87 Evinrude 48SPL erratic idle and dying

[greasemonkeyjm]

I have a 87 48SPL model E48ESLCUS iI bought llast Week on a pontoon boat.It has been sitting since the first of the year, anything before that I'm unsure of. Engine has 125 pounds compression on each cylinder, spark on both will jump across 7/16 gap.I'm running 50:1 mix, has the non adjustable carbs, it starts fine, but tries to die if you let it sit at idle,and when you put it in gear, you have to go ahead and throttle up a little to keep it running but after you come up from idle it throttles to WOT smoothly with no stuttering or hesitation, but at idle the rpm will run up and down, it doesnt have a tach, but i would say idle is around 650 or so, but it climbs as high as 3,000 rpm's, high enough that i quickly shut it down to keep from slinging it apart. I know that a linc and sync may would help the dying when coming off of idle but I don't see where that would have an effect on the erratic idle speeds I tore into the carbs and they look clean, but I have them soaking as we speak. spark plugs has a good color to them and just a touch of wetness after the engine has set for about 1.5 hours after a run.


thanks
Bo

 

[bonz_d]

Finish your cleaning and pay especially close attention to the slow speed circuit in the carb. That would be the small tube inside the larger center pick up tube. Also use a can of spray cleaner and spray those pick up tubes really hard. Then use a can on compressed air like one would use to clean a keyboard and blow out those tubes. Reassemble and see what happens. My guess is everything will be good.

 

[bonz_d]

Also maybe check all the hoses and trim off the ends to ensure a tight solid fit.

 

[greasemonkeyjm]

Thanks for the response, I went thru everything really well and found no blockage at all, reassembled and still have the same rough idle results and it will sometimes just die completely, but it will normaly fire right back up pretty easy. I went and bought some fresh gas because i was unsure of the age on the fuel that was in it. I did notice that it seems to be running stronger on the top cylinder than the bottom, with both carb butterflies shut completely I can start it with one plug wire off at a time, and the top cylinder will run smoother and at a higher RPM than the bottom.

 

[greasemonkeyjm]

o.k. status update, I installed new QL78YC champion plugs gapped at .30, with no change in how it runs, but I did notice that with it running, I can put my hand across the Carb Throats and the top carb and cylinder has quite a bit more suction thatn the botton cylinder, which would coincide with the upper cylinder seeming to be running stronger. Any ideas on what would be the cause of the suction difference, especially since the commpression was even on both cylinders when it was checked 3 days ago

 

[bonz_d]

Would just be guessing but maybe look at the leaf plate on that cylinder. Could be one or more are not closing and sealing properly.

 

[greasemonkeyjm]

I pulled the plates and visually didnt see any rust or chips or damage, other than that, is there any visible things to look for ? Thanks

 

[racerone]

Inspect bottom crankshaft seal ??-----You may be losing some crankcase compression.

 

[greasemonkeyjm]

Thanks again for the replies, I was sure thinking it may be the Reeds, but just my luck, the bottom seal would be the only other thing I can really think of that could be doing it, I could see the idle circuit being stopped up causing it to idle too low or not at all, but since it dies out and also races up, I can maybe see an air leak somewhere. other than being torn, how can I tell if the bottom seal is leaking after I get the powerhead off ?
thanks