Logo
Results 1 to 21 of 21
  1. #1

    Default 1971 Evinrude 50hp Lark - can't seem to get it right

    Hi all...

    I have a 50173S 1971 Evinrude with the Selectric remote. Great looking retro style. I have it running. Cleaned the carbs, replaced the low idle air screws new. Fires right up but shakes. I let it warm up and then start dialing in the screws. I seem to have them almost seated and it still runs rich and will foul the lower spark plug or at least it looks black and wet. I can't seem to get this correct. Not sure what else I should look for. When I cleaned the carbs I tried to also set the float from the service manuals instructions. I don't do the measurement of it as it suggests but tried to get them flat. Would I tiny bit off cause the lower carb to get too much fuel? Anyway, I'm stumped. I ha e not attempted to get it timed because it looks a little difficult to do. But if that is what it is, then I will attempt that next. Any other things I should look for?

    Thanks for any help out there...

  2. #2
    Join Date
    Dec 2015
    Location
    maplevalley WA
    Posts
    5,049

    Default Re: 1971 Evinrude 50hp Lark - can't seem to get it right

    Could be the fuel pump has a pinhole in the diaphram?

  3. #3

    Default Re: 1971 Evinrude 50hp Lark - can't seem to get it right

    Quote Originally Posted by kimcrwbr1 View Post
    Could be the fuel pump has a pinhole in the diaphram?
    Brand new OEM fuel pump.

  4. #4
    Join Date
    Dec 2015
    Location
    maplevalley WA
    Posts
    5,049

    Default Re: 1971 Evinrude 50hp Lark - can't seem to get it right

    Did you replace the float needles and seats? Never put finger pressure on the float. Turn the carb upside down andcheck the float is level and parrellel with the base. If you need to adjust it pull the float and bend the arm. Thencheck it again using only the weight of the float on the needle.

  5. #5
    Join Date
    Dec 2015
    Location
    maplevalley WA
    Posts
    5,049

    Default Re: 1971 Evinrude 50hp Lark - can't seem to get it right

    Also did you replace the fuel lines? If not do that before you go through the carbs again!

  6. #6

    Default Re: 1971 Evinrude 50hp Lark - can't seem to get it right

    Quote Originally Posted by kimcrwbr1 View Post
    Also did you replace the fuel lines? If not do that before you go through the carbs again!
    I did replace them but just went down and got some hoses from autozone that closely fit. Not the OEM sizes ID. Would the wrong diameter sizes cause this issue? If so I will order the correct sizes then. Maybe that my problem.

  7. #7
    Join Date
    Dec 2015
    Location
    maplevalley WA
    Posts
    5,049

    Default Re: 1971 Evinrude 50hp Lark - can't seem to get it right

    Your issue is in the carbs did you replace the float needles?

  8. #8

    Default Re: 1971 Evinrude 50hp Lark - can't seem to get it right

    Quote Originally Posted by kimcrwbr1 View Post
    Your issue is in the carbs did you replace the float needles?
    I did not replace the float needles... ok, got it. Will do and will let you know how it goes. Thanks so much.

  9. #9

    Default Re: 1971 Evinrude 50hp Lark - can't seem to get it right

    Quote Originally Posted by HBTim View Post
    I did not replace the float needles... ok, got it. Will do and will let you know how it goes. Thanks so much.
    Wait... I did replace those. New set.

  10. #10

    Default Re: 1971 Evinrude 50hp Lark - can't seem to get it right

    Oh crap... just looked at the float needle assembly on this site, engine is a 50173S. There is a twisted wire with this kit that looks like it would be a spring that the float would rest on. I did not have this in the set I purchased, and before looking at this kit here because you suggested the float needle, I assumed that float rested on the needle without a spring. I thought that was odd but installed it. So, here is the picture I am talking about...

    https://www.marineengine.com/parts/i...mc/0396521.jpg

    That wire included in THIS kit is what I did not have in the kit I got. I think I have my problem?

  11. #11

    Default Re: 1971 Evinrude 50hp Lark - can't seem to get it right

    I feel like an idiot... of course that is the problem!!!

    Thank you so much. I am sure this is it now. I'm so stupid.

