Lower unit problems......

[bizzy2]

I have a 1974 Mercury Thunderbolt 20hp with lower unit damage. The threads are broken and smashed together and will not allow the BEARING CARRIER ASSEMBLY part to screw in before the prop is put on. It is the threads that are on the inside of the lower part of the gear casing. Any ideas on where to find a reasonably priced lower unit or how to fix the one I have?

 

[Faztbullet]

Re: Lower unit problems......

Take a NEW cover nut and cut some slots across the thread to make a chasing die tostraighten threads. Use some motor oil as lube as when it stops from buildup, back it up and clean threads and restart..

 

[bizzy2]

Re: Lower unit problems......

The cover nut threads are okay, its the threads that face in and are about 2.5" in diameter. The BEARING CARRIER ASSEMBLY is the part that has threads on the outside of it and is unable to screw into the lower unit at this time.

 

[1979checkmate]

Re: Lower unit problems......

Yes, Faztbullet was correct.

He wants you to take a new cover nut, and cut channels across the threads and slowly turn in the cover nut, (it will act just like a big tap, have you ever used one of these? This should straighten the threads in the housing back out. Honestly, this is absolutely no disrespect against you, but if you dont feel confident doing this or are not sure what we are talking about, take it to a shop. It isnt worth screwing the lower up worse.

 

[Faztbullet]

Re: Lower unit problems......

The only 20 hp I know of that uses a threaded carrier is the mid 80's and up models,the 1974 uses a slide in carrier held in place with a cover nut. Same principle applys just use carrier with slots cut into threads.