Midrange Issues

Randy000

Seaman
Joined
Oct 7, 2012
Messages
57
Hey I have a 97 Evinrude 130. Two weeks ago my engine starting shaking at 2400-3000 rpm ( noticed it after hitting another boats wake a little hard. I took it out the other day and it ran fine at idle up to 2400 rpm, and fine over 3000 rpm.
I can cruise at 2200 rpm and it seems fine, as soon as I go over that it starts to shake. Without touching the throttle RPM would increase to 3000 for a few moments, then back down to 2400 for a few moments etc. Powering about that I could bring the throttle up some, engine increases to 3000 rpm, a moment later its increasing itself up over 4000 and runs fine.
I checked the plugs they arent fouled, only one looked pretty wet. The intermediate orfice on the carbs are right there when you pop off the silencer, so I looked at those and they weren't blocked. Checked the fuel for water, filter was clean.

Does it sound like I'm losing a cylinder?

Thanks for any help!
 

fireman57

Captain
Joined
Aug 24, 2004
Messages
3,811
Re: Midrange Issues

It does sound like that if you are sure that your midrange jets are totally clear. You might want to run a small wire through them to make sure. Take a timing light and a buddy with you next time and when it does this check for spark.
 

Randy000

Seaman
Joined
Oct 7, 2012
Messages
57
Re: Midrange Issues

Yea the jets are clear with a decent size hole. I didnt pull the small plate of the side of the carb that has the passage for that jet yet. Thought about throwing some new plugs in it incase hitting the wave cracked one. Going to check the spark to see if I possibly cracked a coil or something.
 

Randy000

Seaman
Joined
Oct 7, 2012
Messages
57
Re: Midrange Issues

Checked all cylinders with a timing light...all seem to have ignition. Any other ideas?
 

Randy000

Seaman
Joined
Oct 7, 2012
Messages
57
Re: Midrange Issues

On muffs its running fine at idle but bring it up into the 2000's in RPM and its all over the place in RPM.
 

fireman57

Captain
Joined
Aug 24, 2004
Messages
3,811
Re: Midrange Issues

Don't run it on muffs over 200rpm or you can get what is called thermal runaway. The engine needs back pressure and if it doesn't have it will take off and over rev. You won't even be able to shut it off with the key. You need to check the spark with a timing light when it is under a load which means you have to have it in the water and test it under the conditions that it acts up in. this is why the shops charge what they do because it has to be tested. They use what the call a test wheel to simulate these conditions on muffs but it works pretty well. I don't think you want to spend the money on a test wheel though.
 

Randy000

Seaman
Joined
Oct 7, 2012
Messages
57
Re: Midrange Issues

I eventually put the motor in a tank of water. But before that I could simulate the issue and while it was acting up I tested the ignition with a timing light and checked the spark with a gap tester. Both looked fine. If the power pack or timer base is the issue do they have the tendency to vary the timing causing my issue?
 

fireman57

Captain
Joined
Aug 24, 2004
Messages
3,811
Re: Midrange Issues

If the time base sticks it could cause this. Make sure that it moves easily.
 

Randy000

Seaman
Joined
Oct 7, 2012
Messages
57
Re: Midrange Issues

Yea it moves freely. A friend of mine was saying the this engine has magnets under the flywheel and they are notorious for moving. Sound right?
 

fireman57

Captain
Joined
Aug 24, 2004
Messages
3,811
Re: Midrange Issues

They can come loose but it's not a real common occurence but it wouldn't hurt to pull the flywheel and check. It doesn't make sense that they wouldn't "shake" at all rpm's though.
 

Randy000

Seaman
Joined
Oct 7, 2012
Messages
57
Re: Midrange Issues

Does pulling the flywheel require a puller or just a big socket for the nut?
 
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