Johnson 115 dieing out when reurning to idle speed after running

Hi everyone, I hope someone can help I have a 115hp Johnson Fast strike J115GLECM 1998.
I have 2 problems with this motor. When running at 20MPH I feel what seems as though the engine is missing. I checked the inline filter and it is fine no debree. I checked the site glass and saw air bubbles and when I see a bubble this is when the engine sputters. So I replaced the main fuel filer and the pump ball and the hose going from the pump ball to the site glass. No more air bubbles and the problem with the engine missing seems to be fixed.

When I run the motor in the driveway it idles fine and has no issues. When I take it to the lake after running it for 3-4 min or so at about 20MPH and then go to an idle speed while still in gear it will idle for about 1 min and then die out. It is then hard to start. The pump ball still has gas in it and I checked for air leaks via the site glass. No air leaks. Then I ran the boat again at a constant 20MPH and I noticed that the speed would change a little up and down but I am not touching the throttle.

Any ideas?
Is there a way to check the fuel pump?

Re: Johnson 115 dieing out when reurning to idle speed after running

If the primer bulb stays firm, the fuel pump is fine.

When you return the motor to idle after cruising, if you keep the RPM above idle a bit, will the motor stay running? If so, it is likely the carbs are a bit dirty.

Re: Johnson 115 dieing out when reurning to idle speed after running

No it will not stay running, it will die out.
We took the boat out again and ran it a little longer to get the engine hotter and it died out at 2000 RPMs. The engine also starts shaking after it gets hot. The water pump output has a nice stream of water coming out at idle. Just got 3/4 tank fresh gas before when to lake this time.

Re: Johnson 115 dieing out when reurning to idle speed after running

You might disconnect the temp sensors on each head and see if the motor stops shaking and runs smooth. A faulty temp sensor will put the motor into SLOW, where only 1/2 the cylinders are firing. This can causs stalling as well. If that is the problem, you might test the temp sender in a pan on the stove. The sender should ground at about 140*F. If the sender checks out OK, maybe it is time for a water pump rebuild.

BTW- don't leave the temp senders disconnected, since if the motor overheats, damage to the powerhead could be done

Re: Johnson 115 dieing out when reurning to idle speed after running

Did you resolve this issue?? I have the same motor on my boat there is manual primer valve(that red lever behind the intake) that valve should be pointing down...

Re: Johnson 115 dieing out when reurning to idle speed after running

Chris1956 said:

You might disconnect the temp sensors on each head and see if the motor stops shaking and runs smooth. A faulty temp sensor will put the motor into SLOW, where only 1/2 the cylinders are firing. This can causs stalling as well. If that is the problem, you might test the temp sender in a pan on the stove. The sender should ground at about 140*F. If the sender checks out OK, maybe it is time for a water pump rebuild.

BTW- don't leave the temp senders disconnected, since if the motor overheats, damage to the powerhead could be done

Click to expand...

I had my ocean runner go into SLOW mode once.. and id say that it didnt act anything like you suggest. it ran so smooth at idle and up to 2500 rpms, i could not figure it out at first...

just purred like a kitten at idle...i never turned the motor off, because i was affraid it might not start again since it was shaking so bad when i went up to 2500 rpms!!!

if i had shut it off.....then It would have reset the SLOW mode back to normal...because the temps had fallen back down fast once i idles down....

SLOW mode is reset by the temps falling below a certain temp AND the key being turned off...


I think the OP has other issues...could be an initial idel setting...could be a few things,, a few tests and checks need to be done by the OP to figure his issue out i think

bob