Johnson 90hp Water in Lower Unit

Hey guys,

I just picked up a 17' Mako with a 1997 Johnson 90hp. Its a V4 2-cycle engine. Anyway- the guy I got it from hadn't ran it in a few years. I replaced the starter and it fired right up, however it didn't pump much water, and there was alot of oil coming out from the prop area. I checked the lower unit oil and it was slightly milky. So I took off the lower unit to replace the water pump and upper driveshaft seals.

Brought the lower unit over to a shop to get pressure tested, and sure enough the upper seal was leaking. They recommended I replace the 1-piece seal, with the older style 2-piece seal (used on early 90's and earlier v4's), so he sold me the parts and I cleaned everything up and replaced the seals and put in a complete water pump kit. I also cleaned out the thermostat housing and thermostats which where caked with sand. -

Then I refilled the lower unit oil, put the muffs on and fired her up. Much more water was pumping now, and I thought I was in the clear- however alot of oil still coming from the prop area. From searching around I just figured it was unburnt 2-stroke oil (some of it was dark and thick, and some was a more milky consistency) However, I pulled the drain plug on the lower unit and out came milky oil again. So after running on the muffs for 10 minutes or so the oil was milky again.

Now I'm thinking its the bottom prop shaft seal- but since I had the motor just on muffs, was it possible for water to get in that seal? (since it wasn't submerged) Because if not- I figure maybe something up top is leaking again and I'll need to pull the unit off again to get it pressure tested again. (Maybe the shift seal? or the something with the new seals I just pressed in the driveshaft bearing housing?)

Thanks in advance for any help!
-Shane

Re: Johnson 90hp Water in Lower Unit

You might take a look at the condition of the drive shaft in the region where it goes through the upper seal. Excessive wear, surface irregularities or debris might prevent an effective seal from occurring.

Re: Johnson 90hp Water in Lower Unit

Thanks,
Yes I was told to look for this, the parts guy showed me some driveshafts that had rings worn around in the spot where the seals were....however my driveshaft looked perfect- not even a bump/ridge in that area.

Re: Johnson 90hp Water in Lower Unit

Shane, the upper gearcase seal and bearing might be in a carrier housing that seals to the lower unit by means of a large o-ring around the outside of the carrier housing. O-rings that have been installed for a while can suffer from "compression set" which basically means they go flat on the side becuase they loose some of their elasticity and therefore don't seal. You might try looking in this area at everything - the o-ring, the o-ring groove, and the o-ring seating area. Both the groove and seating area must be clean and smooth. Check for corrosion and well as the usual build up debris in these areas. You also might check for other restrictions in the cooling water passages which might be causing unusually high back pressure. Good luck.