Anyone know where to find Johnson test wheels?

Mikeyboy

Chief Petty Officer
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Mar 15, 2012
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475
I am looking for a test wheel for my 75 Johnson 135 hp motor. The service manual says its part #386246. I'm trying to set the timing on the motor and the manual says the motor needs to be run at 43-4600 rpm to do it and I really don't want to do that in the tank. Seems like a dumb idea.
 

tx1961whaler

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May 31, 2008
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5,197
Re: Anyone know where to find Johnson test wheels?

An easier way to time it without it running, courtesy of Joe Reeves (not me..)

------------------
(Timing At Cranking Speed 4?)
(J. Reeves)

NOTE: If your engine has the "Fast Start" feature", you must disconnect/eliminate that feature in order to use the following method. The "Fast Start" automatically advances the spark electronically when the engine first starts, dropping it to normal when the engine reaches a certain temperature.

The full spark advance can be adjusted without have the engine running at near full throttle as follows.

To set the timing on that engine, have the s/plugs out, and have the throttle at full, set that timer base under the flywheel tight against the rubber stop on the end of the full spark timer advance stop screw (wire it against that stop if necessary).

Rig a spark tester and have the gap set to 7/16". Hook up the timing light to the #1 plug wire. Crank the engine over and set the spark advance to 4? less than what the engine calls for.

I don't know the full spark advance setting your engine calls for, but to pick a figure, say your engine calls for 28?, set the timing at 24?. The reasoning for the 4? difference is that when the engine is actually running, due to the nature of the solid state ignition componets, the engine gains the extra 4?.

If you set the engine to its true setting at cranking speed, when running it will advance beyond its limit by 4? which will set up pre-ignition causing guaranteed piston damage! You don't want that to take place.

No need to be concerned about the idle timing as that will take care of itself. The main concern is the full advance setting.

Be sure to use your own engines spark advance settings, not the one I picked out of the air here in my notes.
 

F_R

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Re: Anyone know where to find Johnson test wheels?

Mikey, you have a PM.
 

Mikeyboy

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Re: Anyone know where to find Johnson test wheels?

Thanks a lot for all the info
 

Faztbullet

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Mar 2, 2008
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15,930
Re: Anyone know where to find Johnson test wheels?

Just get ya a old prop and cut 1-1/2 "off tips...Ta Da test wheel !!!
 

Mikeyboy

Chief Petty Officer
Joined
Mar 15, 2012
Messages
475
Re: Anyone know where to find Johnson test wheels?

That or I could get myself a shiny new prop and cut this one down. I'm always looking for a good excuse to buy shiny new parts lol.
 

F_R

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28,226
Re: Anyone know where to find Johnson test wheels?

Mikey, check your PM's again. I added something.
 

boobie

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Nov 5, 2009
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Re: Anyone know where to find Johnson test wheels?

Fazt, I see you know about that old trick too, but it depends on the hp on how much you cut off. Done it before, especially on Yamahas.
 

Mikeyboy

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Mar 15, 2012
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Re: Anyone know where to find Johnson test wheels?

How much should I cut off for a 135 hp motor?
 

boobie

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20,826
Re: Anyone know where to find Johnson test wheels?

This is not etched in stone. On an alum 13x19 prop you cut it so you have a 4.5 " radius from the center of the prop to the tip of the blade. This is for v-4's No Warranty !
 

Mikeyboy

Chief Petty Officer
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Messages
475
Re: Anyone know where to find Johnson test wheels?

Thanks boobie. Gotcha on the no warranty.
 
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