96 evinrude 20 2 stroke runs rough in midrange

[Skiptrace]

I have the above engine with electric start. It runs a Little bit rough at idle but not bad, When I open it up slowly, at 1/4 throttle it seems like I lose a cylinder. It stays that way until 1/2 throttle or so then the motor smooths right out, and runs smooth up to WOT. This is consistent it never varies. I just bought this as part of a boat motor trailer package and the prior owner said it ran good, but he did not run it for a year. I do not know him and he is not local. After looking over the motor and talking to other guys it is likely this motor was run but not really maintained. I have replaced the fuel tank, fuel line to the motor, rebuilt the carb, fuel pump, and primer solenoid, changed the plugs . Prior to these being done the motor would stop running and not start when warm, usually at the worst time. That seems to be resolved. None of these changes this symptom. I am learning as I go so please don't assume I know about basic stuff. What I know I learned on the internet or talking to other guys who have different motors.Thanks in advance for your help.

 

[tomhath]

It sounds like the idle adjustment might be set a little too rich. Does the roughness change when you turn it in a bit?

Also, did you measure the oil when you mixed it instead of guessing? Too much or not enough can effect how it runs.

Spark plugs can cause a dead spot too, make sure you have the correct ones for that motor and year.

 

[Skiptrace]

Chief, Thanks for the ideas:

Idle adjustment turned it 1/4 at a time each direction. out 1/2 turn and it smooths at idle, after that it gets rougher again.. not perfect but better and I would be happy with this..

Oil mix I have remixed a new batch previously.and no help. I did not guess. 50 to 1 and I added a conditioner because I cannot get anything but ethanol blend. conditioner also added per instructions.

second set of plugs same thing in the mid range. I bought new champions gapped them according to spec. .

I will take it out on the water tomorrow and see if the idle adjust helps the midrange issue.

 

[oldboat1]

To clean the carb, disassemble and soak. Remove the domed fitting on top before soaking. Clean all openings with a small wire and spray with carb cleaner.

You may be losing spark. Measure spark initially with an adjustable tester (measures ignition strength). If problems at higher rpms, consider attaching a timing gun to see if pulse is lost at some point.

A compression test should routinely be done on a motor that is new to you, along with replacement of the water pump impeller.

 

[Skiptrace]

took it out today started easily idled better, midrange better but not perfect. ran it for 1/2 hour got it warm. shut it off and restarted several times with no issue. ran it slow ran it at 3/4, 1/2 and all seemed better than previously.shut if off after running again for ten minutes. let it sit 20. will not start. choke clicks, motor spins, no pop at all. check primer bulb and it is soft. reprime, I can hear it pushing gas through the motor like it leaked back to the tank or something. Still will not even pop. pulled plugs, fouled, changed plugs ( did not lose any to Davey Jones!) same thing and they are fouled after trying to start. carb throat has fuel sitting in the bottom. trolling motor to the ramp. will not start at all over an hour on the trip back. Last time I was at this point I rebuilt carb, fuel pump amd solenoid. on way home I borrowed a compression tester. 15 pounds in each cylinder. to verify the gauge works I tested my lawnmower and got 60 so it may not be perfect but it works. So back to square one. suggestions?

 

[Bosunsmate]

Find where airleak is in fuel system, you need primer bulb to go hard.
Check to see fuel isnt pouring down motor exhaust from a faulty float/needle
Whens thats ok restart motor, if it doesnt work then that 15 is needing further attention

 

[Skiptrace]

Bosunsmate: your saying that with the motor tilted down after repriming if the float/needle is bad or out of adjustment I will see fuel running out of the exhaust exit at the prop? Only other place I could expect to have the fuel going without seeing it is through o the vacuum and I verified that by removing the hose and repriming several times. The noise I hear when repriming is definitely coming from the fuel pump, but it just may be the fuel being pushed through the pump normally. I am going to relace the fuel lines next although I see no leaks and they look okay to me.

 

[Bosunsmate]

Down the leg and whoosh out the prop or out the front of the carb/air box.
If its not going hard its pumping that fuel somewhere or its sucking air and not pumping really at all, you will get that soft gurgling sound but itl never go hard.
Engine will therefore splutter at times

 

[Skiptrace]

Okay I decided rather than replacing stuff without knowing what was the issue was guessing, SOoooo .I went step by step through the fuel line isolating and think the problem was where the hose connects to the carburetor. Replaced the zip tie with a real hose clamp and tested it, It held solid for three hours. cleaned the plugs and restarted it. ran fine with muffs on. adjusted the idle mixture and got it as smooth as possible. It is turned in 1/2 turn in farther so leaner now. took it out this morning ran it a long time. turning it off and on no problem. Idle is better. still have midrange sounding funny but it seems to work through it at about 1/3 throttle and is smooth from there up. after running it for an hour i shut it off and touched nothing while fishing. ( near the ramp !) 30 minutes. started without choke, shut off and on several times and it settled right to idle each time. Got back to ramp bulb still hard. So I will try the spark tester and another compression tester.

Thanks for your help this really is a great board!

 

[Skiptrace]

Bosunsmate Tomhath & oldboat1: Okay. I have had it out for testing several times. Each time warming it up for 30-45 minutes then sitting for over 1/2 hour and the starting problem seems to be history. The idle is good and top end is fine. the mid range I discussed earlier is EXACTLY the same. I bought a spark tester and in the garage it throws a strong spark on both cylinders. I got a different compression tester and I am at 105-110 on both cylinders so the original tester was not functional. I recorded sound but it definitely sounds funny midrange. This is the link if you are so inclined. midrange 1:00 to 1:15
https://www.dropbox.com/s/1ifx47wyoua6oj6/IMG_0237.MOV?dl=0
So am I being too picky with an old motor?

 

[oldboat1]

If mine, I would take the carb apart -- fully disassemble and soak in lacquer thinner. Finish by running soft wire or monofilament in all openings, then carb spray using the plastic nozzle. Make sure the high speed jet is squeaky clean.

 

[Bosunsmate]

Idles nice and top range sounds good. There is a little less smoothness around mid range, this isnt entirely abnormal, ive heard worse. So yes i think you are being picky, but so am I a lot until i get use to a motor.
It can just be due to the power demands on that boat or even some resonance that makes the boat and motor shake together at a certain rpm.
You could do as oldboat suggests and also make sure your link ad sync is good.
Also look at your sparkplugs in case they illustrate something untoward about it
If it was me id just keep running it as i get over going over carbs very quickly.
Boats also can shake a bit before you get on a plane if the powers not being supplied with sufficient throttle

 

[Skiptrace]

Thank you all. I will do the carbs but after I run it more. Want to do some fishing. Plugs look good when checked. I have four sets and they all do the same thing. Thanks again.

 

[oldboat1]

Maybe just not enough power for your hull -- labors in mid range to get on plane. Might be carrying extra weight -- water under the floor, soaking flotation foam.

 

[Skiptrace]

Oldboat1: 14 foot smokercraft. says max hp is 35. I get a little water in it when running, maybe 1/2 inch in back after being on water for several hours. Not enough to kick in the bilge pump. It dries up pretty quickly. Floor seems solid everywhere. Any way to check that without ripping up the floor?

 

[oldboat1]

Could install a storage compartment or two, and check what's under there in the meantime.