Idle issues on my Johnson 112 SPL

[Scubaslife]

I rebuilt the power head on my 94 Johnson 112 SPL and I'm having trouble getting it to idle properly. It will run out well and cruise well but won't hold idle more than 1 or 2 seconds. However, if I tilt the motor up it will idle for about 30 seconds but eventually die. I took apart the carburetors and cleaned them VERY thoroughly with Seafoam carb cleaner but I didn't rebuild them. Beginning to think I need to order a carb kit and rebuild them but didn't want to do it if there's another easier explanation that I've missed. Any thoughts?
Things I've already done...
Replaced check valves
Replaced primer ball
Replaced fuel pump
Replaced plugs
Replaced plug wires
Cleaned carbs (but didn't rebuild)


Thanks
Scuba

 

[Joe Reeves]

Re: Idle issues on my Johnson 112 SPL

Sounds like when tilted, the engine is running lean at idle.

I assume you know which jet on the carburetors is the idle jet... if not, check your manual.

The jets are idle air bleed jets, meaning they meter air, not fuel... smaller size jet = richer fuel mixture.

There is a small number embedded in the face of those jets (example 29 = .029).

Whatever size those jets are, downsize them to the next lower size. I don't know if this will cure your problem but it's the route I'd attempt.

 

[Scubaslife]

Re: Idle issues on my Johnson 112 SPL

Sounds like when tilted, the engine is running lean at idle.

I assume you know which jet on the carburetors is the idle jet... if not, check your manual.

The jets are idle air bleed jets, meaning they meter air, not fuel... smaller size jet = richer fuel mixture.

There is a small number embedded in the face of those jets (example 29 = .029).

Whatever size those jets are, downsize them to the next lower size. I don't know if this will cure your problem but it's the route I'd attempt.

Hey Joe,
Thanks for the info. Sounds like you're recommending I change out the idle jets, correct? I'm curious... They're the same jets that were on the motor prior to the rebuild, would the rebuild somehow cause them to foul or need changing?
Thanks,
Scuba

 

[Joe Reeves]

Re: Idle issues on my Johnson 112 SPL

Hey Joe, Thanks for the info. Sounds like you're recommending I change out the idle jets, correct? I'm curious... They're the same jets that were on the motor prior to the rebuild, would the rebuild somehow cause them to foul or need changing? Thanks, Scuba

If the engine idled perfectly with the present idle air bleed jets when tilted before it was rebuilt, the same jets should function in the same manner.

However, after once again reading your original post closely, you don't say why the powerhead was rebuilt originally... overheated, ignition failure, pre-ignition, fouled carburetors, whatever, but the most common cause of a powerhead failure is due to fouled, clogged, gummed carburetors which result in a lean mixture in which case the carburetors should have been completely dismantled, cleaned thoroughly, and rebuilt with complete carburetor kits.

A powerhead does not fail by itself, something caused the failure. Do you know what it was?

Double check the compression and spark, and if you find that both are as they should be, to contradict my original reply, before changing jets, I would suggest double checking the sealing areas of the carburetors, intake manifold, etc, and cleaning and rebuilding the carburetors.

 

[Scubaslife]

Re: Idle issues on my Johnson 112 SPL

Joe,
Thanks again for your help.
To answer your question, I blew a ring on piston #3 and figured since the motor is nearly 20 years old (I've only owned it about 3 years) & since I was going to have to break down the head to replace the piston & rings anyway, I might as well rebuild it. That way I knew how it was built and how many hours were on it.
Now that it's rebuilt I'm having a difficult time getting it to idle. I think I need to go ahead and rebuild the carbs but I didn't want to do it if there was something small I was missing. That said, I was testing the primer solenoid and it doesn't seem to be working properly. At least not according to the repair manual test. I'm wondering if that would cause it not to idle. It wouldn't explain why it would idle while tilted though...
Any thoughts?
Scuba

 

[Scubaslife]

Re: Idle issues on my Johnson 112 SPL

Well, I pulled off the primer solenoid and opened it up and as suspected it was toast. The center pin melted into the cylinder and springs and froze it completely shut. I ordered a new one, should be in next week. I'll let you know if it fixes the problem.
Thanks,
Scuba

 

[Scubaslife]

Re: Idle issues on my Johnson 112 SPL

As a final follow up...
I replaced the primer solenoid and rebuilt the carbs completely and the 112 is running beautifully! Thanks for the input.
Scuba