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1986 175 HP Evinrude fuel issues

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  • #1

    1986 175 HP Evinrude fuel issues

    i have a 1986 Evinrude 175 HP 6 cylinder motor. i am havint trouble with it cutting out while under power. Going along at 4000 RPM on full plane. starts cutting out. sometimes it recovers and sometimes it dies. restart it and it gets right back up and goes. Lately it is getting worse. I can get the motor up on plane or almost there and the motor cuts out. SO here is what i know

    1. Compression on all 4 cyclinders is about 90 PSI ( a little low i know but since they are all prety even this would only result in loss of overall HP right?
    2. I have byp***ed the VRO pump and i am mixing the gas and oil 50:1.
    3. Fresh gas.
    4. pumping the ball while it cuts out does not remedy the problem
    5. holding in the key to choke it has a mild positive effect but not enough for it to recover
    6. I ran it with the gas cap off to make sure it was not vapor locked.
    7. No leaking gas around the fuel lines that i can see
    8. Had carbs off and cleaned but did not replace gaskets. they looked pretty good.
    9. Replaced all plugs multiple times.
    10. when the motor dies i can restart it and then almost get up on plane
    again.
    11. tested spark on all cylinders with a spark plug gap tool.

    I really need some help. I have spent a lot of money already and no one can figure out what it is. any ideas or thoughts? I have missed fishing most of the summer already.
    Tags: None
  • #2
    I was having the same issue turned out that one of the floats was slightly out of adjustment in carb. We cleaned them out but missed setting the float levels. May want to check it out! Hope this helps.

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    • #3
      Fuel issue

      busytom; I just had the same problem with an 84' 235hp. It would run up to 4000 and die above that, but restart. I found two possible causes, weak fuel pumps and a poor water/fuel seperator cartridge(spin on type). I replaced the pumps, did help but not solve the issue. I had recently replaced the spin-on fuel filter with an OEM OMC part number, I figured that couldnt be a problem-wrong!!!. Since I have a belly tank, the fuel pumps are not strong enough to pull from the tank and thru the filter to supply high speed reqiurements. I reinstalled the old Sierra brand filter, and it solved the issue!. I suspect that the OMC filter/seperator has probably too fine a filter medium and restricts the flow especially since the pumps have to lift the fuel approx 32" vertically. Diaphram pumps are not typically designed to"suck" fuel out of belly tanks.
      Food for thought,,,,,,,Bernie H

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      • #4
        Hmm, I wonder if that could be part of the problem I am having. My 90HP is running great but at higher RPM's the primer bulb flattens and it can be a real bear to get prime again. I've replaced the entire fuel system. I recently replaced the tank connection (6 gallon portables) but perhaps the fuel water separator is too fine as it wasn't listed on the OEM diagram.

        What micron rating is the filter that works. I have a 10 micron Sierra currently installed

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        • #5
          Bernie thanks for the information. You mentioned "pumps". Does your motor have 2 pumps? Mine has only one diaphram pump at the motor. There are no inline seperators or additional pumps. I have replaced all the fuel lines and filters, etc. Here is an update to the other things i have found. I found a deteriorated fuel line that filled my fuel filter and inlet where the fuel line connects to the motor. Little rubber pieces clogged everything up. That was problem number 1. I replaced the fuel filter and the lines to the tank. I also have a miss on cylinder 5. So i have a couple of issues. I guess one should never ***ume you are chasing one problem. I took a portable 6 gallon tank and i am doing all of my testing on that tank to isolate the problem to everything from the fuel filter in. This has been a year and i am still chasing. but now that i know there is more than one problem i hope i can get to the bottom of it.

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          • #6
            this sounds typical fuel pump problem.
            if your using just the fuel side of the old vro pump then a new fuel side kit can bo got .
            personally I would chuck the vro pump completely and go back to two old stle pumps.

            old style and new style are designed to pump from a maxim of 24 inches below the fuel inlet of fuel pump.

            inline filter is 100% not the problem, and all the tiny micron filters are not restricting too much, that's a no no.
            you can fit 10 20 and even 5 micron filters and fuel should still get pumped up good.

            a simple check is to put a gallon of fuel in a gallion can and stick the fuel pipe directly in that.
            pump the ball run the engine with the can above the engine, if engine runs ok then pump is dead.
            or if you have a fuel pressure guage check it on that .


            phill

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            • #7
              Phil thanks for the reply. I just bought a new fuel pump and installed it. I can get the motor to idle just fine. I can use the fast idle lever to get the motor up to around 4000 RPM. I do not run it very long on that setting. Just quick rev up and then back down. It does not dog out or anything. I can only reproduce this issue on the water with the motor in gear when i try to get up on plane. The other thing i can reproduce is that the motor will idle fine on the water. When i tilt the motor all the way down the motor will cut out at idle. If it is in gear and even slow speeds, it does not cut out but will not get up off of plane. Some days are worse than others. I still think it is a fuel supply issue, i just do not know where to begin to look. I would love to find the magic answer!

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