Johnson CD & RD Crank taper question

[RICHARD A. WHITE]

From my limited experience of making the timing tools, most key ways are parallel to the taper, except for the 1962 and up with the large taper.

For example:

28 hp thru 40 hp 1962 and up

1962-1973 28,33,40 ho motors
And the following 35 hp 1976 and 40 hp 1974 thru 1976

The above mentioned the key is parallel with the crank centerline

The others:

22hp thru 40 hp thru 1961 with small crank shaft (including Gale 25 hp thru 1963)

1951-1961 22, 25, 30, 35, 40 hp motors

ALL YEARS 22-25 hp Gale motors

3 hp and 4 hp

1952-1976 3 and 4 hp motors

1981-1986 4 hp motors
5 hp thru 20 hp (including the 22 cubic inch 25 hp)

1951-1976 5, 5.5 and 6 hp motors

1951-1958 7.5 hp motors

1964-1973 9.5 hp motors

1951-1963 10 hp motors

1951 and up 12 hp Gale motors

1951 14 hp motor

1951-1972 15, 18, 20, 25 hp motors

1973-1976 18, 20, 25 hp motors

The key is parallel with the taper..

I have been wring before, but pretty confident on this one.

Regards

Richard

http://www.richardsoutboardtools.com
classicomctools@gmail.com

[frankr]

Perhaps a word about the reasoning behind it all will help.

On small motors the key is installed parallel with the taper. That causes significant protrusion from the crank surface at the lower end, because it locates the cam as well as the flywheel. It also gives deeper depth into the flywheel keyway.

On 1962-up Big Twin series, the shaft and flywheel hub diameter were increased. But they couldn’t increase the O.D. of the hub because it still had to fit between the coil laminations. So, if they had increased the I.D but not the O.D, that means the hub wall gets thinner at the lower end. Furthermore, if the keyway in the hub were parallel with the taper, it would come dangerously close to cutting the hub wall in half at the lower end. So, the solution was to use a short key and keep it close to the upper end of the taper, and cut it parallel to the centerline of the shaft Thus, the keyway in the hub barely makes it to the lower end and does not weaken the hub wall.

Summing up, small motors key parallel with the taper, 1962-up over 28hp motors parallel with the shaft centerline.

Hope that’s right.

[bobw]

Richard and Frank, thanks for the clarifications on the key installation. It certainly makes sense that the change in shaft and flywheel hub diameter on the 62-up motors would require a different key and installation layout.

Bob

1937 Champion D2C Deluxe Lite Twin
1954 Johnson CD-11
1957 Evinrude Fastwin 18
1958 Johnson QD-19
1958 Johnson FD-12
1959 Johnson QD-20

“Every 20 minute job is only a broken bolt away from a 3-day project.”
"Every time you remove a broken or seized bolt an angel gets his wings."

[garry-in-michigan]

The hub taper on these motors is slightly different from the taper on the crank making them tighter at the bottom. These also require a higher torque on the flywheel nut. This causes the flywheel hub to stretch to fit the crank taper and gives a REALLY tight fit so there is no load on the woodruff key. On the other models, the key helps keep the flywheel in place. On the small key models, the hub does this job. That these flywheels are Hell to get off attests to the fact that the system works. . . 😆

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