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'63 Johnson 40Hp 18 Oct 2015 20:12 #53181

Thanks Terry, that was an interesting read.

Maybe Honda will produce some two stroke outboard motors in the future.
1958 Vagabond, 1954 Vagabond, 1958 Rocket Runabout, 1958 Clipper, 1950 Fire Fly, 1953 Flyer, 1954 Deluxe Runabout, 1956 Alumacraft Cruiseabout, 1956 Alumacraft Merrie 16, 1958 Alumacraft Queen Merrie, 1956 Alumacraft Deep C, 1958 Alumacraft Deep C, 1951 Alumacraft Model R, 1956 Alumacraft FD.

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'63 Johnson 40Hp 18 Oct 2015 14:03 #53171

I did some research into this .
Seems one solution to runaway is to open the throttle all the way.

And this was a good read on two stroke emissions.
www.motorcycle.com/manufacturer/honda/honda-exp2-14293.html

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'63 Johnson 40Hp 17 Oct 2015 22:35 #53153

Just guessing but likely with the butterfly open at full throttle the crankcase vacuum will not be high enough to trigger the protection cutout even with no prop.

Another guess is that when backing off from full throttle the circuit may kick in killing one cylinder for a short time. May sound funny.

Other than that I can't see why OMC would have spent for a Hg switch when it wasn't needed.

It will be interesting to see what you get.
1958 Vagabond, 1954 Vagabond, 1958 Rocket Runabout, 1958 Clipper, 1950 Fire Fly, 1953 Flyer, 1954 Deluxe Runabout, 1956 Alumacraft Cruiseabout, 1956 Alumacraft Merrie 16, 1958 Alumacraft Queen Merrie, 1956 Alumacraft Deep C, 1958 Alumacraft Deep C, 1951 Alumacraft Model R, 1956 Alumacraft FD.

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Last edit: Post by VinTin.

'63 Johnson 40Hp 17 Oct 2015 17:21 #53146

My understanding is that 2 stroke motors can go into runaway condition when the load is removed suddenly. That's why they monitor the vacuum pressure to shut down one cylinder to prevent it.
With the dual Hg switch I would sure hate to lose the prop at WOT. It would be a short time before detonation! :ohmy:
I think I'll just skip that switch when wiring up the harness.

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Last edit: Post by FishbonzWV.

'63 Johnson 40Hp 17 Oct 2015 17:02 #53145

I hope this scan is more clear than the last one I sent. If you left click on the image it gets bigger and easier to read.


John

1958 Vagabond II & 35 HP Evinrude
1955 PlastiCraft 12 Ft. Delux Runabout
1957 Clipper & twin 35 HP Evinrudes
1957 AlumaCraft 14 Ft. FD

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Last edit: Post by Boatboy.

'63 Johnson 40Hp 17 Oct 2015 17:00 #53144

FishbonzWV wrote: Thanks John.
Looking at the diagram, it seems that it removes the ground from the cutout switch which monitors the vacuum pressure. Maybe it prevents the cutout from actuating when running flat out.
????????


My understand is that you are correct.

When letting off of the throttle after running at high speed it prevents the cutout from actuating and killing one cylinder. Bet it would sound funny.

The over rev protection circuit only operates at low throttle settings. Evidently there was a problem with the motor reved a little in neutral and when brought back to idle the motor would run away. I've had mine disconnected for a couple of years now with no problems. The wiring to one of the switches had worn out at the switch.
1958 Vagabond, 1954 Vagabond, 1958 Rocket Runabout, 1958 Clipper, 1950 Fire Fly, 1953 Flyer, 1954 Deluxe Runabout, 1956 Alumacraft Cruiseabout, 1956 Alumacraft Merrie 16, 1958 Alumacraft Queen Merrie, 1956 Alumacraft Deep C, 1958 Alumacraft Deep C, 1951 Alumacraft Model R, 1956 Alumacraft FD.

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Last edit: Post by VinTin.

'63 Johnson 40Hp 17 Oct 2015 16:41 #53142

Chemical symbol for Mercury metal

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'63 Johnson 40Hp 17 Oct 2015 16:34 #53141

Terry, I am not sure what an Hg switch is
John

1958 Vagabond II & 35 HP Evinrude
1955 PlastiCraft 12 Ft. Delux Runabout
1957 Clipper & twin 35 HP Evinrudes
1957 AlumaCraft 14 Ft. FD

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'63 Johnson 40Hp 17 Oct 2015 16:32 #53140

Thanks John.
Looking at the diagram, it seems that it removes the ground from the cutout switch which monitors the vacuum pressure. Maybe it prevents the cutout from actuating when running flat out.
????????

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'63 Johnson 40Hp 17 Oct 2015 16:23 #53139

Normally that safety switch is mounted so it is actuated by the shift lever.
These Hg switches are mounted side by side on the throttle shaft and share a common ground.
I can't think of anything that needs to be disabled at WOT.

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