1968 Merc 200 20 HP Lower Unit Oil Leak

[JGra]

I have an old Merc 200 that I am getting running after sitting for about 15 years. I have made a lot of progress with it so far. I rebuilt the carb and fuel pump. I replaced all the old rotted wire and Have it running really well. The water pump seems to be pumping but I have a new impeller and gasket kit on the way. From what I have read people seem to push the water pump replacement. My question is on the foot. Just above where the lower and upper case come together there is a small tiny 1/8 inch hole that looks like is supposed to be there. There is fresh lower unit oil leaking out of this hole. I just changed the fluid in the foot and it looks fresh. I have seen posts on this and they say unburned oil can come out of this hole but this is fresh lower unit oil. I was also reading where it could be the shift rod seals. The shift rod looks like it runs right next to this hole. I will have the lower half off to do the water pump and am wondering how much of a job it is to do the shift rod seals. Any help would be help full. Thanks

 

[7920hpMercury]

Re: 1968 Merc 200 20 HP Lower Unit Oil Leak

Great motors and glad to hear you got it running!

This little hole is a water drain hole for the forward top of the lower unit. When you drop the lower unit, look directly above the hole on the inside of the lower unit and you will see the shift shaft seal and a small locking square headed nut. Next to the shift shaft seal is a vertical opening in the casting that connects to this little hole. Most of these holes are plugged up with river silt and need to dug out and flushed to drain properly. If you have oil coming out, I would guess that is residual oil from the exhaust.

These are great motors but if original, do have carbon steel drive shafts and carbon steel shift shafts (would have to check on when they went to ss on shift shaft). Anyway, as carbon steel rusts, these drive shafts can leak (sooner). In 75 they went to a split ss/carbon steel drive shaft and all stainless steel in 76. Grubbs makes a ss sleeve just specifically for a fix for this or you can install a ss shaft. So, if the lower unit is not leaking, I would just run it and keep an eye on it. If you decide to replace seals, I would reseal the whole lower unit. Get a Mercury or Seloc service manual and you need to make or buy a cover nut tool. I think you should replace the water pump every couple of years on these motors.

Good luck and a great red stripe!

 

[JGra]

Re: 1968 Merc 200 20 HP Lower Unit Oil Leak

Thanks for the reply. I dont think its residual oil from the exhaust though. It looks, feels and smell like fresh lower unit oil. I have 2 o rings and a seal ordered to try and repair this when I drop it for the water pump replacement. Wish me luck. Not a bad little motor for being 41 years old.