1970's-ish 20HP Johnson Seahorse. Questions + "what do i need to know?"

[waterpotter]

Just picked up a 20hp seahorse from the 70's or somewhere in there. Got it to fire up but had a few questions.

The first question is really general: Anything in particular I need to know about these motors? I ran it on 50:1 and it seemed ok, PO said he ran it on 50:1 and my other seahorse from who knows what year also runs on 50:1 so i figured that seemed safe. Any other tips/general knowledge about these guys?


I also have some more specific questions.

First, a shot of the thing in general:



There's a black piece of plastic on the upper left of the shot. Here's a close up:



It looks like it's been chewed up and when I first got the motor I could turn the flywheel by hand but it felt locked up with the pull start. Figured out that this plastic piece was between the pull start and the flywheel. I pulled it back and pulled it on the outside of a metal bar that looked like it was supposed to hold it back from slipping between the wheel and pull starter. Anyone know what this piece is for? It looks like the metal retaining bar thing CAN be pulled to allow this plastic piece to slip underneath, but I couldn't find the control to move the bar. What is this for?


Another question:
My throttle seems like it has a really short pull. It goes barely past "fast" and there's an arrow that implies that I should be able to turn it further. After some inspecting I found that when I turn the throttle it spins a "ring"/"bar" thing that sits over the flywheel and there's a nub that hits a bar. It looks like I should be able to turn the throttle waaaay past that (I can get it much further by hand) but I can't figure out the purpose of the bar or figure out how to move it.

Here's a shot of the throttle in the "slow" position:



And here it is in the "fast" position, as far as I can get it. You can see the bar that swung around and is now hitting the other metal bar/nub thing:



What is this bar for? It looks like there's a set screw thing in the foreground of the picture, but this screw doesn't seem to affect the bar at all despite being attached.
I had a slight moment of thinking maybe this bar was centrifugal, and when the motor was going the bar would move out of the way? But that seems overly complicated.


Any guidance on these issues would be very much appreciated.

Thanks!!

 

[racerone]

The black plastic bit is there to prevent pulling the motor over when it is in gear or the throttle advanced too far.---Think safety here.------Throttle can only be advanced so far in nuetral. ---Must be in forward to get full throttle.

 

[waterpotter]

ah thanks. exactly what I was looking for. Appreciate it!

 

[F_R]

Don't know if this applies to your particular motor or not, but the early ones had a problem with that starter lockout. The rocker that the adjustment screw pushes on would bend under constant spring pressure, then the lockout wouldn't unlock the starter. So,,,,if you experience that problem replace the rocker.

Motor has to be in forward gear before you can advance the throttle all the way. If you can't put it in forward gear (not running) twirl the prop a bit.

 

[hardwater fisherman]

With external ignition coils it should be a 1973 model. I believe they were only made that one year.

 

[racerone]

That particular motor was marketed as a 25 in most areas.---But marketed for a few years after 73 in some areas as a 20 hp.

 

[TN-25]

Bingo! The 20 was last offered in the U.S. in 1973, but surprisingly it was still offered in Canada & Europe beyond that. The ignition setup shows that it as a 1973+ motor. The 20 was not shown in the 1974 brochure, but in my 1975 Canadian brochure it was offered as an exclusive Canadian motor (along with a built-in A/C power adapter). Definitely the color shows as a 1972 - 1975 color known as Anniversary Gold. I have a 1974 Parts Book for a 20, yet at the dealers in 1974 I never saw a single 20.


There was never a form of generator or alternator, yet the 20 came with a specific 45 watt AC adapter. The Inuits loved these motors on the back of their 20' freighter canoes over the ice flows. Seriously they did...