88 Johnson bogging down

[MIScott]

So I've got an Evinrude 140 (87) that sounds like it's doing somewhat the same thing. Already replaced the fuel filter (which definitely helped start-up), and brand new properly gapped plugs (look great after running, not fouled)

Engine runs great under 2200 rpm trolling along, and occasionally it will let me really open it up (was running 33 knots yesterday), but as soon as I pull back throttle (from fast running) the engine will drop down to 2200-2500 rpm and not let me get back up in engine speed. I can NEVER just get on the throttle and get up to speed. (Which I'd like to do because my kids are DYING to go tubing.)

I'm "up north" and not at home so I don't have my usual set of tools, diagnostics, etc. Any EASY tests I can run to see if I can pinpoint the problem?

[THEFERMANATOR]

Sounds like classic early carb issues. Most early OMC's require rejetting to run on the gas we have today. I had to do a rather large jet change to my 86 140 to get it to run correctly in the mid range without it falling on it's face. Unfortunately this is a known issue with the early small bore(85-87) loopers.

[thebottomfish]

Just to check that it's not going into slow mode like mine was...disconnect the temperature sensors that are in each head, electrical tape the wires just in case, run the boat and see if it still keeps you at the low rpm...don't run it for long because you want to know if your motor is overheating
Does your warning buzzer work properly because this would probably dismiss the issue if you don't hear a buzzer

[spareparts]

FYI, 115 and 175 "eagle series" carb bodies are no longer available, carb bowls are. The Looper carb bodies(V$ and V6) are NLA as well. You can still get 90 and 150 "eagle Series" carbs. IF you have an OMC with plastic carbs, take care of them

[bradford]

Originally Posted by spareparts

FYI, 115 and 175 "eagle series" carb bodies are no longer available, carb bowls are. The Looper carb bodies(V$ and V6) are NLA as well. You can still get 90 and 150 "eagle Series" carbs. IF you have an OMC with plastic carbs, take care of them

Good to know Spare. I currently have 4 older Johnny Rudes I'm gonna be selling. Might part out the ones that aren't so pretty.

Also good to see you on, been busy this summer I'll bet.

[spareparts]

slammmed!!!!
had 5 min to spare this morning, then back to fixin boats

[MIScott]

Originally Posted by MIScott

So I've got an Evinrude 140 (87) that sounds like it's doing somewhat the same thing. Already replaced the fuel filter (which definitely helped start-up), and brand new properly gapped plugs (look great after running, not fouled)

Engine runs great under 2200 rpm trolling along, and occasionally it will let me really open it up (was running 33 knots yesterday), but as soon as I pull back throttle (from fast running) the engine will drop down to 2200-2500 rpm and not let me get back up in engine speed. I can NEVER just get on the throttle and get up to speed. (Which I'd like to do because my kids are DYING to go tubing.)

I'm "up north" and not at home so I don't have my usual set of tools, diagnostics, etc. Any EASY tests I can run to see if I can pinpoint the problem?

Finally figured this sucker out.....after replacing ALL the fuel lines, fuel filter, primer bulb AND rebuilding the carbs....still had the issue.

Then I saw a post talking about the temp sensor wires (tan) being routed near or over spark-plug wires possibly causing a false signal. Opened the cover and sure enough, one of them was laying directly across one of the plug wires. I zip-tied the sender wire up out of the way and took her out for a sea-trial last night.

Boat ran flawlessly for the entire time I was out. Fired up immediately, ran great at all speeds, no bogging/hesitation.

Basically the false signal was making the engine think it was overheating putting it into limp mode and preventing engine speeds higher than ~2200 rpm.

SO HAPPY!

[bradford]

Good to know!