Mercury Lower Unit Threads

[Jaynen]

I got a 1974 Mercury 500 50hp and I took apart the lower unit cuz reverse didnt work. I am in the process of hopefully getting it back together. I just have to tighten down the bearing carrier and there are 2 sets of threads there. A smaller diameter hole with threads closer to the gears, and an outter set of threads with a slightly larger diamter. The threads on the inner diameter look pretty messed up, while the threads on the outer diamter look okay. I had to break the cover nut when I took it apart, so I got a new one ordered. Will the cover nut go on the inner or outter threads? If it wont thread on is it okay to weld the carrier on instead. Anyone else have troubles with these threads?

 

[Faztbullet]

Re: Mercury Lower Unit Threads

Will the cover nut go on the inner or outter threads?

Inner...

If it wont thread on is it okay to weld the carrier on instead. Anyone else have troubles with these threads?

No as you cannot compress o-ring for sealing and also get correct shimming on reverse gear.

When you get the new cover nut it may be the plastic one. If so threads need to be pretty straight or it will strip. If you get the aluminum one just cut you some grooves straight across the threads to make it a chasing die and work slowly to clean them up...

 

[Jaynen]

Re: Mercury Lower Unit Threads

Would the mercury dealer sell the tool to install the ring? Or can something else work or be bought somewhere else?

 

[Chinewalker]

Re: Mercury Lower Unit Threads

Depending on the level of helpfulness at your local Merc shop, bring the unit in - retainer ready to install - around coffee time with a box of good donuts and asking to borrow the tool might work...

 

[Moody Blue]

Re: Mercury Lower Unit Threads

If you get the aluminum one just cut you some grooves straight across the threads to make it a chasing die and work slowly to clean them up...

I'll have to remember that one. Nice trick.