1983 johnson 35 hp twin cylinder

furg69 · Jun 19, 2011

Hey guys new to the site, done a search and seems to be tons of information on here to help people out. I recently bought a 1983 Johnson 35hp, the engine seems to run fine when i fire it up but idles down or revs up without me touching anything on the motor or controls. I can run the engine fine for 10 or more mins but the second i shut it off it wont start until about an hour later. What could cause this ? I tested the spark which seems fine and the compression is at 70 psi on both sides ( im not sure if this is g ood or not). Would it have anything to do with the carb settings or dirty ? it did run fine today in a pond but as soon as i shut it off i had to paddle back. Any help would be great thanks

Monte1961 · Jun 19, 2011

Re: 1983 johnson 35 hp twin cylinder

When was the last time the carb/s overhauled? Over a year or unknown, rebuild with OEM carb kit/s. 70lbs is getting low. Mite want to think about rebuilding.

fireman57 · Jun 19, 2011

Re: 1983 johnson 35 hp twin cylinder

Did you test for spark when it wouldn't start or after you shut if off. I've seen coils that had to cool down before they would work again because they were starting to break down.

furg69 · Jun 20, 2011

Re: 1983 johnson 35 hp twin cylinder

Thanks guys. I called the local repair shop and they said 70 psi is way down for this this engine when warm, i read about people on here using Seafoam to restore compression due to sticky rings, im going to give this miracle juice a try and see what happens from my understanding the engine inst worth rebuilding where it's a 1983.

Monte1961 · Jun 20, 2011

Re: 1983 johnson 35 hp twin cylinder

why is it not worth overhauling?

furg69 · Jun 20, 2011

Re: 1983 johnson 35 hp twin cylinder

well its a 1983 and i just figured it's not worth much more then 300-500 bucks in running condition.

Daviet · Jun 20, 2011

Re: 1983 johnson 35 hp twin cylinder

I would try a good decarb and see if the compression comes up. If it were me I would troubleshoot the system and find the problem. If the engine will start and run the compression is good enough to carry on.
Start it and run it for 10 or 15 min and then shut it down and check spark quickley, is it good?

furg69 · Jun 21, 2011

Re: 1983 johnson 35 hp twin cylinder

Tried de-carbing the engine with seafoam, compression never changed which leads me to believe thats the rings are badly worn. Anyone know how much work is involved in removing the engine and installing new rings ? Im pretty mechanically inclined when it comes to snowmobile engines so i would assume the engines are similar. Thanks again everyone

Daviet · Jun 21, 2011

Re: 1983 johnson 35 hp twin cylinder

If you are going to get into that kind of repairs, I would strongly suggest that you get the FACTORY manual and do some reading and see if you are comfortable doing it. If you have done snowmobile engines, with the guidence of the manual I would think you coulkd do it. I would repair the hot stsrt problem first and see how it runs for you. I have had several engines with the compression a little low and they worked fine for my needs.

AlTn · Jun 21, 2011

Re: 1983 johnson 35 hp twin cylinder

Heck..remove the head and examine the pistons and cylinder walls..if they are passable, check the head with a straightedge for warpage and straightness, then surface the head with 150 or so grit emory paper/cloth taped to a flat surface <glass works well> using a figure 8 motion...replace the headgasket, torque it down, check or replace the thermostat and give it a go. Decarb it again and check the compression. You'll only be out a headgasket and possibly a thermostat. As you probably know, they'll run ok at 70#, just have a funky idle. If you've rebuilt snowmobile engines, this should be familiar enough to you to rebuild w/o much worry, providing you'll invest in the factory workshop manual..OMC is the one I'd recommend...try ebay or kencook.com...parts should be no problem with that recent model.

jasper60103 · Jun 21, 2011

Re: 1983 johnson 35 hp twin cylinder

furg69 said:
well its a 1983 and i just figured it's not worth much more then 300-500 bucks in running condition.

Just an FYI.
Here's a guy who rebuilt a '81 35hp with his son. Priceless!

http://forums.iboats.com/showthread.php?t=422974&page=1

furg69 · Jun 23, 2011

Re: 1983 johnson 35 hp twin cylinder

Heys guys been trying to test the coils and ignition on this engine before i tear it apart. I removed the coils to try some spare ones someone borrowed me but no start at all with the used ones, tried to install the orignials again and now it doesnt start at all maybe i have the grounds wrongs or coils hooked up the wrong way, can someone help me with how they go hooked up exactly. thanks again

AlTn · Jun 23, 2011

Re: 1983 johnson 35 hp twin cylinder

the orange wire with blue tracer goes on the upper coil, then that plugwire goes to the #1 cylinder <upper cylinder>..if you've reversed them, it won't start

furg69 · Jun 23, 2011

Re: 1983 johnson 35 hp twin cylinder

OK thanks so much, but would that stop me from getting spark ? since removing the coil and power pack and reinstalling it i have no spark at all now.

AlTn · Jun 23, 2011

Re: 1983 johnson 35 hp twin cylinder

do you have a black/yellow wire that goes to the power pack?..unhook it and see if the spark returns....that b/y wire is the grounding wire for the powerpack and grounds it out when you turn the ignition switch off or push the stop switch. Did you clean the connectors, both pins and female receivers, with rubbing alcohol or electrical cleaner before you put them back together? The pulse from the trigger sensor under the flywheel is typically in the .5 volt range so it doesn't take much corrision to affect it.

1983 johnson 35 hp twin cylinder

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