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1996 Johnson 48 SPL cannot maintain speed above idle

dfmanley

New member
Hi all,

first post so please bear with me I have read through a lot of the forum to try troubleshooting my issues but this one really has my brain in a knot.

My 48 spl will work great for about 3 or 4 minutes as I come past idle from the engine being cold, as soon as it warms up it goes into some kind of slow mode where I can barely travel at idle speed.

After the initial 3 or 4 minutes of running if I let the engine cool I can get another 3 or 4 minutes but otherwise if I come back down or turn the engine off and try to come back up right away I immediately go back into whatever rev limiting mode it is in.

I have gone through all the basics, it has good gas, good electricity, good compression 120 on both, I cleaned out the cooling passages and impeller. The last test I did today was run the engine without the temperature switch plugged in, not for long just to see if I could isolate the component, however the engine immediately went into slow mode.

That said I can run just a little above idle without any issue for as long as I want, at kind of like a fast no wake zone speed. My issues really come at anything past like 1/3 throttle and above.

Also I bought the seloc manual and went through all the low speed idle adjustments and such by procedure, carbs are spotless. After all the adjustments it idles perfect and sounds much better than it does in the video, however it still has the same issue.

Thanks for all help in advance and just for reading my lengthy explanation.
 
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Run with a timing light to see which cylinder has spark issues.



I did actually and both spark plugs had what I would only be able to describe as an erratic spark. Like sometimes it was many in quick succession and sometimes it wouldnt light up for a while. But definitely no consistent spark matching a spot on the fly wheel.
 
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