I have a 70's johnson 15hp tiller motor that I use on my duck boat. I ran aground a little on saturday and when I pulled the boat out of the water I was leaking lower unit fluid out of the prop. Anyone know how I can fix this or where to begin?
Are you sure it was lower unit fluid? Was it black? I used to have a 80's 25 Johnson, would drip unburned oil from the prop sometimes if I did a lot of idleing especially. Just my 2cts. If it was black and it's just unburned oil, it's not a problem. R/Chip.
I did some research this morning. I think it's an 83 johnson. Yes, it is a milky tan substance and I filled it and ran it with ears and it began pour out of the prop. I tried to drop the lower unit this morning to get a look but I can't get it off. I unscrewed the 6 screws that appeared to be holding it together. I have no idea what i'm doing but I sure want to be duck hunting this weekend.
There is also sometimes a bolt under the zinc tab just above the prop. It sounds like the prop shaft seal is leaking. It can sometimes be replaced without removing the foot from the engine, but if you have never done this before, you can do more damage than good trying to remove the old seal.
you need to remove 7 bolts to remove the lower unit on that motor, 6 on the outside & 1 on the shift rod knuckle that will only be visible after you remove the 6 outside bolts & lower the unit about 1/2 inch, there is no trim tab on that motor, there are lower unit seal kits available for that motor for about $30, it includes all the seals needed to reseal the lower unit,,not a hard job if you are mechanically inclined & have the time.
before you go dissambling anything , I would recomend that you check the cheap & easy things first,, pull the prop & look for fishing line around the propshaft behind the prop, fishing line in the propshaft seal will destroy the seal eventually, sometimes you can cure the leak by just removing the line, also check the filler plug nylon washers. if they have been in there & reused for many years they are often deteriorated & unserviceable or leaking.
Running aground shouldn't have caused any leaking, unless you cracked the LU. I would inspect the housing very carefully. The factory procedure for finding LU leaks is to pressure and vacuum test it, typically no more than 15 psig air pressure with the LU drained of all gear oil first. You could save some messing around time by doing likewise or having a dealer do it. They shouldn't charge very much, since it doesn't take long to do.
Theoretically possible to bend prop shaft and destroy a seal, but I wouldn't expect an immediate, obvious leak in that situation. Main reason for posting is to suggest that if you are moderately skilled but tear down lower units regularly, take photos of everything as you take it apart. Makes it a lot esier to see where the extra parts go when you reassemble. Especially shims and washers.