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  1. #1
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    Jul 2009
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    Default 1985 Johnson 70 HP

    I have been trying to cure my acceleration problem for 2 years and nothing I have done has had any effect.*It doesn't get any worse but it doesn't get any better either.*The problem is when I move the handle forward to accelerate from idle it wants to bog or stall unless I hit the choke and give it a shot of gas.* Then it takes off and runs fine.* Sometime it will take off and run OK the first time when I leave the launch ramp but after that initial takeoff it will revert back to its old ways on subsequent takeoffs. Then if I don't hit the choke on acceleration it will just die.* The motor is on a 1985 Grumman 5.0 which is a fairly heavy aluminum boat for its size. Once I get past the bogging and it takes off I have no problem getting up to 5000 RPM and 25-29mph*depending on how many lard bellies I have on board.
    *My compression is between 120 and 130 on all 3 cylinders.*
    *I have totally disassembled, cleaned and rebuilt the carbs twice, including pulling all the soft plugs, soaking in solvent, shoving wires thru all the orifices, examining under magnification etc.
    *I removed the high speed jets (both times)*and made sure they were clean and even tried putting in slightly oversize ones.
    *I have checked the synchonization of all 3 carbs. *
    I bought a spark tester and I have a 7/16 bright blue spark on all 3 cylinders (I replaced all 3 coils anyway out of frustration since nothing else worked).
    *I have replaced the VRO pump and all the hoses attached to it.*
    *I have checked the timing at idle and fully advanced (using a method found on this forum).* When I checked the timing I made sure the pointer was set right on TDC using a depth mike to make sure the piston was all the way up. *
    I am at wits end and ready sink this boat to create an artificial reef.* Judging from posts I have been reading on this forum for the past 2 years this seems to be a common problem with this motor. Is there anything else I should try?

  2. #2
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    Sep 2010
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    ontario
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    Default Re: 1985 Johnson 70 HP

    What if anything has been done with the idle orifice plug.--------------75 HP model had adjustable needle for idle , thought of converting to that ??

  3. #3
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    Default Re: 1985 Johnson 70 HP

    So far I have only removed and cleaned the idle orifice plug and the passageways behind it. What is involved in converting to the adjustable needle? Is it complicated to adjust the idle on a 3 carb setup? It's pretty easy on single carb small outboards, chainsaws etc but I haven't done 3 carbs.

  4. #4
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    Default Re: 1985 Johnson 70 HP

    Why would it be difficult ?????

  5. #5
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    Default Re: 1985 Johnson 70 HP

    So do I just remove the orifice plug and install 0315232 retainer and 0330129 needle valve?

  6. #6
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    Default Re: 1985 Johnson 70 HP

    The other thing you could try is to open the idle orifice up say 0.002" at a time and see what that does.

  7. #7
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    Default Re: 1985 Johnson 70 HP

    I'll give that a try. I have access to pin gages and all sizes of drills and reamers. Thanks.

  8. #8
    Join Date
    Jun 2011
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    SA Tx
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    242

    Default Re: 1985 Johnson 70 HP

    I have a 1985 johnson 185,and it was doing the exact same thing you are describing.I finally adjusted my floats just a tad higher than the specs say and all my problems went away.What have you got to loose!!!

  9. #9
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    Sep 2010
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    ontario
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    Default Re: 1985 Johnson 70 HP

    Cisco,--------Have you found the reed valves on your 185 HP motor ????????????????

  10. #10
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    Jun 2011
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    Default Re: 1985 Johnson 70 HP

    Whats up racerone,I havnt messed with it been working alot of hours.

  11. #11
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    Default Re: 1985 Johnson 70 HP

    I just opened up the .028 idle orifice to .031. Our drills only went down to .040 but we had some nice carbide 1/32 end mills which I just used to ream the holes up by hand. I'll put them back in tonight and try to get the boat in the water sometime this week. I also notice that this 70 HP motor can have a .052 high speed orifice or a .057. My carbs came with .052 but this motor has a rebuilt powerhead which is not the original powerhead. When I bought this powerhead I had to put my carbs and intake, electrical system etc on it. I wonder if this power head needs the bigger jets. I had an extra set of .052 jets so I just drilled them .005 bigger and i'm thinking of putting those in too.

