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  1. #1

    Default 85 Evinrude 40 horse bogging and surging under load

    Hi everybody I've got a little bit of a weird one here. This engine starts idles and will putt at 3 miles per hour no problem, soon as I try to crank her up it just bogs and has a intermittent surge in revs every four to five seconds. Tank is clean new bald just replaced, carbs are spotless. I pulled the fuel lines off both carbs and turn the engine over it appears like there's plenty of gas coming out. While it's bogging pumping the bulb has no effect. Strong blue spark at both plugs. It's got the vro fuel pump that's been modified for premix. I'm scratching my head gentleman I'd love some advice. Thank you.

  2. #2
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    Default Re: 85 Evinrude 40 horse bogging and surging under load

    If it has an electronic choke, hit it when it starts to bog down and see if it speeds up. The electronic choke (EC) squirts fuel directly into the intake manifold bypassing the carb jets.

    If it has no electronic choke, I do not know, maybe squirt some gas into the carb hole and into the intake manifold to simulate the electronic choke? The amount the EC sprays is like what you'd see from a small needle. Make sure the gas you squirt has oil.

    If it worked fine before this episode you describe, then it's likely clogged high speed jets (you said you tested the spark) . You'll have to take the carbs apart and spray every orifice with CRC Isopropyl Alcohol spray using the straw. That is the way I do it because OMC tells you to use alcohol so as not to harm the carb with acetone, and the reason why I use it in spray form, is that I can actually see if it has cleared out the orifices, for you see the spray pattern come out the other end.
    Last edited by Klink; 06-24-2018 at 05:11 AM.

  3. #3

    Default Re: 85 Evinrude 40 horse bogging and surging under load

    [QUOTE=Turnanburn;612243] there is an electric choke and I have pulsed it and it takes right off. I will spray some of that alcohol product into the carbs and give it a run. Is it safe to assume the fuel pump is okay because pumping the bulb underway has no effect?

  4. #4
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    Default Re: 85 Evinrude 40 horse bogging and surging under load

    It is not just spraying alcohol into the carb, you have to take the carbs apart and clean all the jets and orifices that the fuel goes through. It's likely just the high speed jets , but it is always good to clean all the orifices since it takes an extra 30 seconds to do.

  5. #5
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    Default Re: 85 Evinrude 40 horse bogging and surging under load

    [QUOTE=Turnanburn;612285]
    Quote Originally Posted by Turnanburn View Post
    Is it safe to assume the fuel pump is okay because pumping the bulb underway has no effect?
    I would say so.

  6. #6
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    Default Re: 85 Evinrude 40 horse bogging and surging under load

    I once had a zero turn mower that was backfiring every so often. A forum told me to clean the carbs so I took them apart and cleaned them. then tried it out and it still backfired. I told the forum and the man asked me if I had sprayed every jet, I said I hadn't, then he said you have to do it. I went back and sprayed every orifice and found the clog and cleaned it. The engine never backfired again. You have to spray into the jets and orifices till the straw spray comes out the other end as well as it comes out the straw by itself

  7. #7

    Default Re: 85 Evinrude 40 horse bogging and surging under load

    Quote Originally Posted by Klink View Post
    It is not just spraying alcohol into the carb, you have to take the carbs apart and clean all the jets and orifices that the fuel goes through. It's likely just the high speed jets , but it is always good to clean all the orifices since it takes an extra 30 seconds to do.
    So I took the carbs off sprayed carb and choke cleaner Evinrude Johnson alcohol spray into every orifice and was pretty positive everything was clean put carbs back on and same problem. These carbs don't have much going on inside them, no adjustment screws. I'd love to rule out the fuel pump . I winged it over and both lines were pumping gas not just a trickle either. Something I tested but don't know much about is that while running I pulled one plug and it still sputtered, pulled the second plug and it died right away, I feel pretty confident those carbs are clean. Could be an ignition thing? Maybe something weird because both plugs have good blue Spark.

  8. #8

    Default Re: 85 Evinrude 40 horse bogging and surging under load

    I understand what you're saying it's very important to be thorough, tiny little holes are easy to clog. I sprayed the hell out of those things and the spray was coming out the other end with Force on each hole.

  9. #9
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    Default Re: 85 Evinrude 40 horse bogging and surging under load

    Quote Originally Posted by Turnanburn View Post
    So I took the carbs off sprayed carb and choke cleaner Evinrude Johnson alcohol spray into every orifice and was pretty positive everything was clean put carbs back on and same problem. These carbs don't have much going on inside them, no adjustment screws.
    You took apart the carb bowl and cleaned the bowl, float, and all in there?

    Do you have a manual?

  10. #10
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    Default Re: 85 Evinrude 40 horse bogging and surging under load

    Quote Originally Posted by Turnanburn View Post
    Something I tested but don't know much about is that while running I pulled one plug and it still sputtered, pulled the second plug and it died right away, I feel pretty confident those carbs are clean. Could be an ignition thing? Maybe something weird because both plugs have good blue Spark.
    It is a two cylinder engine, you mean that:

    You pulled one plug wire and it was able to run on one cylinder.

    Then you connected it back and it ran normal with two cylinders like it should.

    Then you pulled the other plug wire and it turned off?

  11. #11

    Default Re: 85 Evinrude 40 horse bogging and surging under load

    Quote Originally Posted by Klink View Post
    It is a two cylinder engine, you mean that:

    You pulled one plug wire and it was able to run on one cylinder.

    Then you connected it back and it ran normal with two cylinders like it should.

    Then you pulled the other plug wire and it turned off?
    yeah. It didn't run well on just the lower cylinder but it did sputter along for a few seconds. My brother's got the manual. Thanks for your time by the way.

  12. #12

    Default Re: 85 Evinrude 40 horse bogging and surging under load

    Also to answer your previous question I did dismantle the carbs fired cleaning solution into the Jets pulled the float and needle valve out everything that was visible. They honestly look brand new. I really wanted to find some junk in there.

  13. #13
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    Default Re: 85 Evinrude 40 horse bogging and surging under load

    What are your compression numbers? Try holding your hand over each one of the carbs and see if it smoothes out just cover about 3/4 of the carb. Always check compression first then spark then fuel. If compression is good then check for spark with a open air spark gap tester. That ignition should jump a 7/16 gap with a crisp blue snap. Get back with those numbers then you can focus on fuel!
    It takes a nickle to go first class!
    If it aint broke dont fix it!!

  14. #14

    Default Re: 85 Evinrude 40 horse bogging and surging under load

    Quote Originally Posted by kimcrwbr1 View Post
    What are your compression numbers? Try holding your hand over each one of the carbs and see if it smoothes out just cover about 3/4 of the carb. Always check compression first then spark then fuel. If compression is good then check for spark with a open air spark gap tester. That ignition should jump a 7/16 gap with a crisp blue snap. Get back with those numbers then you can focus on fuel!
    thanks everybody for your responses it turns out that I hadn't cleaned the carbs as well as I should have. I poked a little fine brass wire up through the center needle jet and now we are cruising and having fun thanks a lot everybody. They look so clean but whatever ,lesson learned

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