Lower unit swap (1974, 70hp)

[NCK1500]

I've got a bad lower unit on my 1974 70hp johnson(model# 70ESL74M, serial# J4065710). So far through my searching the only other lower units I have come up with that will work are the 1973-1975 hydromechanical ones off 70hp's. I know there have got to be some others that will work. I would really appreciate any help coming up with what lower units will fit this motor. thanks

 

[OBJ]

Re: Lower unit swap (1974, 70hp)

Welcome NCK1500!<br /><br />You might want to stay within those years. The problem being during those years you mentioned, the throw of the shift rod is opposite of later years. Meaning if you stick a 76' lower unit on the engine and shift to forward.....you'd go into reverse.<br /><br />I believe lower units from 65 horse to 85 horse during those years would fit your engine.....maybe Dhadley can throw some more into this.....he know's that OLD stuff real good.....

 

[Chinewalker]

Re: Lower unit swap (1974, 70hp)

V4 lower units will not work - gotta be from a 3-cylinder. And it has to be a hydromechanical unit, used on the '73 65hp, and '74-'76 70 hp...<br />- Scott

 

[NCK1500]

Re: Lower unit swap (1974, 70hp)

thanks for the info.

 

[Dhadley]

Re: Lower unit swap (1974, 70hp)

The 76 & newer will work. You'll just need the shift linkage fron the powerhead. A very simple swap. The 76 & up shift backwards from the 73-75 units. <br /><br />Any 3 cylinder gearcase from 73 & newer should work as long as it's the 4 spline driveshaft. There is a late model 3 cyl gearcsae that uses a driveshaft with many small splines. That wont fit in your crank. Just look for the 4 spline driveshaft.

 

[Chinewalker]

Re: Lower unit swap (1974, 70hp)

To further DHadley's notes - the fine splined lower units can work, also, if you swap in the driveshaft of an earlier unit with the 4-splines, in addition to swapping out the shift bellcrank lever. I know the driveshaft from a '77 or newer will swap into the '86 or newer, but I'm not sure if a '76 & prior shaft will work... It may, but I don't know for a fact.<br />- Scott