Poor Idle Evinrude E50TSLECC

[mturner125]

All, I've been battling with a new to me 50 hp. The motor sat in a garage for many years and has just 150 hours on it. I purchased it from the original owner last year. I realized early on that the fuel lines had deteriorated and had severely blocked up the carburetors. I replaced the lines last year, cleaned up the carbs (several times now), and installed new carb kits. Spark looks to be fine - it's jumping a pretty good gap, and compression is north of 130 on both cylinders. The motor runs fantastic once it gets going - really anything over 1500 rpms and it sings.

I've had the air silencer off for a couple weeks now and it's obvious that the bottom cylinder is missing at idle. Putting my hand up to the throat of top cylinder causes the motor to shut down. RPMs actually increase if I restrict air at the throat on the bottom cylinder. I think its creating more vacuum and causing some fuel to spit out of the high speed jet.

The fact that rpms increase at idle while covering the lower cylinder throat suggests to me that spark is fine at the idle rpm range for the lower cylinder.

I'm positive the idle circuit is clean. I've been through it a few times with with a brush, copper wire (through the pickup and the small idle holes at the top of the carb), and cleaner. I put a very small amount of RTV red at around the copper emulsion tube inside the throat of the carb to block any air leakage. Everything is spotless. I've also inspected the reeds and they look fine with no cracks, chips, or air visible (they're closing). New intake gasket torqued to spec.

I'm away from the boat and can't check this for a few days - Is it possible that I'm getting some air leakage from where the prime hose enters the carb at the top? I didn't recall seeing a compression fitting or a zip tie securing those small fuel lines from the prime solenoid at the carb connection. Could that be the culprit?

If not, any other ideas on what might be happening? Bad lower seal? Is there any way to check that without removing the powrehead?

Thanks in advance

 

[racerone]

RTV does not belong anywhere near a carburetor !----I did not see your work.----So I have to ask.----Is the orifice plug inside the carburetor bowl clean ?

 

[mturner125]

RTV does not belong anywhere near a carburetor !----I did not see your work.----So I have to ask.----Is the orifice plug inside the carburetor bowl clean?

Yeah, the orifice plug inside the carb bowl is perfect. Thoroughly cleaned. I'm a novice so I'd love to hear about other possible things to check out. The motor runs fantastic as soon as I rev up past idle - I can feel the second cylinder come on as I get past 1500-1800 rpms

 

[mturner125]

Hey Folks - I thought I might provide an update. I played around with the small fuel lines from the primer thinking I my have a vacuum leak. That was a dead end. I knew the bottom carb was the problem so I took it off yet again and brought it home. I used acetone to gently clean all surfaces even though they looked perfect. This is the part where it gets interesting - I put the carb under a microscope and inspected the three small holes at the top of the carb (idle jet). I had put a thin copper wire through them many times before. I guess that wasn't enough because even though I could see light through them they looked to be 60% blocked around the perimeter. Still funky. I doubled up on the copper strands and worked them through a bunch of times till they were spotless. The microscope really helped to confirm the crud was gone. Back to the water today and it's holding very strong at idle. We'll see how it goes but I'm optimistic that the battle is nearing the end.

Edit - and now I feel really silly saying in my first post that I'm sure the idle circuit was fine. I was shocked. I held a flashlight to the throat of the carb and I could see three dots of light. I was sure it was fine after passing a single copper strand through it. W/ magnification I could see there was a bunch of crud that still needed to be removed. Anyway, hope this helps folks in the future.

 

[Crosbyman]

thanks for your feedback on the idle chamber drip holes.

I think many are concerned about popping out that little plug let alone peering closely with a microscope/magnifying glass to make 100% certain they are spotless ...something I will certainly look "into" next time I check one.

 

[oldboat1]

I continue to believe that disassembly and soaking in solvent remains the best first step in cleaning a carb -- based on similar experience to that described by the OP.

 

[rowerowe101]

Ultrasonic followed by compressed air is the best method imo.