50-55hp lower unit swap, 1972 to 1977

[scott_maier]

Hello,

Does anyone know if a 1972 50hp lower unit will fit a 1977 55hp? (Assuming the drive-shafts are the same length).

thanks in advance,

 

[hidef]

Re: 50-55hp lower unit swap, 1972 to 1977

I don't believe you can make it work. The electric start 50s in 72 had the hydro-electric shift which is differently not compatible. The rope start 50 did use a mechanical shift but the part numbers are all different from the 77 gear case. The only way to tell for sure would be to try bolting it on a rope start 72 gear case to the 1977 55.

 

[Daviet]

Re: 50-55hp lower unit swap, 1972 to 1977

I think there is a conversion chart in the "Top Secret File" that might help youout.

 

[scott_maier]

Re: 50-55hp lower unit swap, 1972 to 1977

I don't believe you can make it work. The electric start 50s in 72 had the hydro-electric shift which is differently not compatible. The rope start 50 did use a mechanical shift but the part numbers are all different from the 77 gear case. The only way to tell for sure would be to try bolting it on a rope start 72 gear case to the 1977 55.

Okay thanks. I won't mess with it then. Got a local guy parting the 72 out and I thought I might be able to use the foot.

 

[ronsealdeath]

Re: 50-55hp lower unit swap, 1972 to 1977

Funnily enough I had a 72 50hp as a part motor for my 77 55hp. The gearcase on the 72 was an electric shift so definitely not compatible but also was a slightly different size. Not sure if it would even physically fit? You can use the powerpack, solenoids and a few other bits though.

 

[scott_maier]

Re: 50-55hp lower unit swap, 1972 to 1977

Just got a reply from the seller and it is an electric shift, but would probably make a good parts motor. Decisions, decisions.

 

[scott_maier]

Re: 50-55hp lower unit swap, 1972 to 1977

I think there is a conversion chart in the "Top Secret File" that might help youout.

Where is the "top secret file" ?

 

[hidef]

Re: 50-55hp lower unit swap, 1972 to 1977

If you had a 72 electric shift motor. You will find very few of the parts on that 72 are compatible with your 77.

 

[Daviet]

Re: 50-55hp lower unit swap, 1972 to 1977

Lots of great information in there.
http://forums.iboats.com/showthread.php?t=299680