Re: Chrysler/West Bend/etc recoil starter pinions

[amuller]

OK, I’ve been piddling around with this and have some thoughts to share:

The pinion type recoil starter used by OMC on 5-8 hp units is so similar that it must be licensed or a direct copy. Could be that the OMC 13 tooth pinions could be used on Chrysler, etc, motors. The ID (bore) seems larger but the spindle is not larger. A very loose fit seems part of the design.

Patent US 2938511 A, filed 1955, published 1960, gives a good description of the thinking behind the original design. https://www.google.com/patents/US2938511

Appears to me that when the change was made from the 11 tooth pinion to the 13 tooth pinion (when?), the pitch of the teeth was not changed, nor was the flywheel changed. Rather, the center-to-center distance of the starter spindle to the crank was increased by about 0.141" to make room for a more robust pinion hub, and the two teeth were added to maintain the same pitch while increasing the diameter. If this is so–I haven’t yet examined enough machines to confirm it–it should be possible to use the 13 tooth pinion on 11 tooth machines by shimming the starter spindle out about 9/64in (0.141).

On the 11 tooth motors I’ve looked at (a 1957 and a 1961) the starter spindle brackets are integral with the intake manifold, so moving the spindle outward would require 2 crescent shaped shims, plus 4 flat shims under the bearing caps. These crescent shaped shims would be easy enough to make on a lathe, but since all the loads are outward–away from the crank–epoxy putty might serve as well.

It appears there are at least two 13 tooth pinions available from Mercury:

F525674 (etc) is usually black and has a flange extending out from the major diameter of the pinion teeth. this one seems to have been used on smaller motors. (https://www.amazon.com/F525674-Chrysler … B015NJ6VLO)

803624 (etc) is usually white and lacks the flange. (http://www.boatsportandtackle.com/start … and-15-hp/)

I have no feel for which of these would be most desirable. I am sure there are people here who know a lot more than I do about this.

Any feedback appreciated.