Idling issue in the water

[PensacolaJason]

I have been experiencing an issue where my motor (1983 50hp Johnson - J50BELCTA) will not idle in the water but will idle fine on land with muffs on. I got some helpful direction here on the forums to clean/rebuild my carbs as they are likely the cause.

After taking off the intake covers, I found a few odd things. I am missing some pieces on the carb (pictured in red):

#30 - 317476 ? SCREW PLUG, IDLE PASSAGE
#4 - CORE PLUG
#5 - CORE PLUG

The screw plug and washer are completely missing and in place of the two highlighted core plugs someone stuck some kind of brown putty.

My question is if these missing pieces are very important. I plan to replace them once I can get them ordered, but will these missing alter the function of the motor and perhaps cause my issues?

I also compared my carbs with the one pictured below for my motor and the area highlighted below in Blue doesn't appear on my carbs, so I'm not really sure about that. I appreciate any help.

 

[Willyclay]

Re: Idling issue in the water

I suspect the reason behind why it will run on muffs and not in the water is insufficient manifold vacuum created by the back pressure of the water in the exhaust housing when it is submerged. That said, I would find a screw with the proper threads and insert it with a washer in place of part #30 and see how it runs. BTDT and used SS from the local hardware store. You can get an OEM screw & washer from a BRP/Evinrude dealer if you choose. Before you put a new screw in, shoot some carb cleaner in that passage to clean out the jet. You can also use something like weedwacker string as a more positive cleaning method in conjunction with carb cleaner. NOTE: Removing the jet requires a special tool and should not be attempted with a regular screwdriver. The forum can help you with that if you choose that route.

Parts #4 & 5 are designed as removable seals from internal passages/chambers in the carb that probably are part of the idle and/or midrange fuel metering and should be used instead of the putty. IMHO the putty very likely has clogged the passages and should be removed. FYI, these are usually very small openings and getting them clean may be a challenge. Try replacing the screw first and maybe you will get lucky with how the motor runs. Good luck!

 

[PensacolaJason]

Re: Idling issue in the water

Thanks for the reply. What would normally cause insufficient manifold vacuum?

 

[Willyclay]

Re: Idling issue in the water

Because all IC motors are basically air pumps, the amount of air flow is reduced by the back pressure that is absent while running on muffs. With some missing parts & possibly clogged fuel passages in your carb that require good manifold vacuum to draw fuel from the float bowl, I believe that is causing your idle issue. Lots of outboards in poor mechanical condition will actually run quite well on muffs.