Interchangeability between 7.5 & 6 lower units

I?m curious as to just how interchangable the lower unit (case and all internals) are between the 1956 ? 58 Johnson / Evinrude 7 ?, 1956 ? 64 Johnson / Evinrude 5 ?, and the later 1965 ? 1979 Johnson / Evinrude 6. They look identical. It is a fact that the 5? & 7? shared the same lower unit according to the manual I have. I was just curious if a later, more plentiful and potentially less used up 6 could be a donor for lower unit parts if need be. Thanks in advance (fingers crossed).

Re: Interchangeability between 7.5 & 6 lower units

The newer gearcases are not the same. There is a spring-loaded device in the older ones that acts as a relief mechanism for the drivetrain, in the event that something is hit under water. You'll know which gearcase you have by the shear pin position on the driveshaft. If it is toward the front, next to the back of the gearcase, its the newer configuration, without the recoil unit. If the pin position is at the end of the driveshaft, its the older style gearcase that includes the recoil.

We had a long discussion about this in another thread because I had actually put a 5.5hp gearcase on an early 6hp motor, and didn't realize that there is a difference (I own a couple of later model 6hp Johnsons too), because this mechanism is buried down in the gearcase, under the water pump.


PS: Found the thread I was referring to - its kind of long but will probably tell you everything you want to know.

http://forums.iboats.com/showthread.php?t=232496&highlight=6hp+gearcase

Re: Interchangeability between 7.5 & 6 lower units

There are lots of 7.5 hp lower units around. Also, the 5.5 hp lower is the same, but the prop is different.

Re: Interchangeability between 7.5 & 6 lower units

This is all good info, and I appreciate all your answers and the link to the other thread. It appears that the lower unit on the 1965 6 is the same as the earlier 5.5 & 7.5. Of course the props are different as well, but I was not aware of the difference with the shock absorber and the other changes that were made to support the change in shock absorbtion on the post-'65 6 horse.

It's funny, the old style driveshaft shock absorber looks to me like the early clutch mechanism on the old Johnson TN 5-horse and the first of the 7? Evinrude Fleetwins from 1950-53.

I got the Seahorse 7? as a project to learn on, although it is a runner. I always liked the fifties style and hope that by the time I'm done it will look like new and perform flawlessly.

Re: Interchangeability between 7.5 & 6 lower units

The TN had a shock absorber AND a neutral clutch. Yes, the shock absorbers on the TN and later models were similar but different.