Tohatsu lower unit oil leak

toby1

Cadet
Joined
Oct 8, 2007
Messages
8
I have a mid 80's tohatsu 8 hp outboard with a pretty major lower unit oil leak. When I drained the oil last Fall, I had primarily water come out. I realize I may have some damage / corrosion as a result, but am trying to fix the leak anyway.

After pressure testing, it appears that there is a bad leak around where the shift linkage enters the lower unit. I don't see much about this part in the shop manual, and was wondering if anyone had any advice. I assume there are some o rings or some kind of seal in there, but am not sure.

Thanks in advance for any advice.

Dan T
 

toby1

Cadet
Joined
Oct 8, 2007
Messages
8
Re: Tohatsu lower unit oil leak

After further reseaerch, I am wondering if there is no seal at the shift linkage entrance, but it is leaking there because of a failure at the seal, and /or O-ring at the base of the lower water pump case.
 

pvanv

Admiral
Joined
Apr 20, 2008
Messages
6,500
Re: Tohatsu lower unit oil leak

There are shaft seals for the driveshaft and the propshaft. There is also an o-ring for the propshaft "spool" housing. As for the water pump housing, that uses a flat paper-type gasket.

Look at TG's website, and pull up the oldest (1992) NS8B parts catalog he has online at http://www.internetoutboards.com/Pa...oke/Parts Catalog NS8B (1992) - (M279-B).pdf

Under the SHIFT section, you will see the typical Tohatsu shift rod bushing, held in place by a cap-screw-mounted metal retainer. That bushing has both an internal o-ring that seals the bushing to the shift rod, and and an external o-ring that seals to the LU case. These o-rings are often overlooked. The internal ring has to cope with the sliding of the shift rod, and will eventually fail.

Seals are available at any Tohatsu/Nissan dealer. I would suggest that while you have the LU down, it would be prudent to do the water pump kit as well as all seals. Inspect the gears and bearings for corrosion (you may get lucky here, since you drained the LU last fall), and then reassemble. HTH.
 
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