Is the drive shaft boot necessary?

hello- I have a 1989 force 35 model #357F9A - this motor is in mint condition, not a scratch, super clean, always maintained, starts right up, and runs like a top...

For the first time I dropped the lower unit and attempted to change the impeller. Everything seemed to go smooth. I had to tap the seal retainer off of the top of the drive shaft to remove it so that I could slide the old impeller off. I noticed that the driveshaft spline seal was a bit worn, it looks like a boot that hold that keeps the grease on the upper drive shaft splines. Is this rubber boot necessary to re-install if this motor is only run in fresh water? I had a local mechanic tell me that the boot is needed mainly for salt water use. Thanks

Re: Is the drive shaft boot necessary?

Lots of motors are missing that boot.

Shouldn't be a problem.

Re: Is the drive shaft boot necessary?

It's to keep the grease on the splines. Not needed.Jerry

Re: Is the drive shaft boot necessary?

With that being said...the drive boot...as Jerry pointed out...is to keep the splines greased...Since the drive shaft is not made of stainless steel, moisture from condensation can cause the drive shaft splines to rust. Since the lower crankshaft bearings inner race is also not made of stainless steel it can also rust...basically fusing the drive shaft and inner race together. This can make it a major pain in the..."booty", pun intended, to remove the lower unit next time the need or want arises should the splines not be greased sufficiently.

Re: Is the drive shaft boot necessary?

Well, Matt, You almost have it correct! The drive shaft IS stainless but the crank and its splines are hardened steel which will rust. The lower seal protects the bearing (which is above it) so there is little worry there--If that seal goes bad, the engine will not run well.

However, the drive shaft should be lightly greased with anti-seize compound--lightly, to prevent pre-loading it when assembled into the crankshaft. The boot while helping to keep anti-seize in, primarily helps keep moisture out of the crank splines, preventing them from rusting and fusing to the drive shaft. On small engines like this that are run and usually trailered, the latent heat after shut-down will dry out any moisture up near the crank and even on humid days, moist air will not work its way back up to this area. So no, the boot is not absolutely necessary, but is sure is good insurance and I would install one given the choice. Remember, Force engines are entry level price point engines. The manufacturer is not going to install anything not necessary for longevity or operation.