). Good Luck!

 

[GavinHeyes]

Re: Advice on lower unit seals for 1999 40hp 2-stroke

Thanks you very much for the concise answer. I will get onto it ASAP!

 

[robert graham]

Re: Advice on lower unit seals for 1999 40hp 2-stroke

If it was saltwater that leaked into your lower unit, it would be a good idea to flush/clean the unit to remove corrosion/salt deposits as soon as possible. I would pump the lower unit full of fresh oil, crank up the motor, shift through the gears(with motor running if possible) to circulate the oil, and then drain it. Saltwater can wreak havok on gears and bearings! I've had lower unit seals leak saltwater and turns the lower unit bearings and gears black with corrosion! Good Luck!

 

[GavinHeyes]

Re: Advice on lower unit seals for 1999 40hp 2-stroke

Damn! Put new oil in and ran in fwd and rvrse - the right motor makes an expensive sounding rattle/clanging noise down near the gearbox. Will have to take that off and have a look on Sunday.