1979 johnson 140hp runs great in yard cannot get over 5 mph in lake & won't start.

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rdprttt

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1979 johnson 140hp runs great in yard cannot get over 5 mph in lake & won't start.

I had the fuel pump & carburetors rebuilt, replaced the powerpacks, stator and timerbase new plugs, new wires.
Boat starts up & runs great with muffs in yard. Won't go when in lake & eventually stalled out.

I checked the compression and it was good on all cylinders while in my yard, no oil leaking from heads.

I went to the lake today put the boat in the water it started up fine, but when I put in forward I couldn't get up to speed and it would stall out when I went to far forward with the throttle.

Can anyone help me? I really thought I had it in good shape.

Appreciate any help you can give.

Thanks,
Bob
 
JB

JB

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Re: 1979 johnson 140hp runs great in yard cannot get over 5 mph in lake & won't start

Re: 1979 johnson 140hp runs great in yard cannot get over 5 mph in lake & won't start

Howdy.

First of all, accept that your outboard does not run well with no load, it just fakes it. Outboards are very good at pretending to run on all cylinders when in reality they may be running on one or two.

You are probably running on 2 cylinders. . .maybe only one.

What happens if you squeeze the primer bulb?
What happens if you squirt premix fuel into each carb?
What happens if you pull (carefully!!) each spark plug lead, one at a time?

All of the above with the engine in gear, in the water.
 
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wired247

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Re: 1979 johnson 140hp runs great in yard cannot get over 5 mph in lake & won't start

Re: 1979 johnson 140hp runs great in yard cannot get over 5 mph in lake & won't start

Keep in mind that when you run it on the muffs you never actually open the throttle plates. There is no exhaust back pressure or resistance from the propeller. It will idle and rev up on as little as one cylinder.
 
86 century

86 century

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Re: 1979 johnson 140hp runs great in yard cannot get over 5 mph in lake & won't start

Re: 1979 johnson 140hp runs great in yard cannot get over 5 mph in lake & won't start

What are the compretion numbers.

Have you checked the spark with a tester.
I have seen a few that will spark the plug out of the cyl but once it get in the turbulance of the combustion chamber it stops.
 
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emdsapmgr

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Re: 1979 johnson 140hp runs great in yard cannot get over 5 mph in lake & won't start

Re: 1979 johnson 140hp runs great in yard cannot get over 5 mph in lake & won't start

When you get the boat down in the water, put an inductive timing light probe on each plugwire when it is running. The flashes in the gun will tell you a lot about the quality of the spark from the coils. It will show no fires, weak firing, intermittents.
 
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wolfblake21

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Re: 1979 johnson 140hp runs great in yard cannot get over 5 mph in lake & won't start

Re: 1979 johnson 140hp runs great in yard cannot get over 5 mph in lake & won't start

I had this same problem with an 89 Evinrude 150. I had a couple different problems, the first problem was a fuel line that had a crack in it. It never leaked in the yard, it wasnt until I had my hood pulled off and my wife watching the motor that she saw fuel squirting out. I fixed my fuel line problem and I thought I had it fixed. Took it out, and the same thing happened. I tore into my carbs and found a blockage in my fuel inlet. After fixed that, the motor ran perfect!
 
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