  12. #12
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    Default Re: 1985 Johnson 70 HP

    I took the boat out last night and it still bogged and had to be choked on acceleration. Also my top end was about 300 rpm less with the drilled out high speed jets. I am going to put the 54 jets back in. I don't know if I should try and drill the idle jets another .002 bigger or try tweaking the floats next. Ciscokid when you say adjust the floats higher do you mean so that it allows more gas into the float bowl before the float shuts it off?

  13. #13
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    Default Re: 1985 Johnson 70 HP

    Quote Originally Posted by fmarando View Post
    I took the boat out last night and it still bogged and had to be choked on acceleration. Also my top end was about 300 rpm less with the drilled out high speed jets. I am going to put the 54 jets back in. I don't know if I should try and drill the idle jets another .002 bigger or try tweaking the floats next. Ciscokid when you say adjust the floats higher do you mean so that it allows more gas into the float bowl before the float shuts it off?
    Sorry for the wait i work weird hours!!Ok when you are installing your float the carb is upside down,bend the float to were the bottom of float is even with the carb body where the gasket go.it will just be the very end of the float that is even with carb body not the entire bottom of float.try that and see what happens,if that dont work then adjustit different ways,thats what i did and i finally got it rite.Let me know if you got this message.My real name is mike.

  14. #14
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    Default Re: 1985 Johnson 70 HP

    You might be getting to much gas or not enough,like i said in the quote,you have to play with it untill you get it rite.I did all the stuff you are doing also,So dont feel bad!!

  15. #15
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    Default Re: 1985 Johnson 70 HP

    I suspect it's not getting enough gas since it needs the extra shot of gas from the choke solenoid in order to take off. I'll try adjusting the floats 1/8" toward the carb body and see if it makes any difference.

  16. #16
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    Default Re: 1985 Johnson 70 HP

    What do I need to do to change from the fixed orifice to the needle valve for the low speed jets? From the diagram it looks like those carbs can have either a fixed .028 orifice or the needle and retainer. I have a bunch of the retainers that came with rebuild kits. Do I just need to buy 3 needle valves P/N 0330129 and remove the orifices and then install the needles and retainers? The procedure to set the needles doesn't seem to complicated and I think it would save a lot of trial and error in drilling out orifices.

  17. #17
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    Default Re: 1985 Johnson 70 HP

    Well, since I could not get a direct answer as to whether I could swap the fixed orifices for needle valves I decided to order some needles and see if they fit. They don't. Another $40.00 into this bottomless pit. So it looks like if I want to switch to adjustable needle valves I would have to buy 75 HP carbuerators. I guess I'm back to reaming the orifices up .002 at a time. I'll try playing with the floats too. I just have no idea if I'm heading in the right direction.

  18. #18
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    Default Re: 1985 Johnson 70 HP

    Sorry i have been working alot of hours latly.I have never went from fixed to adjustable.Try playing withyour float adjustment just a we bit at a time.I you were close to where i live i would come help you!!! I know how you feel.

  19. #19
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    May 2008
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    Default Re: 1985 Johnson 70 HP

    Sounds like you have one of these engines that just dont want to play ball...
    If you lost rpm with a bigger main jet, then your original main jets should of been fine.
    What I would be doing, would be, set your floats as per the manual, make sure your nozzle gaskets are in place and in good order.
    Then I would be increasing idle jet size by .002" until you either a) get the engine running right, or b) your idle becomes too rough...
    If your idle becomes too rough before that engine runs right, I would then start to look at other things other than your carbs...

  20. #20
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    Default Re: 1985 Johnson 70 HP

    I put the .054 main jets back in. I checked the floats and bent them up about 1/16" from the nominal setting. I re-checked the timing and it is fine. I also just put new connectors at both ends of my fuel line since they are cheap and are easy to replace. It idles fine at about 1100 rpm on muffs in the driveway. I will try it on the water the first chance I get and see if there is any improvement. All this thing seems to need is a little more gas when I initially try to accelerate, otherwise it runs fine. If I don't see any improvement the next time I have it on the water, my next step will be to buy a set of 75 hp carbs with adjustable needles. I can't find anything else wrong with this motor. The compression is fine, spark is good, all fuel lines, hoses and pump have been replaced. At least with the adjustable needles I can make adjustments while I am on the water and hopefully get this dialed in.

