Topic: 1972 johnson 4 hp bear to start – Antique Outboard Motor Club,Inc

This topic has 10 replies, 7 voices, and was last updated 8 years, 9 months ago by fleetwin.

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July 18, 2015 at 1:20 am #2040
billy-t
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Hi I have a 4 hp that is very hard to start, runs great and idles down when you do get it running. A while back mumbles suggested to plug one of the holes in the choke valve, so hat i did was change it out for one i had in the parts bin, that only had one hole, but it didnt seem to make any real difference, just about pulled my arm off even when it was warm?

Any other thoughts would be appreciated.

Bill
July 18, 2015 at 1:24 pm #20343
The Boat House
Participant
- This reply was modified 5 years, 5 months ago by The Boat House.
- This reply was modified 3 years, 2 months ago by The Boat House.
July 18, 2015 at 3:05 pm #20346
jeff-register
Participant
US Member - 2 Years
A few years back I built a 1974 Johnson 4hp. It was hard to start too until I learned not to flood it. Once the carb was set it fires right up.
July 18, 2015 at 5:03 pm #20348
frankr
Participant
US Member
A nice feature of those motors is you can’t find the start position on the throttle. So give it a little more than you think you should. Another nice feature is the recoil starter. Never mind what the book says, give it a series of short hard yanks.
July 18, 2015 at 5:32 pm #20350
johnyrude200
Participant
I’ll 2nd and 3rd those previous posts. Those motors can be a PIA to start when cold/dry/not run for awhile. Even with strong spark, they just need more pulls to kick off. Once their going, you’re all set (until the next long-term lay off!).

I will say, if the carb low-speed is set wrong, they just won’t start at all. Follow the service manual setting, that one has been pretty consistent with the ones I’ve worked on, and to Frank’s point, put the throttle up as far as it will go. Worst thing you can do is throttle down after it pops off right away (of course, if you’re on the boat, make sure everyone is holding on…given it’s a direct drive!).
July 19, 2015 at 1:01 am #20362
billy-t
Participant
Thanks all
July 19, 2015 at 5:32 pm #20394
fleetwin
Participant
US Member - 2 Years
Once the engine gets started, it idles and runs at WOT well? It starts OK hot? Are you sure the choke knob is holding the choke completely closed during cold starts? This linkage is not a very positive one, it would be easy for the choke to slip open a bit while cranking. The only thing that helps keep the choke closed is that flimsy plastic bushing in the motor pan.
July 19, 2015 at 7:50 pm #20400
bob
Participant
FLEETWIN IS RIGHT.I HAVE HAD TWO OF THESE MOTORS,AND THE CHOKE WAS A PROBLEM.HOLD THE CHOKE OUT BY HAND WHEN YOU START THE MOTOR AND SEE WHAT HAPPENS.ALSO THERE IS A SMALL SCREW ON THE CHOKE PLATE(I THINK)THAT IF LOOSENED WILL GIVE YOU A VERY SLIGHT ADJUSTMENT SO THAT THE PLATE WILL LAY FLATTER INTO THE CARB BODY.MAYBE YOUR PROBLEM
July 19, 2015 at 8:16 pm #20401
billy-t
Participant
Okay so looked at it this morning, and thought i could hear a scraping/dragging sound when i was turning the flywheel by hand. So i thought maybe a coil heel was dragging. Pulled the flywheel checked everything, point gaps good. coils were fine. Couldn’t see any issue, but I had a blown 4 hp evinrude in the shed, went and got the flywheel and magneto which had good coils and points and condensers on it already, and Switched over to the Johnson power head torqued it down, put in the barrel started on third pull. No dragging /scrapping sound now. Starts good hot or cold. Not sure what the issue was, could flywheel be warped? Will have a closer look but nothing really jumps out as an issue. New one for me that is for sure.

Bill
July 19, 2015 at 8:32 pm #20403
johnyrude200
Participant
check the bottom of the flywheel on the original for wear marks, was the dragging/scraping noise consistent during the entire revolution or only intermittent during 1 part (or 2) of the revolution?

The reason why I ask, is that when the magnet passes the coils, you will see the mag plate jiggle, which can account for the scraping noise. If there is slop on the mag plate than it may be slightly tilting toward the magnet as it passes by slowly and dragging.

When the flywheel is turning 1000RPM, I would suspect that magplate is essentially ‘floating’ or in dynamic balance since the magnet is passing both coils so quickly that there isn’t enough time for it to slop/wobble and rub.
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