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Evinrude power loss troubleshooting

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  • Evinrude power loss troubleshooting

    I'm having a problem with my 1990 Evinrude 70hp losing power while on plane. The problem has been intermittant and it doesn't show the same exact symptoms every time out. I have a really good mechanic who does my work for me, but when the problem first surfaced I immediately checked all the obvious stuff related to gas. New, gas, new tank, new hoses, etc. Same problem, runs good at idle AT FIRST then put it up on plane, run for a bit then it looses power and sometimes cuts off, but most of the time just bogs down until I am at 3/4 throttle and barely making way.

    So after checking the gas I took it to my mechanic who suggested an ignition problem. First they checked compression which was on the money between all 3 cylinders....and had good spark on all 3 cylinders. They put it in the test tank and couldn't get it to fail. Being an intermittant problem my mechanic suggested that it could be the power pack. I agreed and got it replaced. They tested it again after replacing the pak - all looked good. I took the motor out.....same problem reared it's ugly head. Took it back, ran it in the test tank and I was there. It ran like a scolded dog for 20 minutes - no problem. Well, he said he would still dig deeper...took the flywheel off and the stator showed signs of melting. Went ahead and replaced that...while he was in he also replaced the recitifier. Felt certain this had to be the problem and that the motor was failing after heating up. Tested the boat in the tank after replacing the stator and all was good. I get the boat and take it out.....same old problem. At first it seemed like it might do OK.....ran OK at idle speed and too off like a shot from a gun when putting up on plane - for a second I thought all was good....then it bogged down again....AHHHH!!!

    Going back to the basics I got a spare gas tank that my buddy had been running on his Evinrude all week and tried that just to rule out gas again. Same old problem........sounds like it's running on 2 cylinders or not getting gas. No problem starting and it normally runs at idle speed well and just gets worse when runnning it hard.

    My mechanic says they could trouble shoot it fairly easily if they could just get it to fail in the tank. Frustrating that it runs fine in the tank, but awful when out on the water.

    Hopefully he ran it in the tank again this evening and got it to fail. If not I suggested going ahead and replacing the 3 coils. He also said he was going to pull the carbs and take a look for any varnish, etc.

    So does anybody have any bright ideas. This is the most frustrating thing I have gone through with an outboard and I have had a bunch. Maybe a reed valve?? I don't think that would be intermittant though.

    Any thoughts or help would be appreciated!


  • #2
    Re: Evinrude power loss troubleshooting

    Take your mechanic out for a ride.
    If I wanted your advice my wife would have told me to ask you for it.

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    • #3
      Re: Evinrude power loss troubleshooting

      Already asked, unfortunately I don't think he really has the time. He's a really good mechanic thought and has always treated me well in the past....that's why I hesitate to take it somewhere else...especially since he knows the history.:$

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      • #4
        Re: Evinrude power loss troubleshooting

        I'll bet a fuel restriction.Once the carb bowls ,or A carb bowl goes empty,you may be losing a cyl.How about a pinched fuel line,or a fuel line that has swollen inward,cutting fuel.I doubt that tank testing is giving the eng. the run for the money it needs to fai;l

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        • #5
          Re: Evinrude power loss troubleshooting

          When you tried your buddies tank,did you use his fuel line as well?? Just a thought!

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          • #6
            Re: Evinrude power loss troubleshooting

            Sounds like ignition to me. How old are your plug wires and other ignition components?

            Also, have you tried running it with the cowling off? Sometimes exhaust leaking into the cowling can cause problems as can cowling fasteners being too close to plug wires (or so I've read in other places here for the latter).

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            • #7
              Re: Evinrude power loss troubleshooting

              Also, how long do you have to run the motor before the trouble starts?

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              • #8
                Re: Evinrude power loss troubleshooting

                I like mikesea's suggestions. At worst pull your carbs and rebuild them. The carb kit price is very reasonable and it is something you can do yourself.
                If I wanted your advice my wife would have told me to ask you for it.

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                • #9
                  Re: Evinrude power loss troubleshooting

                  Well, when I ran my buddies gas tank I used his hose. I have a water sepeartor and by passed all of that with his tank and a hose directly from the tank to the motor. By doing this I pretty much ruled out the fule line, gas, tank etc.

                  Most of the ignition components have been replaced at one time or another but I'm not exactly sure when. I think I am going to rebuild the carbs just as a precauson. We'll see.......but boy it is frustrating!

                  Petty - funny you asked about running it with the cowling off. I did do that on the water because other than load issues, that's the only thing I can see different from them running it in the tank and me running it on open water. Unfortunately running it on open water produced the same result. I run it for a few minutes at idle speed out of no-wake and it seems to run OK, then I put it up on plane and it takes off and bogs down little by little....getting worse by the minute. Normally by the time I am back to the no-wake zone I have it pegged at 3/4 throttle and I am barely making way.


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                  • #10
                    Re: Evinrude power loss troubleshooting

                    Oh, so it's a gradual degradation in performance not quantum leaps like you'd get with a cylinder cutting in and out.

                    Interesting.

                    Maybe it's overheating. Although, that's still kind of odd behavior even for that. But for the sake of argument, how's your water pump and thermostat?

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                    • #11
                      Re: Evinrude power loss troubleshooting

                      Take a timing light and a buddy out next time. When it starts to bog have him check for loss of spark. I would still do the carbs if they haven't been done for a while. Put your fingers on the head and see if you can hold them there for a good five count. iwombat could be right but it is odd.
                      If I wanted your advice my wife would have told me to ask you for it.

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                      • #12
                        Re: Evinrude power loss troubleshooting

                        How about the obvious-coils. do they have a good ground? are they getting hot and failing? just my .02

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                        • #13
                          Re: Evinrude power loss troubleshooting

                          After I run it awhile I can hold my fingers on the cylinder head so I don't think it is overheating. The warning horn works fine so I know it is not going into SLOW.

                          Water pump seems to be fine - not sure about the thermostat.

                          I thought to replace the coils just to see what happens since it is an easy and cheap fix. I tend to think that it is failing when it gets hot, but I would think that it would get hot running in the tank also and then it would start breaking down.

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                          • #14
                            Re: Evinrude power loss troubleshooting

                            Instead of replacing the coils pull them off and clean the grounding straps and the block where the straps make contact and give her another try.

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                            • #15
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                              Re: Evinrude power loss troubleshooting

                              As the engine starts to die,did you try squeezing the ball to force gas up to the engine.If not,try it.If it begins to run,its the fuel pump,assuming all the lines are air tight.What kind of fuel pump do you have. ?Are you using the old style that has 2 screws and a removable slotted screw so you can access the screen.Is the screen clean. Or is it a VRO seperate oil and gas.?

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