lower unit seals

I want to replace the seals in lower unit on my 1977 mercury 850 85 horse. Water is getting into the lower unit, is there a kit or any special tools anyone recommends? I hear either the shift lever oil seals or the driveshaft seal needs a special tool.

Re: lower unit seals

Without performing a pressure AND vacuum test, I would start with the cheapest and simple approaches.

Water has 4 ways it can get into the LU.

1) prop shaft seals - difficult to replace, specialized tools required (not for the faint of heart)
2) fill and drain screw gaskets - cheap and easiest to replace. Takes 5 minutes and costs $2.
3) shift shaft seal - specialized tool required (tool can be made), seal (bushing assy) is cheap. Lower unit must be removed.
4) waterpump driveshaft seals - basic tools required, seals are cheap, lower unit must be removed. Good time to replace waterpump impeller.

Seals are purchased separately and are not (that I have found) available as a kit.

Re: lower unit seals

You can get the seal kit thru iBoats part number 18-2653 and it comes with the complete shift shaft bushing and seal. The early model motors used a mild steel shaft and are bad about cutting grooves in shaft below water pump base. This can be repaired with a speedysleeve...

Re: lower unit seals

I recommend you change the driveshaft seals and fill and drain gaskets first, and recheck. Those have always been the ones that would leak, in my experience.

Re: lower unit seals

Faztbullet said:

You can get the seal kit thru iBoats part number 18-2653 and it comes with the complete shift shaft bushing and seal. The early model motors used a mild steel shaft and are bad about cutting grooves in shaft below water pump base. This can be repaired with a speedysleeve...

Click to expand...

That's good info Faztbullet. I inquired here last year about the same thing and was told that one wasn't available. Should have done my homework I guess. What model years would that kit cover?

Re: lower unit seals

Its a universal kit, you will have a lot of o-ring and seals not used..
Fits inline 4 & 6 cylinder 76 & up 75-150 hp
Fits early style cam shift V-6
Fits Xr4 small gear case pre 88

Re: lower unit seals

Faztbullet said:

Its a universal kit, you will have a lot of o-ring and seals not used..
Fits inline 4 & 6 cylinder 76 & up 75-150 hp
Fits early style cam shift V-6
Fits Xr4 small gear case pre 88

Click to expand...

Maybe that's why. I have a 1971 vintage Merc 800 unit. Ended up buying all the seals separately.