Need HELP to get 140 rude running over 3000 rpms? Coil or powerpack?

[clint]

Last week I ran my 1979 140 evinrude, rebuilt in 1998 and it wouldnt plane over 3000 rpm's. I changed head gasket and found it wasnt blown. Reinstalled head and took compression test. Left bank has 125 on both cylinders. Right bank top had 110 and bottom 125. Rebuilt carbs, fuel pump is new, checked all fuel lines. I changed all spark plug wires. I took my 140 evinrude for a ride today. It started out of channel at full normal power of 5500 rpm's, which I havent felt in a long time. Dropped throttle down to 4500 rpms and cruised for 5 minutes temperture was normal. After 5 minutes it dropped down to 3000 and wouldnt go any higher? Got it home and left bank bottom cylinder spark plug was clean as previous run which indicated maybe water getting in cylinder. Now I know that cylinder had to stop firing and fuel cleaned it off when it wasnt firing. At idle in test tank after 10 minutes its a brown normal firing color. Could it be a coil or powerpack? Do powerpacks go bad in just one cylinder and not effect the firing of the other? Could it be just a bad coil after it gets hot, stops giving out voltage? Need all the input, (HELP):'( I can get. Thank You!:%

 

[Walker]

Re: Need HELP to get 140 rude running over 3000 rpms? Coil or powerpack?

You need to do a definitive spark test to be sure its a spark problem, but I have a suggestion. Pull all the coils and inspect for cracks and leaking of filler. Clean the coil ground straps and where they bolt to the block. Swap the suspect coil with another cylinder and see if the clean plug follows the coil.

 

[clint]

Need HELP to get 140 rude running over 3000 rpms? Coil or powerpack?

I will do that check tomorrow. This problem has been haunting me. I dont want to take this problem to a marina after doing all this work on the engine in the last 2 weeks. Switching coils sounds like I will find it deffinatly. Only problem at idle it doesnt show it not firing. I will have to put it under load in the water. Powerpack would affect the top cylinder too if it was bad? Thanks again Commander! You have been so Helpful!

 

[Walker]

Re: Need HELP to get 140 rude running over 3000 rpms? Coil or powerpack?

Usually when you lose only one cylinder under a load its not the powerpack. Its usually a coil, high tension lead, or a bad ground.

 

[KYHunter2]

Re: Need HELP to get 140 rude running over 3000 rpms? Coil or powerpack?

Clint, while your checking all the grounds, heres a little tip.

The engine grounds , as well as coil grounds, (area where coil meets head), and any other exposed connections.

Like solenoid , starter , etc.

After cleaning, 2-3 coats of 3-M, liquid elect. tape.

Will keep them dry and protected for a good long while.

I recently , removed some on a motor, I used it on 3 years ago.

And after peeling it off, the nuts, bolts, etc. were shiney as new.

KYHunter

 

[clint]

Need HELP to get 140 rude running over 3000 rpms? Coil or powerpack?

I replaced the coil and cleaned all my grounds as informed. Started it up in test tank with engine running strong. Thursday will drop boat in water for test run. I will be back to follow up here in the forum on results. I notice most postings arent finalized with results of the problems being fixed. I will be back. Thank You Everyone! 8)

 

[clint]

140 Rude finally running normal at 5500 rpms check out why I had no spark in on

140 Rude finally running normal at 5500 rpms check out why I had no spark in on

8) My 140 Evinrude is finally is back to normal at 5500 rpm's. Here is what I found out today. It took off fast and planed out beautifully, went right up to 5500. I dropped it down to 4500 and ran it light and steady. Only problem was when I throttled back down I felt engine miss a low rpm and idle. Took off again and it planed out to 4500-5500 and ran it at 4500 for a hour. Ran it again at low rpm and it was missing again. Then it just wouldnt go over 3000. It was locked at 2500-3000 rpm's and that was it. Back to the drawing board. The last few minutes to the ramp to take the boat out of the water, my son & I was grabbing the last of the crabs with a net off the high tide mark and I put my hand on cowl cover which was wet and damp from the run and I felt a jolt, shock? When I got boat home, I found bottom spark plug wire boot was indented from the cowl cover inside bolt from the lock down lever, grounding out #4 cylinder which was missing in the past. Never with cowl cover off in test tank or with muffs. I assume today and in the past when engine got to operating temperture the rubber got soft on the spark plug boot and grounded out to the bolt. The bottom of cowl cover has rubber boots which on the #4 cylinder side it was ripped up and made a goo ground right to bottom of cover and directly to the engine ground. Also what makes it worse is my cowl cover seal needs replacement. So the mystery is solved after I changed plugs, spark plug wires, re-built carbs, replaced fuel pump, changed the head gasket. I want to thank all of you for writing back to me and helping me pinpoint what was going on. Thanks so much to all the pros on this site! 8)