1992 90HP Johnson - Water in lower unit

[Striper500]

I purchased this motor last year and ran it for approximately 12 trips on a newly filled lower unit. I went to change the gear oil this year, and it was milky in color. It appears as though I am taking water in, not leaking oil out. I say this, because when I pulled the top plug the gear case was full. Any ideas on what would be the most likely cause of this ? from what I understand, the seal under the water pump is one of the more common to go bad. However, I don't want to go through the trouble of changing it without being for certain. I once watched a mechanic do a pressure and vacuum test on a lower unit to try and determine the cause of the leak. Is there any way that I can perform this type of test w/o bringing it to a dealer ? Any thoughts or ideas would be greatly appreciated.

 

[OBJ]

Re: 1992 90HP Johnson - Water in lower unit

Hey Striper.....<br /><br />When was the last time you changed the drain and vent plug seal oring? Have you checked behind the props thrust washer for any fishing line?<br /><br />You can make a pressure tester out of a bycycle pump. Just adapt a fitting to the end of the hose that fits the drain/vent plug threads. Those pumps you can buy to fill lower units from a quart or gallon jug are fitted with an adaptor that would work. Just dunk the lower unit into a garbage can full of water and start adding pressure to the lower unit....(drain lower unit first of gear lube... ) and watch for bubbles. All ya' need is 10 to 15psi.<br /><br />I got a vac tester used for auto A/C checks. Got a gauge already on it. Again, just put the fitting on the end of the vacuum hose.

 

[Striper500]

Re: 1992 90HP Johnson - Water in lower unit

Yes, I have always changed the nylon washers everytime I changed the gear oil...so I assume it is not those. no fishing line either. I think it sounds like I will most likely need a vac tester.

 

[OBJ]

Re: 1992 90HP Johnson - Water in lower unit

Finding a leak that sucks in is a little harder than one that blows out. Usually it's either the prop shaft seal or the driveshaft seal. But just remember...when in doubt...replace them all.

 

[ob]

Re: 1992 90HP Johnson - Water in lower unit

If you do end up dropping the lower unit for seal replacenment,don't forget the shift rod seal as a potential leak source.