'73 85 HP interchange parts with '77 85HP?

I need a new rams for the manual tilt on my '77 85 Johnson. Being broke & looking around, I found a complete motor really cheap, but is a '73. Seller says powerhead & middle are good, (rams are good) but lower unit bad. I'm going to pick up tomorrow. Depending on the actual condition of motor, will either my '76 or '77 lower units fit this motor? What years can interchange parts? I asked if it was a red plug motor, he didn't remember.. If not, I'll just hold it for parts..
Thanks in advance! LG17

Re: '73 85 HP interchange parts with '77 85HP?

I'm almost positive the '73 is the last year of the hydroelectric shift. In which case it's got a square crankshaft fitting (not splined) and your lower unit will not fit. Don't know about the ram.

Re: '73 85 HP interchange parts with '77 85HP?

I think that 73 is actually the first year in the 73-77 series of motors and that 72 was the last year of the electric shift models so everything should fit.

Re: '73 85 HP interchange parts with '77 85HP?

The shocks on the 1973 85HP are shock absorbers, while the 1975 and up models have tilt assist cylinders whch compress air as you lower the motor and use that to help raise the motor. The Tilt assist cylinders have to be replaced with shocks if you add the OEM PT&T.

The 1973 85HP is the first in the series of hydro-mechanical gearcases; they are the same as the standard 20" 1977 85HP and 115HP gearcases.

The powerheads are not the same.

The 1973 motors started life with a stator that had a lot of problems and most were replaced with gereen ones with potting material around the coils; look up under the flywheel to see that yours has been updated.

The 1973 motors had an automatic choke feature that was eliminated in later models and was usually disabled by service departments on the earlier motors.

The 1973 motor had a neutral safety switch at the engine that was redundant if you had the standard remote, so that was also removed in later models.

The 1973 model did not have the trailering tongue to support the motor.

So, except for the powerheads and these items, most everything else should swap fairly easily.