1987 Evinrude misfiring?

[green head]

I have a 1987 20hp Evinrude that misfires. At least I think it is misfiring. It doesn't happen all the time, it can go weeks without having this problem but I caught it on video this time. Also when it is happening it will be more pronounced when the engine has been running for a while. Here is the video link https://youtu.be/5SSmcnzCE94 In the video you can hear a surge and see the engine move a bit. Any help with a diagnosis or a fix would be greatly appreciated.

 

[Jasmc79]

Make sure you have spark coming from all of your spark plugs, do a compression test on all cylinders

 

[racerone]

open the low speed mixture 1/4 turn and note the results.

 

[green head]

No Title

I tested the spark plugs and compression. It had good spark and compression was 80# on the upper and 78# on the lower. I've heard 100 is ballpark. Don't know if those numbers are good enough. I adjusted the black knob on the upper portion of the carb but not sure if that is the low speed mixture or the high speed mixture. See attached picture to see what I adjusted. Problem persists

Also I followed the fuel line looking for problems and found the pickup line in my fuel tank was loose and was sucking up air too. Replaced the faulty hose although that did not fix the problem either.

 

[jakedaawg]

Thats alwful low compression. I would try a different gauge be fore you go further. It does start so I am guessing the guage is wrong, was it from harbor freight or a really cheap one?

 

[green head]

It was a brand new one from harbor freight. What should the compression be?

Problem is only noticeable below 3/4 power. Above 3/4 power to full it seems to run fine.

 

[jakedaawg]

Rent a real gauge from a parts store. You probably have decent compression but its worth knowing before you go further. If it really is in the 80's you will never get it to run well. The ones from HF are junk and have led several astray.

 

[green head]

No Title

Ok I did some trouble shooting today. I put some new spark plugs in, no change. Checked the fuel for water, no water. I borrowed a compression tester from O'Reilly's. Not sure if the results are anymore accurate. It was a Evertough brand and while not hooked up and the pressure relieved it read 30 psi. When running the compression test on both the upper and lower I got 150 psi.

The motor started to run worse also and is very reminiscent of a problem I had in 2010 with it. I took it into a shop then and they cleaned the carb and found chunks of rubber from the fuel line. He said the ethanol had been breaking it down. They had to replace the entire fuel system. $1000 project. I don't want to drop that much money again. I checked the fuel filter screen on the fuel pump and didn't see any rubber bits. I tried spraying some carb cleaner in the running motor and it did not improve. My next guess is to remove the carb and do a cleaning. But I don't know how to get it off. The starter is in the way of one of the carb nuts and I'm not sure how to get the starter off. Pics attached if you have any guesses let me know.

Let me know if you think I am heading down the right road or the wrong one.

Thanks

 

[racerone]

Well----$1000 to replace the entire fuel system ???-----That is sad a shop would do that to an owner.--And spraying cleaner into a carburetor does nothing as it does not reach the metering jets !---With the control in the idle position post a picture.-A picture of the adjustable stop on that long rod that goes from carburetor to the back of the motor.

 

[jakedaawg]

Okay, I just watched the video. That isn't exactly a misfire, it is called a lean pop or lean sneeze.

I could replace the entire fuel system for a few of those, including new tanks and labor at my shop for a grand! Find a new shop or let the people here talk you through it.

The pic racer asks for will be helpful. Start there.

It can be a little tricky to remove that carb if you haven't done it before. There are several fasteners that need to be removed and one is fairly hidden. Look at a parts blow-up diagram and it helps. You can find one at BRP's website. Also be careful when removing the wire terminals as on the older motors you can damge the wires that are corroded under the insulation. New engine side harness is not available any more to my knowledge ( I know because I need one myself).

 

[green head]

No Title

Sorry I haven't got back quickly. My boat is an hour away from where I live. Attached are a couple pictures of the adjustable stop in the idle position.

Also here are a couple more videos of the motor running. The first one is after I got it started it ran fairly well right away. https://www.youtube.com/watch?v=VFnj_riyEn0 The second one is after the motor was warmed up and you can see it "sneezing" a lot. https://www.youtube.com/watch?v=jq5EDBm4aaU

 

[Chinewalker]

That is not a fuel issue. That is an ignition issue. I would hazard a guess that if you pulled one of the plug wires while it was running (with an insulated pair of pliers) you would likely stall the motor on one, but not the other.

 

[flyingscott]

chinewalker is right That acts and sounds like an ignition issue. It looks like a failing powerpak or coil. Your best bet for a compression test is find an auto mechanic pay him 20 bucks to do it. The problem with rental compression testers is they get abused where an auto mechanic will have a Snap On unit and they take care of there tools. Find the cylinder that is misfiring like chinewalker said and swap the coils see if the problem follows it.

 

[green head]

I will try and drive out to my boat tomorrow and troubleshoot as chinewalker instructed. To swap the coils will I have to remove the flywheel?

In 2011 I had a complete electrical failure, no elec start and no spark. I took it to a shop and they replaced the power pak. In 2013 the elec start stopped working and I replaced the power pak to see if that would fix it. It did fix it. The shop put on a CDI power pak. I put on a Sierra power pak. If this is a bad power pak, am I installing crappy power paks or could there be something causing them the fail.

 

[flyingscott]

The coils should be mounted on the side of the motor they are attached to the spark plug wires. When you swap the coils make sure you swap all the wires do not just move the coils all the wires are cyl specific. your powerpaks should have warranties on them.

 

[sutor623]

You are absolutely right about there being a reason that these powerpacks have all blown in such short time. Main cause of that is voltage coming in from the kill circuit. The black/yellow wire that goes to the powerpack should not have any voltage at the leads. Unhook the blk/ylw wire from the powerpack and run one end of the multimeter to gnd, the other tothe blk/ylw wire (from boat side)and check for voltage. If you have voltage there thenyouhabe found the source of your powerpack failures.

 

[green head]

PROBLEM SOLVED!!!

I went out to my boat and tested the black and yellow wire with the ground to see if there was voltage and there was none. I then fired up the motor and pulled the top spark plug wire and the motor quit. I then fired it up again and pulled the bottom spark plug wire and the motor continued running rough as it had been doing. I shut it down and proceeded to take off the lower coil and as I was the wire from the power pak just came off. I had tested all the wires earlier by pressing on them all but not seeing how firm they were attached. This wire was very loosely attached to the coil. So I reattached the coil to the motor and slightly crimped the attachment for the power pak wire so it was snuggly attached to the coil. I fired up the motor and it ran great. Took it out for several test drives progressively longer and further from the dock. Thanks for all the help!!! I learned some new skills and learned more about my motor.

 

[David Young]

Just wondering.....What is your top speed now?

 

[green head]

Sorry don't have a speedometer on my boat. But the top speed feels the same as it was prior to my problem