1970 Mercury Thunderbolt 500 50 HP, shift shaft

C

cory49

Cadet
Joined
Sep 2, 2008
Messages
6
Hello,

I have a 1970 Mercury Thunderbolt 500 50HP (Serial #2742248) and noticed i lost reverse. I removed the lower unit, and to my surprise the shift shaft was broken right at the spline. I am unsure of the names of all the parts, but I will take pictures tomorrow to help explain myself. Question is where can I buy this shaft? It seems it goes straight up, right underneath the engine. If this part is available, how big of a job is it to change? Seems like engine removal is needed to do this?

Anyways, if you do not understand what fully mean, I'll snap some pictures tomorrow. Thanks,
Cory
 
AMD Rules

AMD Rules

Lieutenant Commander
Joined
Sep 23, 2004
Messages
1,707
Re: 1970 Mercury Thunderbolt 500 50 HP, shift shaft

Your description suggests you broke the upper shift shaft, not the lower shift shaft. To replace it without removing the power head could be quite a challenge.

Easiest route to take is to remove the power head from the mid-section. You can leave the mid-section on the boat.

You'll need to find a place that sells old motor parts. Depending on where you live that could be challenging. Shift shafts are no longer available new. I'm not confident you could weld repair it, maybe.

New shift shaft and a new power head base gasket and you're back on the water. Its not a lot of money, but will be time consuming.
 
F

Fox1011

Cadet
Joined
Jun 8, 2008
Messages
15
Re: 1970 Mercury Thunderbolt 500 50 HP, shift shaft

cory49 said:
Hello,

I have a 1970 Mercury Thunderbolt 500 50HP (Serial #2742248) and noticed i lost reverse. I removed the lower unit, and to my surprise the shift shaft was broken right at the spline. I am unsure of the names of all the parts, but I will take pictures tomorrow to help explain myself. Question is where can I buy this shaft? It seems it goes straight up, right underneath the engine. If this part is available, how big of a job is it to change? Seems like engine removal is needed to do this?

Anyways, if you do not understand what fully mean, I'll snap some pictures tomorrow. Thanks,
Cory
Click to expand...

I may be aprting out a 1969 500 Merc that has a great lower unit. Right now mine is needing a Solenoid for the starter. There may be another issue too and that is the one that may cause me to just part it out. If the shift shaft for a 1969 serial number 2629343 will fit I might have the answer for your problem.
Ed ag869@aol.com
 
C

cory49

Cadet
Joined
Sep 2, 2008
Messages
6
Re: 1970 Mercury Thunderbolt 500 50 HP, shift shaft

AMDRules, yes I broke the upper shift shaft. It was all rusted completely right at the bottom, I was suprised it lasted that long.

Mikesri14, thats the part I'm looking for! I will be talking with the Mercury Mechanic who specializes in the older stuff, who may have one here locally.

Now, the question of replacing the part. Where the heck do I start? I need a manual, is there anything available for download online? How are those Clymer Manuals I see at local parts stores?

I appreciate the help so far, thank you,
Cory
 
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