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Johnson 40hp help

A

antjacobs

New member
Hi all, firstly thanks for all your help with my evinrude troubleshooting.. Now time to get the 40hp motor i have sorted.. I did think it was a Mercury but just looking at pic's and it is a Johnson 40hp I'll attach a pic.. Question is how difficult is it to get running without connecting the whole wiring harness, can it be bypassed just to get it running for a test..

Thanks :)
 
Looks like an 85 model.-------------You should hook up a battery to protect the charging system.--------------It will run without the rest of the controls hooked up.----------------If it starts you may have to let it run out of fuel to stop it.------------Hook up water to protect the pump.
 
It should start if you just jump the starter but like was said you need it connected to a battery if it starts. You can disconnect the yellow wires from the stator to the rectifier and run it just make sure no wires short to ground when it is running. You can also jump the starter and just do a compression test if it has good compression everything else can be fixed.
 
Turns out the Johnson is seized, taken the plugs out and put a lot of oil in the cylinders. Going to allow it to do it's job and get a socket and long bar on the flywheel nut and see if it will free up.
 
Pull the gearbox and see if she turns first. If not pull the head and spray it good with WD and use a chunk of wood and a hammer to loosen the pistons first. I never use the flywheel nut to turn the crank put a large strap wrench on the flywheel works better and you wont damage the threads on the crank in case the crank bearings are still good. Pulling the head should tell you if the engine has been flushed properly and if it needs to be bored over with new pistons. Do not force it or you will likely damage the crank and bearings.
 
Does the flywheel turn back and forth even a wee little bit , yes or no ?-------------If there is no motion whatsoever you may have bearing problems.
 
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