Johnson 140 bogging down

[vandy21]

Hey guys, haven't posted in a while, but I have a question now. I have a 1988 Johnson 140 and it does not seem to want to run at WOT. The engine has run great in the past at any speed, but now it boggs down getting up on plane, and then once I'm on plane I have to slow it down to around 3500-4000rpms. I know this is a better cruising speed than WOT anyway, but I still would like to be able to run WOT sometimes. I'm thinking it may be carb/gas related? I just run regular gas station gas through it (not a lot of boat fuel options around here) and I know the ethanol kills these engines. I always run sta-bil or ethanol treatment when I fill up and that seems to help with the bogging down issue. Any suggestions?

 

[jtexas]

Re: Johnson 140 bogging down

From the information you provided, we can narrow it down to three possible causes: compression, spark or fuel.
It's actually a classic symptom of clogged carbs, but you'll want to do a compression and spark test first, to rule those out.

Best not to run it like that; any cylinder starved for fuel is also not getting any lubrication.

Far as I know, that motor was designed to run on 87 octane. Raising the octane level makes gas harder to ignite, so it can be run in engines with high compression ratios. The added compression and advanced spark timing more than make up for the lower energy content of the fuel.

Stabil is still a good idea.