1998 Johnson 50 hp still dies at low idle

[skoboten2day]

Just about had it with this outboard. Probably less than 200 hours total on this motor. Bought it from my dad after it sat for 6+ years. He took good care of it and I never remember it being so temperamental. Spent hundreds of dollars with a highly recommended mechanic rebuilding carbs, replacing water pump, spark plugs, and disabling VRO so it runs on pre-mix 50:1. The boat runs great in the driveway on ear muffs and a hose. I buy high quality oil and non-ethanol gas. I will launch it and let it warm up for 10 minutes or so before I leave the dock. It runs great 1500 - 5000 rpm's. I'll run it for over an hour, but as soon as I throttle down to idle speed, it cuts out. It cuts out in gear and neutral. It's actually less temperamental cold than after running for an hour or so which makes no sense. I took it back to the mechanic and he said he didn't notice what I was talking about but said he cleaned the carbs again. Still dies at low idle like when you're coming in to a dock or lining it up on a trailer. Why in the world would it run better out of water and colder than in the water and heated up? Thoughts? Thanks

 

[oldboat1]

Check the temp when the motor is run hard out on the water. The top of the head should be around 140F or so, never over 160F (160 is hot enough to burn your hand). And in any case, 20 yr. old ignition parts can act up when they heat up under load, unlike on the hose with no back pressure. (CDI electronics has some detailed testing instructions online. Replacing parts is very expensive, as is diagnostics in a shop.)

You can check spark when it wants to stall — use a timing gun on each of the plug wires to see if the ignition isn’t putting out on one or both. You won’t know what is causing the no-spark condition, but it’s a beginning.

You can tweak the air mix needle slightly richer to see if that stops stalling. You can also set the throttle idle speed a little higher to see if that solves the problem. If you reset the throttle idle, first remove the remote cable. Adjust the cable and reattach it to match the new idle setting.