Tohatsu lower unit oil leak

[bill2452]

I have a 25 HP 2cycle Tohatsu, guessing it's about 15 yrs old. It leaks oil from the lower unit tattle tale hole that's about 1/8" diameter. I've been told that this is a leaking shift shaft seal. Does anybody know if this info is correct? What's involved in changing this seal? Any help GREATLY appreciated!

Thanks,
Bill

 

[TOHATSU GURU]

Re: Tohatsu lower unit oil leak

You have to pressure test the lower unit to determine where the leak is....Unless it's an obvious leak.

 

[bill2452]

Re: Tohatsu lower unit oil leak

Thanks for the reply Guru. I've disassembled the lower unit, all gears are out now. Can you tell me how the shift shaft assembly comes out? I've removed the screw-in pin on the side of the case. Does that pin hold in the assembly? If it does, it won't budge, but maybe I'm going at it backwards. Does the entire assembly pull out through the top of the case?
Thanks for the help,
Bill

 

[TOHATSU GURU]

Re: Tohatsu lower unit oil leak

Why are you taking the lower unit apart for a leak???

 

[bill2452]

Re: Tohatsu lower unit oil leak

Why are you taking the lower unit apart for a leak???

The drive oil was leaking out of the weep hole in the bottom part of the drive. Looks like the shift shaft is the only place it can come from. Any idea how the shift mechanism comes out? It looks like if I remove the screw-in pin on the side of the case, the entire thing should pull up and out,,,,,,,is this how it comes apart? If this is how it comes out, it's stuck! Didn't want to get too rough with it.
Thanks,
Bill

 

[TOHATSU GURU]

Re: Tohatsu lower unit oil leak

The screw holds the shift rod in place, so once you remove it the only thing holding the the rod in is friction. Oil can come from the driveshaft seal so you really should have pressure tested the lower unit before you did anything. You now need to replace all of the gaskets and seals in the lower unit.

 

[bill2452]

Re: Tohatsu lower unit oil leak

Thanks Guru. That gearcase had lots of crud inside so I'm not too disappointed that I need to replace all the seals. With my luck, I'd have replaced the obvious leaker, reassembled, and next week have a different one start leaking.
Thanks,
Bill

 

[bill2452]

Re: Tohatsu lower unit oil leak

The shift shaft is out, thanks for all the help Guru! I'm really glad I took the whole thing apart, It was really cruddy inside, and the void above the shift shaft was packed full of greasy stuff. The pressure washer worked wonders.
Guess I'd better get a seal kit coming!
Bill

 

[stoked1]

Re: Tohatsu lower unit oil leak

The screw holds the shift rod in place, so once you remove it the only thing holding the the rod in is friction. Oil can come from the driveshaft seal so you really should have pressure tested the lower unit before you did anything. You now need to replace all of the gaskets and seals in the lower unit.

Hi there and thanks for the info I've gleaned from both of you already - I've just bought a boat with a 70 HP Tohatsu, 1988 M70A2 motor, which this morning (after a couple of weeks and 4 trips) had a new leak of gear oil dripping from the small hole just forward of the water intake on the lower leg (just above the propeller) I guess this hole is supposed to be an indicator of oil leaks, just wondering if it indicates any seal in particular?

The mechanics that put a new impeller in just before I picked the boat up had to heat the bolts holding the impeller housing to get them off, and may have cooked the seal closest.

Is there any trick to removing the lower unit?

Thanks for any help.

 

[pvanv]

Re: Tohatsu lower unit oil leak

First a little netiquette... You are replying to a 2-1/2 year old post about a different model motor. Probably better to create a new thread. That aside...

You are seeing fluid coming out of a drain hole. the hole is there to allow sea water to drain out, so it doesn't stay inside and corrode/freeze. The fluid could be either gear oil, or it could be unburned fuel/oil residue. Is it nearly clear, or is it nearly black? If the latter, probably just fuel residue. If the former, you should consider re-sealing the LU. The shift rod bushing o-rings are often overlooked, and will eventually (after 22 years) weep. You could also need a driveshaft seal. On a motor of that vintage, I would probably change all the LU seals for insurance, as long as the prop shaft housing isn't corroded in place -- if it is, then it would be best to leave sleeping dogs lie for now, as you can damage the prop shaft housing by attempting to remove it.

The only way to know for sure is to pressure test the LU and see which seal(s) are leaking. When you drain the LU lube, does it come out clear or milky? If the latter, you have water inside, and do need to replace some seals.

Grab a factory service manual, available from any dealer, and that will explain how to drop the LU. Get a new set of seals (or at least the driveshaft and shift rod items), and you're ready to go.