1987 Evinrude 48 Sp has no RPMs

zepper39 · #1 August 19th, 2003, 08:40 PM

I'm new to boating and found this excellent site. I've searched and found many simular posts, but none exactly the same. Repair manual's on order, but checking for obvious problems first.

Motor is 1987 Model E48ESLCUS. Motor starts, idles and runs fine, but only develops 2000 rpm at WOT. Tried primer bulb - bulb was hard and made no difference. Choked and RPMs jumped up to 4000 and ran smooth as long as choke was engaged. Can get another couple of hundred RPMs by feathering choke, but as soon as choke is let off - right back to a steady 2000 RPMs. Noticed by accident that in reverse RPMs would go to 4000 without choking.

Boat had been setting for several months with no fuel. Flushed tank and refilled before starting. Have since checked carbs best I can without removing and found no obvious signs. Checked external fuel filter and screen over fuel pump intake and found no problems. I suspect that the carbs need pulled/cleaned and am waiting on the manual before removing. Did not check the compression (no guage) but motor seems to run o-k when it gets fuel. Did pull the plugs and they were a little on the wet side with a kind of light brown color.

My questions are: Am I on the right track? What else should I be checking? Any help will be greatly appreciated.

ob · #2 August 19th, 2003, 08:51 PM

Boris,Yes ,I think you are on the right track.When you get your manual and begin the carb removal and rekitting or cleaning ,post back if you have further questions and someone will be glad to help.

zepper39 · #3 August 19th, 2003, 09:09 PM

Thanks, OB, I'm sure I will.

One puzzling question that I forgot to ask is why it will run in reverse but not forward? It seems that if there is a problem with the carbs it wouldn't matter whether it was forward or reverse?

Also, I can idle for a period of time and then go to WOT and it will go to about 3000 rpm and act like it's going to run and then just ease right back down to 2000.

Thanks again.

ob · #4 August 19th, 2003, 09:14 PM

Two reasons for the reverse performance.One is that the engine is not subjected to as much load driving the prop in resverse,particularly on thru hub exhaust.Second ,the throttle plate travel is only around half of what the forward gear position is.Symptom sounds like a classic case of fouled carbs.

zepper39 · #5 August 19th, 2003, 09:18 PM

Great. At least it confirms my suspicions. Can't hardly wait for the manual. It'll be a few days, but I'll post back with findings.