Johnson 150 Wont Idle on Warm Start

[ArtieFishel]

Hello Everyone. First time here. Hoping you guys can help me.

I have twin 2001 Johnson 150's. On a cold start they will start up fine and idle for the 10 minute ride out of the canal. They can cruise all day just fine. The problem comes after i shut them off for any longer than about 15 mins. They will start and run for a couple seconds but they will not idle. The only thing that seems to get them going is to put em in gear very quickly and feather or pump the throttle till they go and keep them above 1,100 RPM. After running they will idle again. It's only on warm starts after it has sat for more than 15 minutes that the problem shows up. It's difficult to try and go to lunch on the water when you cant idle away from the dock. Ive seen others with the same issue but never have seen a

 

[Faztbullet]

Being both motors are doing it I would lean toward the fuel supply side to each motor. It possible they may have carb bowls or vapor separator covers that warp due to heat build up under cowling from setting. Its also possible that its vapor locking since your feathering it till it goes so we are back to heat problem. When was last impeller change?

 

[ArtieFishel]

Impellers were changed 2 weeks ago. The ones i pulled looked brand new.
FWIW, my brother had the exact same issue with the exact same motors (1 model year different) and he never got it figured out. It's a very specific issue under only the circumstances described in my original post.

 

[racerone]

Look at the carburetor bowls.----Possible they are warped.

 

[ArtieFishel]

I have heard of the warped float bowl issue with these motors. I have not checked them that closely. Do you think that would cause this issue only under the circumstances i described? Once i get them started again after running under load for a few minutes they will idle again.

 

[oldboat1]

Since temp. is thought to be related, check the operating temps at the top of the heads -- over 160F is overheating.

 

[Chris1956]

I have the same issue with my '98 Johnny 150. The work-around is two fold. Before stopping the motors, let them idle a couple of minutes to cool off after a high speed run.

When it is time to restart them, advance the throttle and run them at 1200 RPM for a few minutes, in neutral. You should hear them run smooth, and then you can throttle back and run them normally.

Of course I would love a real fix...

 

[JerEazy]

Same thing happened on my 90hp JohnnyRude. And my old 150.

Did the actions noted above (advance throttle in neutral and let it run at like 1200 rpm while we loaded at dock or beach and then pulled back to neutral before leaving).

i finally had had enough with the 90hp and rebuilt the carbs and a light sanding on the bowls to ensure a clean mating (which if I recall correctly we’re plastic and prone to warping). It solved the issue. Can’t say for sure if it was the bowls or something else in the rebuild (carbs were pretty gunky). But it did the trick.