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70hp 2001 Johnson Engine stalls under load

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aspaziani

New member
Hello everyone,

I have a 70HP Johnson outboard (J70VLSIS) that i rebuild the carbs on this year. Last year i noticed it would hesitate under load and at times open up for a few seconds before bogging back down, it would also die while idling towards the end of the season. after rebuilding all 3 carbs and adjusting the air fuel mixtures screws i was able to get it to idle pretty nicely. I put it in the water this weekend, and it almost immediately dies when i put it in gear and give it some gas. I was able to finally get it up and running and i managed to get it to WOT, but it would surge on and off, after i finally slowed down it eventually died. I had trouble starting it back up after it cooled down but i was able to attribute that to the primer since i was able to start it right up if i flipped the red lever and manually injected fuel. The way home (about 1 mile) it ran great, once i got to the no wake zone and started to slow down it died again. Seems to be a problem on the high end but i could use some guidance as to wear to start my adjustments. Let me know what other info could be useful. im going to test the primer this weekend, but i don't think that's related to the issues when its under load.
 
The primer is an electric valve.-----When key is pushed in , it opens.-----With motor cranking fuel is injected into the engine.-----This fuel bypasses the metering circuits on the carburetors.------Is oil injection in service ?----Best post the results of a compression test first.
 
The primer is only used for starting.-----Does spark jump a gap of 7/16" or more on all leads ?-----Water in the fuel ?------Test run with another tank and hose.
 
its brand new fuel and line, new plugs. Just to be clear, the engine does not have a problem starting when i override the primer. I assume its either busted or not attached correctly, maybe a loose wire. What im more concerned about is the fact the engine dies when its in gear and i give it gas. I was able to get it to WOT after some babying but its surging and not reliable, then dies when it slow down to idle.
 
Good Morning everyone,

I have an update to this case. i took the carbs off and blew them out again, replaced the carb and the air intake gaskets. I put it all back together and took it out, it ran great! i was able to shift back and forth and throttle it up and down. I got it out to the open water and opened it up and it ran perfect, lots of power, no surging. After about 5 minutes at WOT, almost like a switch flipped it dropped down to about 3/4 throttle, didn't slowly go down or shudder in any way, it was as if i lowered the throttle by hand. I throttled it down to idle and it died. I was finally able to get it started again, but now i could not give it any gas in gear above shifting. I was able to crawl home but i couldnt give it any gas the entire way. Thoughts?
 
another update, i thought it might be the thermostat since it dropped down so suddenly after running so well. I replaced the thermostat and no change. I was able to run it for about 2 minutes giving it gas, but after that it died again. It didn't even have time to get hot. I even tried running with the temp sensor disconnected.
 
Sorry----An outboard like yours can overheat in less than 1 minute at full throttle.-----Have you looked at the water pump impeller , yes or no ?
 
i did the impeller last year, i have plenty of water coming out the tell-tale, when i ran it the other day after i replaced the thermostat i never got it to full throttle, i was reversing out of my slip. After i got about 50ft it bogged down and died.

almost seems as if the carbs are over filling with fuel. After i pulled them it ran great for a total of about 30m then died. after it sat for about 2 weeks it ran great for about 2m then died. but it always starts up and idles fine, it will run in gear at idle but nothing above that.
 
Last edited:
aspaziani said:
Another piece if information that might be helpful, i am able to throttle it up no problem when its not in gear.
Click to expand...
Means nothing and stop doing that. Have you checked for spark? Is the roller on the carbs still in one piece? Did you link and sync the carbs?
 
At full throttle... and holding it there, assuming you have a built in tank, the fuel in the tank pretty much stays put in one area... not sloshing around.

Re-check the carburetors and the fuel line(s) for water.
 
i have not checked for spark, but i did (from the advise of another mechanic) close off the air intake to each carb one at a time to see if it made any difference, each time i did so the engine started to die, so i can assume each cylinder is firing. yes the roller is still in once piece. Per the manual the only sync setting to make is to be sure the choke plates are all closing at the same time. There is no port to attach a vacuum gauge.
 
I have the same
Issues with the same motor did coil packs lines drained the tank new fuel lines cleaned carbs new vro pump new impeller new air gasket new spark plugs! Help
 
Oof man, that sounds way too familiar — had almost the same thing happen last summer with my old Evinrude. Thought it was the carbs too but turned out my fuel vent was clogged and messing everything up once it built pressure.
Also random side note — if it gets to the point where you're just fed up, renting a boat for a weekend is honestly a vibe 😅 I took a break and booked through 12knots for a chill weekend and it kinda brought the fun back. Not saying ditch the motor, but yeah… sanity check lol.
 
Compression is great! Hoping it is the stator! It ran great 7 times I brought
It out this year and back again to square one I’m sick! Replaced gas lines twice, drained tank.. new spark plugs.. new coil packs and wires.. new exhaust gasket.. new vro new water pump impeller. Had carbs cleaned twice. Won’t go over 3000rpm then when going slow to dock or neutral it dies but starts right back up! I’ve dumped a ton of money into this mother j70plssd! I don’t give up easy And also don’t have money for a new motor! Again it rain great 7 times this year and then starting acting up again. Stator tested shitty today so I ordered one another $400 fml! 🤦‍♀️ anyone have an ideas
 
Replacing parts without testing gets expensive.-----Eventually you will solve it.----Don't throw out any parts as you might save them for spares.
 
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