74' Thunderbolt with lower unit troubles...........

[bizzy2]

I have a 1974 Mercury Thunderbolt (20hp) 200 that had a piece break in the lower unit. I can get a replacement part, but I am having troubles getting the broken piece out of the lower unit. The threads are also a bit beat up but my main problem is getting the broken piece out. Thanks. And one more quick question, is the prop suppose to be able to rotate with a hand, because mine won't, or is that normal?

 

[carholme]

Re: 74' Thunderbolt with lower unit troubles...........

bizzy2;

First, what is the serial number and model number of the engine, if you have them?

As far as the prop turning or not will depend on what gear you have it in.

Is this lower unit removed from the engine or still installed as it is difficult to tell from the photos?

What caused this damage as it looks more man made than from operations?

Gerry

 

[James Jacksonville fla]

Re: 74' Thunderbolt with lower unit troubles...........

thier is a retainer ring that you removed??? that piece of aluminum used to have a ring around the top aswell. at the bottom thier is an o-ring that holds all the foot oil inside. it should just pull out??? i replaced that same seal i cant remember if it was threaded at the top but i do know thier are no threads at the bottom. it uses the pressure of the retainer bolt the one you probally had to break off? use a pair of pliers and grip it in the middle and with a twisting pulling motion it might come out if not? you could break it out but you risk damaging the shaft good luck!

 

[merc850]

Re: 74' Thunderbolt with lower unit troubles...........

First you'll have to clean up the threads in the housing(a dental/Oring pick might do it), then, clamp the prop shaft between 2 blocks of wood horizontally in a vise and use a rubber mallet to tap on the housing and the shaft and carrier will come out. Be careful that you don't drop the housing when it separates, go slowly; you can put oil around the carrier to help it slip out.
The bearing carrier is scrap you'll have to buy a new one.

 

[carholme]

Re: 74' Thunderbolt with lower unit troubles...........

You will never clean up those threads with a dental pick. Here is a link to previous a previous post by bizzy where Faztbullet describes the same kind of homemade thread chaser that I use:

http://forums.iboats.com/showthread.php?t=456319&highlight=bearing+carrier+cover+nut

Gerry

 

[bizzy2]

Re: 74' Thunderbolt with lower unit troubles...........

The serial # 4020493 and yes I have removed a few pieces but im not sure what the names of them are. I put the broken pieces back together so I could better tell what the part used to look like but I then noticed that there are actually 2 broken pieces. I will post a picture on here tonight of what they looked like. I do believe that I understand how to deal with the threads but I still haven't gotten the broken part out. I sprayed some WD-40 on it and still am not able to move it around and I am a little afraid of forcing it too much because I don't want to damage any other parts. Thanks for all of the help and comments so far!

 

[carholme]

Re: 74' Thunderbolt with lower unit troubles...........

Deleted

 

[bizzy2]

Re: 74' Thunderbolt with lower unit troubles...........

I think you may have searched for the wrong motor..... My engine is a 1974 merc 200 (20 hp). Here is a link to the lower gear housing assembly if that helps any:

http://www.crowleymarine.com/mercury-outboard/parts/464_160.cfm

 

[carholme]

Re: 74' Thunderbolt with lower unit troubles...........

bizzy;

My apologies, I am working on a 500 at the moment and age/alzheimers seems to be playing a part.

I'll see if I can delete that info.

Gerry

 

[Moody Blue]

Re: 74' Thunderbolt with lower unit troubles...........

The bearing carrier will not come out willingly. I made up a nut "adapter" for my 5 Ib slide hammer, and bolted it to the propshaft. Took a good amount of pounding before I got it to move. Mine had been in there since 1971.

Don't try to twist the bearing carrier. It is captured with a small dowel pin to prevent it from rotating in the housing. It slides straight out.

Did you manage to get the retainer ring out in one piece? If so, what is the condition of the threads on it? Looking at the photos, I would doubt you will be able to salvage that housing. The threads look nearly destroyed and the carrier nut has to be torqued to something like 250 ft/Ib. Not sure what is left of the threads will be able to hold that.

 

[bizzy2]

Re: 74' Thunderbolt with lower unit troubles...........

Here are a few pictures of the parts that I have already removed. Moody Blue or anyone else, if the threads are too far gone then instead of getting a new housing would i just be able to tack weld the part in since I don't plan on removing it again? And does anyone know what the bearing carrier does? Does it just help keep the prop steady when its in gear? Thanks again for everyones help!

 

[merc850]

Re: 74' Thunderbolt with lower unit troubles...........

Here's a lower unit diagram as you can see the bearing carrier holds the reverse gear and seals off the unit.

 

[bizzy2]

Re: 74' Thunderbolt with lower unit troubles...........

would it then be possible to weld the bearing carrier into the housing if the threads are too far gone?