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1985 Evinrude VRO 70 Fuel Issues

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  • 1985 Evinrude VRO 70 Fuel Issues

    So I have a 1985 Evinrude 3 Cylinder 70hp. We were out on the lake last weekend, and any time I opened up the throttle for more than a few seconds it would begin to miss, cough, and sputter. Pulling the throttle back would help, but didn't solve the problem. As the day wore on it no longer mattered what speed the motor was run at. We put it on the trailer and brought it home, and I believe I've narrowed it down to the Fuel Pump being faulty. This particular motor was one of those original VRO motors, and at some point prior to me the VRO fuel pump was removed and replaced with a generic one. The issue I have is that I don't know what part number to replace it with that will give me the fuel flow I need, and there's no part numbers on the casing, so I can safely assume it's a cheapo from Amazon or something. Insights would be great. The existing one has three connections, and is laying loose in the engine case, not mounted to anything. Thanks.

  • #2
    I'm going to assume there was a time when it was working right, that it's not just a piece of junk cobbled together. That being the case, have you had it apart to see if it's not full of crud?

    Is the vacuum/pulse line in good shape? Those are getting to the age where it may have split down by the crank case fitting.

    Is there a fuel filter in the line from the tank to the pump? If so has that been checked (can you blow through it easily)?

    Has the VRO/oil pump been removed so you have to pre mix the gas and oil?

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    • #3
      438559 I believe is the part # you need.-----Are you mixing at 50:1 on this motor ?----What happens when you operate the manual fuel pump, does motor run better ?----What other trouble shooting has been done if any ??

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      • #4
        VRO pump is long gone. Fuel filter is part of the pump pictured. I am premixing 50:1. I've only had it since April, and the mechanic replaced the lower unit, the battery, plugs, main fuel linealine from the tank, and did compression check. The boat was pretty much a mess when we got it. We've reworked almost the whole thing and the motor was fine every weekend until this last one. Pumping the bulb smooths it out, which is how I've narrowed it down to the pump. Eventually it will idle down and die given enough time.

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        • #5
          Not going to say I think your diagnosis is wrong, but I will share that I believe you need a MUCH higher quality filter that what that screen in that pump is capable of.

          Here's a couple of links to pages you might find interesting-
          https://maxrules.com/fixomc-standard-pumps.php
          and
          https://maxrules.com/VRO_03-70.php

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          • #6
            So your compression check showed 140 PSI in each cylinder , yes or no ?----Have you replaced the water pump impeller ?------Made sure that high speed jets ( 5/8" long ) that are screwed into carburetor bowls are clean ?

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            • #7
              I have it written down, but the compression was fine. The mechanic took the carbs apart and cleaned them. Replaced the water pump impeller and the whole lower unit. It had a new starter, and solenoid when we bought it. Probably will put an inline filter in.

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              • #8
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                Post how your motor is running after a lake test session.

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