Topic: 1956 Johnson 30 HP. shear pin brass or monel?

This topic has 10 replies, 6 voices, and was last updated 8 years, 8 months ago by frankr.

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August 20, 2015 at 3:39 am #2314
billy-j
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US Member - 2 Years
I have a 1956 Johnson 30 HP. What would be the correct shear pin material brass or monel ? Thanks Bill,
August 20, 2015 at 3:45 am #22385
wedgie
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Check out this thread Billy. 😉

viewtopic.php?f=5&t=2328&p=13611&hilit=shear#p13611
August 20, 2015 at 4:30 am #22388
garry-in-michigan
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August 20, 2015 at 5:21 am #22389
frankr
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As you can see, 1956 was a year of change. The propeller was changed to allow slippage under impact, and a Monel pin went with it. The reason of course was to eliminate shear pin breaking and the need to replace it on the water. At the same time the prop nut was changed to accept a longer pin. So, actually, it depends on what prop you have on it and does it have the correct nut to go with it. I suppose it depends on run what you brung on the prop and use the pin that fits the nut. If you have concerns about doing that, use brass.
August 20, 2015 at 5:30 am #22390
Mumbles
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Check your serial number. ’56 was the year OMC made mid-year changes and the RD-Big Twin shear/drive pins were among the changes. I believe this is when they started using rubber hubs in the prop and a stainless drive pin to match it. The earlier models used a bronze shear pin.

Here’s a snip from a Johnson book explaining to use the later 304575 drive pin with the earlier props. If you don’t want to do that, a piece of brass rod would work.
August 20, 2015 at 3:28 pm #22400
billy-t
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This is interesting and a timely post for me as well. I have a RD-18 and the prop nut wont screw on far enough to allow the cotter pin to be placed in it. It appears that I have the ss drive pin and not sure as to which prop it is as there are no numbers of any value on it. Serial number is 1338617 so I am assuming I need to make sure I have thrust washer 304576 along with Propnut 376731.
gheez something should work this week..
August 20, 2015 at 5:05 pm #22404
frankr
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A tid-bit of info on those props & pins. Since the prop can spin on the hub under extreme overload, it can tend to move off the end of the hub. The long drive pin sticking out both sides of the hub prevents that from happening. The thrust washer between the pin and prop acts as sort of a bearing. I have seen lots of cases where a short pin was used and the prop spun out over the ends of it, so you couldn’t get the pin out. A real inconvenience if the pin is sheared.
August 20, 2015 at 5:48 pm #22405
billy-t
Participant
Thanks Frank

I am confused on part numbers though, looking at Mumbles post I see the mention of Propnut 305294 which isnt mentioned on the marineengine parts listing only 375773 and then going to 376731 after the introduction of the longer ss pin.

Help!!
August 20, 2015 at 7:20 pm #22408
frankr
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US Member
375773 thru early 1956 (short pin)
376731 late 1956 > (long pin)
305291 is the plastic nut that came out in 1958 or 1959 > (takes a different prop shaft)
TYPO CORRECTION 305291 should be 305294, a plastic cone "nut" came out in 1958-up
August 21, 2015 at 2:27 am #22428
billy-j
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US Member - 2 Years
by FrankR » Thu Aug 20, 2015 1:21 am
As you can see, 1956 was a year of change. The propeller was changed to allow slippage under impact, and a Monel pin went with it. The reason of course was to eliminate shear pin breaking and the need to replace it on the water. At the same time the prop nut was changed to accept a longer pin. So, actually, it depends on what prop you have on it and does it have the correct nut to go with it. I suppose it depends on run what you brung on the prop and use the pin that fits the nut. If you have concerns about doing that, use brass. ————————————————- VERY CONFUSING on what would be proper at this stage in the game. My engine is a 1956 Johnson 30 HP. and the propeller I am using was a NOS Johnson seahorse green prop. I bought the pin using the part number as per a original 1956 parts breakdown catalog and it was what I thought was a Monel pin which surprised me as I had this engine many years and I would make the shear pins out of a 1/4 ” dia. brass brazing rod. How would I know what would be proper now? Bill,
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