Topic: 57 Johnson Javelin runs and then stops after about 40 seconds

This topic has 19 replies, 10 voices, and was last updated 3 years, 11 months ago by fleetwin.

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April 26, 2020 at 9:44 pm #201162
h20lew
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US Member
I have a 57 Johnson Javelin that I put together with different parts and pieces. Replacement powerhead with good compression on both cylinders, rebuilt carb, new ignition components and plug wires. I can get it to start and run just fine for about 40 seconds to a minute, but it then it hesitates with a sputter and and then kills. If I try to restart it right after it won’t start. If I let it sit for an hour, I can start it again with but it repeats the same behavior. I have a number of new variables I’m working with, seems carb related – just looking for suggestions on what to look at first.
April 26, 2020 at 9:56 pm #201164
dave-bernard
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US Member
sounds like fuel to me. do you use the primer bulb on the restart?
April 27, 2020 at 7:26 am #201172
Randy in Tampa
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The second it stops running disconnect the fuel and unscrew the high-speed jet and see if any fuel comes out if it doesn’t there’s an issue with fuel getting into the bowl which could be a number of things

Rotary valve Johnson’s Rule!
April 27, 2020 at 7:42 am #201173
frankr
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US Member
Using the pressure tank?? Does it build pressure in the tank?? Tried re-pumping the primer button before it quits??
April 27, 2020 at 7:43 am #201174
kerry
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US Member
I agree with Dave. Sounds like its running on whats in the float bowl. If using a pressure tank, is it making pressure? When engine dies, unscrew cap and see if it releases pressure. If no, check hoses for leaks/plugups, tank gaskets for seal. If ok, prime float bowl then disconnect line at carb, put line in container to catch fuel, and start. If fuel comes out, carb issue. No fuel, trace it back to tank. If a fuel pump, are you tank testing with the tank on the ground? Did a FP conversion on a ratty Fleetwin years back, had same issue. Turns out the pump (Mikuki) couldn’t “lift” the fuel that high. Put tank on a five gallon bucket, ran great.

If you have too many, AND not enough, you're a collector.
April 27, 2020 at 7:44 am #201175
kerry
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Frank beat me by one minute! Sorry, I type slow.

If you have too many, AND not enough, you're a collector.
April 27, 2020 at 10:03 am #201179
seakaye12
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US Member
I had an issue last week with the check valve going bad behind the reed plate. It is made of a rubber-like material and it had snapped in two. The engine obviously could no longer pressurize the tank. Ran 40 seconds and quit….just as yours is….
April 27, 2020 at 10:39 am #201187
crosbyman
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Canada Member - 2 Years
that was a tricky one for certain how and when did you decide to operate on the check valve

I have never seen this issue come up before on aomci or iboats forums …

Joining AOMCI has priviledges 🙂
April 27, 2020 at 1:59 pm #201220
h20lew
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US Member
Thanks guys for the input. I forgot to mention I did a fuel pump conversion on it. Newer OMC pump and it’s a larger one rated for motors of this size. And the priming bulb holds on the initial start – but this suggestion caught my eye:

“Turns out the pump (Mikuki) couldn’t “lift” the fuel that high. Put tank on a five gallon bucket, ran great.”

I’m running this on a stand with a garden hose adapter to supply water and with the fuel tank on the ground…. so the lift sounds like it might be a possible culprit. ‘lI”try it again with the tank elevated and see if I get better results. I’ll also try the high speed needle check and report back.
April 27, 2020 at 2:18 pm #201222
lloyd
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US Member
Following my usual list of priorities when diagnosing a running problem. They are compression, then ignition, then fuel delivery/carburetion, in that order. Sounds like we can safely eliminate compression in this case. But we haven’t considered ignition, and I have seen this same set of symptoms in motors with bad condensers. Starts and runs ok for a short time, then dies and after a while the cycle repeats. Did you check for spark right after it died??? May well be fuel delivery, but quick and easy to check the ignition.
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