1971 Mercury 40 4hp Lower Unit

[sflynn006]

Hi,

I have a '71 Mercury 40 4 h.p. Thunderbolt ignition. I have a question concerning the lower unit. I'm in the process of changing my gear lube down there and have the old lube drained from the fill and drain screws on the right side (looking from the back) of the lower unit. But I noticed that on the left side of the lower unit there are two holes (approx. 1/8"), the lower one is towards the front of the lower unit on the same vertical height as the top of the propeller. This lower hole has a very slow drip of bubbly fluid (presumably water and oil mixture). Looks identical to what's coming out of the exhaust on the back side under the head of the motor. I was just wondering if that was normal!?!? I hope that made enough sense. Please let me know if more description is needed!


Thanks in advance!

 

[fastjeff]

Water drain holes, so it won't freeze crack.

Jeff

 

[sflynn006]

Water drain holes, so it won't freeze crack.

Thanks Jeff! I was just double checking. After changing my gear lube and running it for an hour and a half last night the motor is running great, but leaking lube on the prop. Guess I will be looking for a prop shaft seal soon.

 

[racerone]

Might be normal on a 2 stroke.------------I recommend a pressure test on that lower unit.-----Shafts were not stainless and tend to rust and damage seals.

 

[sflynn006]

It was quite a bit of lube in and around prop. How do you perform a pressure test on that lower unit? And I was thinking about ordering a complete lower unit seal kit rather than just the prop shaft seal. Does anyone know how hard it is to change out all those seals and O-rings? Any special tools required?

Here's the seal kit I was looking at: http://www.boatpartheadquarters.com...MTZ9_pPSV4MHb4XM9LeAU5h4KpRNxr6E7waAiby8P8HAQ

 

[flyingscott]

Do the smell test gear lube has a distinctive smell. If it's fuel probably normal.

 

[sflynn006]

I cleaned it all up already, but it was grey (same color and viscosity of the old gear lube I drained from the lower unit a few days ago). I also loosened up the bottom screw again to check the fresh lube I just put in and while there was no water that immediately came out, the new lube was already pretty milky.