70HP Johnson 3 Cylinder 2 Stroke Bogs Down

JYD33

Recruit
Joined
Sep 10, 2024
Messages
1
I have a 1996 Johnson 70hp 3 cylinder 2 stroke outboard motor that bogs down under full power. It ran great last summer but the first trip out this year it started bogging down, sounding like it's flooded or fuel lines are blocked, once I went full throttle. At first it was almost immediate after pulling past the no wake zone. With the repairs done below, it took about 5-10 seconds and the last outing (see video link below) it lasted nearly 30 seconds. I need ideas of what else to test or replace. Mechanic doesn't have a tank that allows him to run it full throttle so it has been, fix this, take it to the lake and test it. We have done this 3 times and I'm taking it back for a 4th time because the problem isn't fixed. I'm hoping for some insight and suggestions.
Here is what he has done thus far:
Compression is good
Replaced power pack
Getting spark
Rebuilt carbs
Replaced fuel pump
Replaced fuel lines
Here's a video link of what it's doing.

Thanks in advance. - JYD33
 

saltchuckmatt

Commander
Joined
Jul 19, 2019
Messages
2,639
If the alarms test ok I'm thinking the diode in the harness went bad. Others will come that will know more but limp mode seems to be coming on. The oil tank has to match the tach so other issues can happen.

Post model number.
 

racerone

Supreme Mariner
Joined
Dec 28, 2013
Messages
37,816
" Good compression " means nothing to me , post the actual values.----Run with a timing light one cylinder at a time.----Might help determine if spark is lost on 1 cylinder.----Remove cover in front of carburetors.----Shine a STRONG flashlight into each carburetor bore.----Compare amount of fuel coming up each nozzle when motor falters.----What size boat ?----What pitch prop?----Motor is not revving up to near its potential !
 

saltchuckmatt

Commander
Joined
Jul 19, 2019
Messages
2,639
I agree, when motor was running faster it was not full bore. Was the throttle handle all the way up?
 
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