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1990 Evinrude 40HP

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  • 1990 Evinrude 40HP

    Hi guys I am having some trouble and hoping someone can help me out. I recently acquired a used 1990 40HP Evinrude VRO and mounted it to my boat. VRO has been disabled and I am running premix. Took it out for the first time and it ran OK. It would want to stall when idling and I also noticed it had some hesitation at WOT. I also noticed that when pumping the primer ball it would never really get completely hard and fuel would start running out the throat of the bottom carb into the airbox.
    I kind of figured I had an issue with the needle and seat so I purchased 2 carb kits and rebuilt both as well as replaced the fuel filter. After rebuilding the carbs and reinstalling them the motor would fire up, but didn't want to stay running unless I hit the electric choke every few seconds. I tore the carbs back off and double checked all the orifices as it sounded like I was not getting enough fuel since it would run with the extra fuel from the electric choke. Reinstalled carbs again with the same issue where it wouldnt idle well. However after the rebuild the carb is no longer leaking fuel and the bulb will get hard so I think that issue is resolved.
    I pulled the plate off the throttle cable adjustment and screwed it quite a ways out bringing the idle up and it would idle that way pretty well. I also played around with the slow speed idle adjustments on both carbs. Before rebuilding it I made sure to note the position they were in by counting how many turns until seated, which was 3 1/4 on both. Played around with those and never could really get it perfect. It did idle, but pretty high RPM and my arrows on my linkage were off after that.
    I decided to take it out anyway just to test. Again, would stall when trying to put into gear, but if you pulled the high idle lever up some it would idle fine until you had to push it down to shift into gear again. Also when going WOT it acted like I was only giving it like 1/2 throttle for some reason, couldnt even get the boat to plane. I am assuming that is because I adjusted the throttle cable so far.
    Do any of you guys have any suggestions on what I should try?
    The only things I can think of are the carbs are still not adjusted correctly. I didnt mess with anything other than the slow speed jets, which I set back to what they were and also the rod that connects the two carbs together. I am not exactly sure how those were set when I took them apart.
    The only other thing is the VRO fuel pump. I was thinking about swapping it with a normal pump.

  • #2
    The first thing to do is to establish the condition of the motor.-----Report the results of a compression test first.


    • #3
      I don't have a 40 manual handy, but the 20-30 hp doesn't list an initial opening for the air mix. The 28SPL calls for 1 3/4 turns from closed. I'll guess that 3 1/4 opening on your motor might be a little rich. Absent a listing for an initial setting, I would set it at 1 3/4 and let it warm up with that setting, provided it starts and runs. Adjust for best performance from there.


      • #4
        Thanks for the replies guys. I did a compression test before buying the motor and its 120 psi on both cylinders and I have great spark.
        First time taking it out before I touched the carbs it ran pretty good compared to where it is now.


        • #5
          I stopped by a local OMC repair shop this morning and a tech took a quick look. He fired it up and played around with the linkages and mix settings and came to the conclusion it was the low speed carb jet. He said he thought it had some junk in it and needed cleaned even though I already cleaned it twice and rebuilt it. I took the carbs off and gave them to him to run through his ultrasonic cleaner. An hour later or so I got the carbs back, reinstalled them, and still have the exact same issue. It will fire right up and run great for about 5 seconds then it just dies like you are pressing a kill switch. After it dies you can fire it up and again and it does the same thing. If you try and rev the engine it will also die after a couple seconds.
          It sounds alot to me like its starving for fuel but I cant be sure.


          • #6
            We see this so often !-----Carburetors cleaned 3X or more and motor still runs the same.----More trouble shooting needs to be done.----Did you replace the water pump impeller ?-----What is your mixing ratio ?----Do you have a water separating fuel filter ?
            Last edited by racerone; February 12th, 2019, 02:14 PM.


            • #7
              Water pump was done just before I purchased it. Actually the thing wouldn't shift into reverse so the first thing I had to do was pull the lower unit and adjust the shift rod. Got that fixed.
              Mix ratio is 50/1.
              I am just running an inline fuel filter, not water separating


              • #8
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                Sounds like prior work was questionable. Make sure it's not overheating (over 160F is overheating -- too hot to comfortably touch).

                I would take the inline filter out of the system and try it. Filter might be too restrictive. Can pump some gas from the bottom of the tank and check for contamination. Put it in a glass jar and let it settle out for water and debris. (Fuel will float on top of a layer of water.)