  21. #21
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    Aug 2008
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    Mims, FL, USA
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    Default Re: 1985 Johnson 70 HP

    Just wondering why you have not mentioned the timing pickup point as the throttle advances? If it were me, I would adjust it to give more advance before the throttle begins to open and see what happens. This is a free "test" or adjustment, and is certainly much easier than drilling jets.
    Post back please. I am interested in the fix.

  22. #22
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    Default Re: 1985 Johnson 70 HP

    I have tried adjusting the timing pickup point by two turns in both directions and it had no affect on the problem at all.

  23. #23
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    Default Re: 1985 Johnson 70 HP

    Two turns???? It should be a roller that you move toward or away from the throttle cam via a single screw that clamps the roller in place. If I am wrong, sorry, but that is the normal method for coupling the throttle to the ignition linkage.
    I don't know your exact engine setup.

  24. #24
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    Default Re: 1985 Johnson 70 HP

    I thought you meant the linkage that goes to the throttle cam back toward the arm that connects to the timer base. It has a nylon triangular shaped thing threaded on the end of a rod. If you take off the clip you can screw the nylon triangle back and forth. I think I know what you mean now. You are talking about that little arm with the roller on the middle carb linkage. Right now I have it set so the line on the cam is pointing right at the center of the roller when the cam first engages the roller as per the picture in the shop manual. So let me know if I have the concept right. You want me to loosen the screw on the roller and move the roller away from the cam slightly so that the timing advances a little more before the throttle starts opening. Is that correct?

  25. #25
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    Default Re: 1985 Johnson 70 HP

    Sorry...Space Shuttle launch to attend!!! GREAT!!!!

    But back to your engine...

    Yes exactly. In other words, when you begin to apply throttle, set the roller so that the linkage advances the timer base BEFORE the carb throttle plates begin to move.
    Your description of how the marks line up is correct, but I kinda want to see if your motor needs a bit more timing advance as it is throttled up.

  26. #26
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    Default Re: 1985 Johnson 70 HP

    I will have an opportunity to take the boat out Tuesday or Wednesday. I will give your suggestion a try and let you know the results.

  27. #27

    Default Re: 1985 Johnson 70 HP

    Hello I have read your post's I have A 1988 70hp VRO evinrude that has never been touched and now has the same problem.
    The main thing that started its demise is sitting. I did the usual made sure all ports and jet's were 100% clean.
    Made sure linkage connections were good. For me I thought it was A slam dunk to fix oopps.
    I have read up on some additional things to check it mentions a check valve in the cylinder drain.
    they go onto say the engine will idle poorly and not achieve max RPM. I'm pushing a 28' pontoon and I've seen 6000 + and now struggle to get 5000. And oh my the stalling I believe I have found the port they mention. my problem is I cant be certain its A 5/32" barb just below the lower carb's right mounting bolt. This is A hose that connects to the bottom of the air box. And would make sense that A check valve is used to vent unused fuel and oil after shut down. At the same time not allowing a vacuum leak. Has anyone seen or heard of this drain/check valve ?? If so whats involved in changing it??
    And is this were it is ??? the book was no help here

  28. #28
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    Default Re: 1985 Johnson 70 HP

    I know the hose you are talking about. It connects to the air box at the bottom. I have no idea what the hose is for since it is not mentioned in my book either. I don't ever recall getting my motor above 5000 rpm. My problem is only when I first try to accelerate. Once I hit the choke a little it will take off and run fine. If anybody knows what this hose is for and how to check it out to make sure it is working right I would greatly appreciate some insight. It will give me one more thing to try.

  29. #29
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    Jan 2010
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    Dayton, OH, USA
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    Default Re: 1985 Johnson 70 HP

    I had similar problems with an '83 70hp evinrude. Turned out to be the fuel line from the tank. The squeeze ball had a crack in it. Also replaced all fuel lines with the new "ethanol resistant" hose as it was all cracking and disintegrating from the new ethanol gas.

  30. #30
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    Default Re: 1985 Johnson 70 HP

    Where the hose attaches at the intake manifold / block is listed as a nipple and not a " check valve "------------It simply sucks in any spillage from a flooding carburetor and is a " safety item " nothing else.

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