Late 90s Evinrude 50 Lower Cylinder Not Firing at Idle

[mturner125]

I could use some advice on my next step. I purchased the engine 2 months ago and at the tine it has about 140 hours on it. It took me a couple trips out to realize the fuel lines had gone bad and were filling the carbs with crud. They were absolutely filthy with fuel line material. I’ve been over them a couple times and the engine performs fantastic at 2000 rpms plus. Idle has been a problem- it settles in at a rough sounding 650/700 rpms.

Yesterday before putting the boat on the trailer I decided to pull the spark plug wires one by one. Pulled the top and it immediately shut down. Pulled the second and there was no change in the idle. It kept running.

couple observations- when I got the motor I noticed there was a bit of rust on the lower spark plug. Does that point to water intrusion? Reeds look great from the outside. Would putting an endoscope in the spark plug holes show if the gasket failed? Perhaps a much cleaner piston than the other? Think this is still a carb issue? Fuel pump is new and so are the lines. Tank was cleaned and I have 2 filters in line.

thanks In advance for any advice

 

[racerone]

Perhaps it is an issue with lower crankshaft seal.----Compression test must be done as well.---Post the numbers.

 

[mturner125]

Compression was checked after warm up last week. Both cylinders are in the upper 120s. Thanks for the tip on the crankshaft seal.

 

[mturner125]

What should I be looking for to determine if the lower seal is bad? Oil/fuel mix in the lower portion of the cowling?

 

[tblshur]

did you remove the little round plugs in thecarbs and clean that is your idle circuit also i would get a adjustable gap spark checker and check for 7/16 in spark on the lower cylinder goodluck

 

[mturner125]

I’m almost embarrassed to say how many times I’ve been through the carbs. Pulled the plug and then backed out the high speed brass orifice. Took a copper wire to clean the emulsion tube that sends gas to the idle circuit up top. Cleaned the needle and seat. Cleaned all the small passages with nylon brush, copper wire (small openings), carb cleaner and compressed air. Set the float to spec per manual. Verified the air orifice up top is good as well as the priming circuit. I went over the emulsion/pick up tube one more time yesterday and I’m going to test it tomorrow.

i can’t stress how bad the carbs were when I first got it. The fuel lines were putting out these really nasty black chunks. The high speed orifices were completely clogged and I had to scrape a 1/16” layer of garbage out of each bowl. They look spotless now but it’s possible the interior of the idle circuit pickup was less than perfect. I had put carb cleaner and air though them multiple times already but not much in the way of scraping (copper wire).

I have checked spark. Tester is showing it’s jumping the 7/16 gap.

Thanks for the comment. I’ll report back

 

[juno pierrat]

well then, spray some premix in the lower carb and tell us what happens