Interpreting an expansion plug number?

[amuller]

J2457020

This is on a Johnson 40 hp. Can anybody help me confirm that and get the details?

[Anonymous]

As a serial number, that would make it a 1961

The 40hp models made that year were:
RD-23
RDL-23 long shaft
RDS-23 electric start
RDSL-23 electric start, long shaft

The hood would be white fiberglass (with silver on top)

[amuller]

It is electric, but hood details are different.

Would this be in the range that had a weak crank for 40 hp? How does one know?

[Anonymous]

The hood looks like it could be 1964, But I would expect that all the 1960’s 40hp covers would interchange:

https://web.archive.org/web/20050826170 … _1964.html
https://www.youtube.com/watch?v=gNVqTQXztkAB

Finding the model number, which would begin with "RD" on the block plug, or the transom bracket, would be the BEST indication of the year.

I think 1962 was the year with the heavier crank.

Wait, the last serial for 1961 is 2,249,094 so J2457020 is later, and could well be 1964!

[outbdnut2]

Compare that serial number with the one on the ID plate on the transom clamps (if it hasn’t been removed). If it doesn’t match, someone swapped powerheads. The ID plate should also have the model number.
Dave

[frankr]

Small crank used a 7/8" wrench to remove flywheel. Large cranks use a 1-1/16" wrench. So, look at the nut

[amuller]

It is an RDS-26R.

[Anonymous]

quote amuller:

It is an RDS-26R.

1964

[garry-in-michigan]

That would definitely be the big crankshaft – no worries. . . 😉

[amuller]

Well, I bought it. $100 but whether it is a runner remains to be seen. It’s obviously felt some significant Mickey Mousing.

Quick compression test didn’t give consistent results–varying in the range of 60 to 80 for both cylinders.

There seems to be a freeze crack just above the skeg. could be all junk inside.

The pump on it is the little square one. This doesn’t seem right–do these pumps move enough fuel for 40 hp?

How hard is it to remove a 5" leg extension? Water tubes and driveshaft I presume have to change. Anything else?

Thanks, as usual.

[Author]

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