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Brand new 1967 Johnson 20hp


Bud9051's Avatar
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ME

03-17-09, 06:04 AM   #1  
Brand new 1967 Johnson 20hp

Greetings, a few years back I picked up a Johnson 20 that had two tanks of gas through it and then put in storage and never touched again. Replaced points plugs, condensers, and coils and cleaned the carb. I have an Evinrude Fast Twin 18 so have done carbs several times before, a lot easier than a rochester 4 barrel. Anyway, Started up first pull and seemed fine, pumping water great although I know the impeller should be replaced. Took it out for a test run and it would bog down immediately. Could not get any power at all. Coasted back to the dock at idle and it has been waiting for me to fix it for several years. Now is the time

Suggestions? clean carb again? replace seals? fuel pump (never done)?

P.S. have book and have worked on small engines before.

TIA
Bud


Last edited by Bud9051; 03-17-09 at 06:06 AM. Reason: additional
 
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03-17-09, 01:35 PM   #2  
did you try squeezing the fuel bulb to see if power increased?
something this old dont suspect the fuel pump to be much good even though it was used very little. would probably start there.

 
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03-17-09, 02:48 PM   #3  
Hi Bjay

Tried the bulb, no improvement. Looking for issues related to setting unused for a long time. I am also sure it wasn't drained or prepared in any way for storage. The coils had literally fallen apart so I'm concerned that other parts may have done the same. I will be picking up a kit for the fuel pump and replacing the water impeller. And cleaning the carb again just in case.

Bud

 
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03-17-09, 08:22 PM   #4  
Check timing to make sure it isn't the problem. What did the spark plugs look like after the test run? If pumping the primer doen't help I would look at spark as being the problem. Have you done a compression test?

 
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03-18-09, 06:07 AM   #5  
Compression test is high on my list. Timing is kind of a no-brainer and have done it many times on the old 18 so fairly confident that was ok. I have read that lower chamber pressure could be a problem as the seals can dry out. Never gone that far into my other motor, but may have to here. Any thoughts on how that would relate to the starting and idling great but bogging down under power symptoms?

Bud

 
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03-18-09, 07:05 PM   #6  
I would think the seals being out is a bit of a long shot since there wouldn't be any ethonol in the fuel back then.
I just thought about it and is there a high and low speed coil under the flywheel?

 
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03-19-09, 04:45 PM   #7  
"high and low speed coil under the flywheel?" well you got me there! No idea. I will have to wait until I can find/review my book to refresh my memory or later when I get the motor apart again. Still 2 feet of snow in the yard so spring feaver hasn't fully taken hold.

Thanks,
Bud

 
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03-19-09, 07:07 PM   #8  
Ok I talked to my parts guy at work and your motor doesn't have a 2 charge coil setup.

I hear ya about the snow we did have a 70 degree day last week.Beer 4U2

 
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03-20-09, 04:41 PM   #9  
Posted By: samuari Ok I talked to my parts guy at work and your motor doesn't have a 2 charge coil setup.

I hear ya about the snow we did have a 70 degree day last week.Beer 4U2
I had a simeler porblum on one of my old moters that I had not run for a number of years I ended removing the suply line from the tank and found the intake screen parcely blocked restricking the flow at high speed
Just a though

 
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03-20-09, 06:06 PM   #10  
Interesting, thank you. I don't remember checking that and it started and ran so well at idle. Possible.

Bud

 
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