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92 Evinrude 15 HP bogging down

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  • 92 Evinrude 15 HP bogging down

    Hi All,

    New to the forums here, looked around a bit and this seemed like a perfect place to ask!

    I have a 1992 15 hp Evinrude that I purchased last fall. I've been having issues with it bogging down under load, but it happens sporadically. It's happened several times now where I launch, I run upriver for about a half hour with WOT and it runs fantastic. I usually fish for awhile, and while running back down, the engine starts to bog down under WOT. If i back the throttle off the motor stops bogging down, but when I increase throttle again, it bogs once more. Sometimes it dies at this point if I keep the throttle going, and sometimes I can back it off so it just idles. If i shut off the engine and let it sit for about a minute or two, I can restart and get another five min of good running at WOT or so before the whole process repeats itself. Priming the fuel bulb while its bogging downg (sometimes) helps and RPMs increase. (and sometimes doesn't).

    I know some basics about 2 strokes, and this is a list of what I've done to the motor so far in order of how I've done them.

    -New fuel lines/primer bulb/fittings
    -Put new ethanol free gas in tank w/ 50:1 oil mix
    -Compression test. Both cylinders at 125/127
    -new spark plugs
    -spark test. Jumps gap correctly.
    -New fuel pump
    -Pulled off the carb and did a complete teardown and cleaned all fittings and jets and put new seals in it
    -Did a "lync and sync" to adjust timing of butterflies on the carb in relation to throttle
    -Adjusted fuel/air mixture and adjusted idle speed to optimum.

    So as you can see, I've tried a few things, but am still having the same issue. I should mention that so far since owning this outboard, I've only run it in cold water (32-35 deg) since I live in MI. Not sure if this plays into it at all, but I am curious to see what happens when the weather/water warms up.

    Is there anything I'm missing here or any thing else I could try? Anything obvious that I may have missed?

    Thanks in advance!

  • #2

    should get an adjustable spark tester to measure spark. Should see something close to a half inch (remove both plugs for testing). Do a drop test by pulling off one boot at a time. If no change in rpm, that cylinder is not contributing. When doing the drop test underway, a timing gun is useful -- missing will show up as no flashing. Test an perhaps replace the 140 degree thermostat.


    • #3
      Test run with another fuel tank.


      • #4
        Thanks guys, I will try a drop test. I'll try find another fuel tank somehweres and give that a shot also. What would be the best way to replace the thermostat? They look fairly cheap and look easy to swap, but is it easy to test also?


        • #5
          T.stat on yours is up at the top of the powerhead, and easy to replace (not so easy with some of the earlier models). I test them by dipping them in a heated cup of water to see if they open. Can get fussy, and heat the water in a microwave, using a meat thermometer to measure water temp. Should open at about 140F (close when you pull it out of the water. Use a pair of kitchen tongs.) You may find that a PO removed the thermostat -- not a great idea, as the motor has to be up to temp to run well.

          Based on water temps referenced, sounds like you might do some fall and winter steelheading.


          • #6
            Thanks oldboat1 for the instructional... and yes I do some steelheading! I have not pulled the thermostat and will do so. When I test this out, do I need a new gasket? or can I reuse the one that is on there?

            I was messing around with the engine and did a drop test on each cylinder. The motor died pretty much immediately after pulling each plug which shows that they're each contributing. I also briefly messed around with a ignition gap tester and tried to get it to jump a gap. I wasn't able to, but the motor started on the 2nd pull, so I suspect that I wasn't grounded properly or something and will give that another try.

            What I did find which was very interesting was that I was just checking out the wires and happened to lift one of them up... and it snapped off right at the ring connector as it was connected to the engine block. I wasn't sure what it was, and decided to try start the engine up again... and it fired right up. What I wasn't able to do was kill the engine, and sure enough as I traced it back, I found that the wire was going to the kill switch. I ran to the auto store and got another connector and reconnected, and now the engine starts and properly kills without issue. What this means though is that the kill wire was connected to the block VERY loosely... enough to break that it came off when I lifted it with one finger. I'm not sure if it's possible that that was the issue that's been plaguing me... since it really doesn't explain why the motor dies under load, but its good to get that fixed anyways.


            • #7
              Progress, sounds like. One of the kill switch grounds goes to a coil mounting bolt, and the other to the power pack by way of a single amphenol connector. You probably do have a grounding issue in using the spark tester, as you suggest. That ignition puts out a powerful spark (7/16 or so, and sharp). Both working, sounds like, but agree it's worth testing the spark again. The ground clip on those adjustable testers isn't the best -- I extend them.

              might be able to reuse the t.stat gasket, but probably a good idea just to get a fresh one on hand.

              Hey -- think Michigan trout season opens pretty quick -- this week, maybe? Steelhead can kind of spoil you, though. We fished summer runs on wet flies out in Washington state -- think it would be pretty exciting to hook up on a dry fly.


              • #8
                So I believe the first issue that I had is fixed. One recommendation of a relative, he thought it might be a venting issue with the gas can where air was somehow getting sucked in with the fuel and recommended cracking the cap when running. Lo and behold this fixed it. It now runs cleanly at full throttle for a couple of trips, but only if I leave the cap cracked. So a new tank will have to happen at some point.

                Today I had another issue though. I put the boat in, it started great on the first three pulls and runs great. However when idling with the throttle at the lowest point, it would die. It would idle fine if the throttle was a smidge above idle. It ran fine at WOT. After done with fishing and heading back to launch, I couldn't get the motor to stay started. The motor catches and runs for a few seconds then dies. Choking it helps temporarily then kills it. Keeping the throttle slightly open as well as the choke was the only way I was able to get it catch and run for a few min. I was able to get it running at WOT by pulling choke to half open and keeping RPMs a little higher then shifting into gear and increasing RPMs. I closed the choke at this point and it ran great at any speeds above 5 mph.

                I did a lync and sync, and verified that the throttle butterfly is completely closed and starts to open at the mark on the cam so I don't want to raise the idle speed. Does this sound as simple as my lean/rich mix being a ways off? It should be simple, but I was confident I had that dialed in as well, and now not so sure.


                • #9
                  I have a couple of mid-80s 9.9s, and find that the idle mix needs to be set a little richer for cold starting -- return to leaner setting after warmup. About 1/4 turn richer.


                  • #10
                    Insinkerator Pro 750 -- very quiet/powerful. New kitchen installation approx. 6 mos. ago. No issues.

                    (But not an Evinrude or Johnson, as far as I know....)


                    • #11
                      Sign up today
                      Originally posted by oldboat1 View Post
                      Insinkerator Pro 750 -- very quiet/powerful. New kitchen installation approx. 6 mos. ago. No issues.

                      (But not an Evinrude or Johnson, as far as I know....)
                      Spammer gone. Thread closed.
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