What size shear pin in a '57 Johnson?

[BanjoRed145]

What size shear pin do I need for a 1957 35 Horsepower motor? Also, what spark plugs should I be using? The model number is RDE-19.

 

[1946Zephyr]

Re: What size shear pin in a '57 Johnson?

The manual calls out a J4C, but I don't think those are good for anything but fishing weights. I would go with a J6C

Not sure about shear pin size though.

 

[ezeke]

Re: What size shear pin in a '57 Johnson?

The Champion J6C is the recommended spark plug.

http://continuouswave.com/whaler/reference/BRP/SparkPlugChart2008.pdf

The drive pin is #0304575

 

[1946Zephyr]

Re: What size shear pin in a '57 Johnson?

Odd....mine shows the J4J, but that's okay. J6C is much better anyhow

 

[BanjoRed145]

Re: What size shear pin in a '57 Johnson?

Great! Thanks a lot, I have a generic shop manual and wanted to make sure that I had the right plugs for this engine.

 

[restornator]

Re: What size shear pin in a '57 Johnson?

If by shear pin you mean flywheel key, you cannot use the ones at hardware stores. They aren't hardened nor strong enough. Just take your year and model number to a dealer and they'll give you the correct pin

 

[F_R]

Re: What size shear pin in a '57 Johnson?

If by shear pin you mean flywheel key, you cannot use the ones at hardware stores. They aren't hardened nor strong enough. Just take your year and model number to a dealer and they'll give you the correct pin

"Shear pin" refers to the pin used to drive the propeller. Actually, the motor in question does not have a "shear" pin, but a "drive" pin. It is made of stainless steel and is not intended to shear except possibly under very severe circumstances. The rubber hub in the propeller absorbs other shocks and impacts.

OK, having preached all that, the drive pin is part number 304575 and is 1/4" diameter x 1-15/32" long, stainless steel. Used in 28-33-35-40hp motors for many years

 

[MudLake]

Re: What size shear pin in a '57 Johnson?

The manual calls out a J4C, but I don't think those are good for anything but fishing weights. I would go with a J6C

Not sure about shear pin size though.

I was always told by the marine shops that the higher the number the hotter the plug. Is this your experience? I'm told it is because the center electrode insulation is thinner or fatter. The fatter insulator will dissipate the heat faster so it is a colder plug Therefore it may be a C4J as compared to a C6J.

I am not going to run thermos-stats for a while until I see how my twin 61 Johnsons are going to operate so I may try the C6J series plug for a hotter heat range.


Do you think my analogy is correct.

cheers

 

[F_R]

Re: What size shear pin in a '57 Johnson?

I was always told by the marine shops that the higher the number the hotter the plug. Is this your experience? I'm told it is because the center electrode insulation is thinner or fatter. The fatter insulator will dissipate the heat faster so it is a colder plug Therefore it may be a C4J as compared to a C6J.

I am not going to run thermos-stats for a while until I see how my twin 61 Johnsons are going to operate so I may try the C6J series plug for a hotter heat range.


Do you think my analogy is correct.

cheers

You are correct,it is all about how fast it gets rid of the heat. You need Some heat to burn off the contaminates, but too much heat will also burn up the plug---and cause pre-ignition/engine damage.

And then we get into the Great Spark Plug Debate. Ane we haven't even touched the Great Thermostat Debate.

 

[restornator]

Re: What size shear pin in a '57 Johnson?

"Shear pin" refers to the pin used to drive the propeller. Actually, the motor in question does not have a "shear" pin, but a "drive" pin. It is made of stainless steel and is not intended to shear except possibly under very severe circumstances. The rubber hub in the propeller absorbs other shocks and impacts.

OK, having preached all that, the drive pin is part number 304575 and is 1/4" diameter x 1-15/32" long, stainless steel. Used in 28-33-35-40hp motors for many years

Oh okay. I had a drive pin fail, but the prop's hub was so worn, it had about 1/4inch of play, it looked like a bow tie

 

[ezeke]

Re: What size shear pin in a '57 Johnson?

The spark plug for this motor as shown in the earlier factory manual was revised in 1979 by Service Bulletin #1419 Rev 2. The revision recommended plugs were Champion J6J, or AC M44C; gap = .030.

The J6C superseded the J6J and is currently the recommended plug.

 

[rjezuit]

Re: What size shear pin in a '57 Johnson?

Not that I like correcting people, but the flywheel keys are supposed to be soft, not hardened. The taper is what provides the "lock" between the crank and flywheel, the key is for position only so your timing is correct. If torqued correctly, you do not even really need the key theoretically. A lot of them are made from aluminum so they shear when you hit something hard. Rick

 

[ezeke]

Re: What size shear pin in a '57 Johnson?

Not that I like correcting people, but the flywheel keys are supposed to be soft, not hardened. The taper is what provides the "lock" between the crank and flywheel, the key is for position only so your timing is correct. If torqued correctly, you do not even really need the key theoretically. A lot of them are made from aluminum so they shear when you hit something hard. Rick

We are not speaking of the crankshaft (flywheel) key. The drive pin a/k/a shear pin is used to connect the propeller to the propeller shaft on the pin drive gearcases.

In cases where the drive pins broke, it was often because the propeller was not mounted correctly.