  12. #12
    Join Date
    Dec 2015
    Location
    maplevalley WA
    Posts
    5,049

    Default Re: 1971 Evinrude 50hp Lark - can't seem to get it right

    That wire is used to pull the needle open when the float drops i doubt that is the problem. Have you done a compression test and a open air spark gap test?

  13. #13

    Default Re: 1971 Evinrude 50hp Lark - can't seem to get it right

    Quote Originally Posted by kimcrwbr1 View Post
    That wire is used to pull the needle open when the float drops i doubt that is the problem. Have you done a compression test and a open air spark gap test?
    Well crap... thought that would be the issue.

    I did a compression test and both at 150 to 151.

    Open air spark I have not and not sure how to do that. Will look it up. Also just for info... I have a new solenoid, spark plugs, wires, and coil packs that I had done when carbs were rebuilt.

  14. #14
    Join Date
    Dec 2015
    Location
    maplevalley WA
    Posts
    5,049

    Default Re: 1971 Evinrude 50hp Lark - can't seem to get it right

    All it takes is a spider leg or cat hair in the needle to cause your condition. You want the compression above 110psi and even and the spark must jump a gap of at least 3/8 inch with a crisp blue snap. I would just rebuild the carbs kit #18-7042 and lightly surface the flanges on a glass table with 220 grit pulling in one direction only. Once you mount the carbs make sure they open exactly the same time and then check adjust engine sync. For engine sync there is a line on the throttle cam the carbs should just begin to open as that line passes center of the follower roller.

  15. #15

    Default Re: 1971 Evinrude 50hp Lark - can't seem to get it right

    Very good to know. I have worked on motorcycles but this is a different beast for sure. I will do exactly as you say and report back. That is a ton. If you are ever in California in Huntington Beach, I owe you several beers.

  16. #16

    Default Re: 1971 Evinrude 50hp Lark - can't seem to get it right

    Quote Originally Posted by kimcrwbr1 View Post
    All it takes is a spider leg or cat hair in the needle to cause your condition. You want the compression above 110psi and even and the spark must jump a gap of at least 3/8 inch with a crisp blue snap. I would just rebuild the carbs kit #18-7042 and lightly surface the flanges on a glass table with 220 grit pulling in one direction only. Once you mount the carbs make sure they open exactly the same time and then check adjust engine sync. For engine sync there is a line on the throttle cam the carbs should just begin to open as that line passes center of the follower roller.
    Quick question... I got that kit you suggested and used it to do the rebuild the first time. Can I use the same float needles and resurface them with the technique you suggest or is it a better idea to start over. Also, there are two gaskets that come with this kit. one is a float bowl gasket and the other I do not know. I did not use it before because I could not identify where it would go and assumed it was a universal part for cross parting other carbs that it would go on. Is that correct or should this be on the carb somewhere?

    Again thank you.

  17. #17
    Join Date
    Dec 2015
    Location
    maplevalley WA
    Posts
    5,049

    Default Re: 1971 Evinrude 50hp Lark - can't seem to get it right

    The kit is for multiple carb styles just use the parts for your carbs. You can make a spark gap tester with a plug wire and a board cut it in half and staple a gap between the two and clamp one end to a good ground and stuff the other end in a plug boot. Be sure and check adjust the sync after you mount the carbs. Preadjust the slow needles out 1 1/2 turns from lightly seated and adjust them in gear in a barrel of water or tied to a dock. You will want to final the adjustments after you run it WOT for1/2 hour or so to blow out the cobwebs. Once done you should not have to touch then until you go through the carbs again

  18. #18

    Default Re: 1971 Evinrude 50hp Lark - can't seem to get it right

    Quote Originally Posted by kimcrwbr1 View Post
    The kit is for multiple carb styles just use the parts for your carbs. You can make a spark gap tester with a plug wire and a board cut it in half and staple a gap between the two and clamp one end to a good ground and stuff the other end in a plug boot. Be sure and check adjust the sync after you mount the carbs. Preadjust the slow needles out 1 1/2 turns from lightly seated and adjust them in gear in a barrel of water or tied to a dock. You will want to final the adjustments after you run it WOT for1/2 hour or so to blow out the cobwebs. Once done you should not have to touch then until you go through the carbs again
    Ok, got it...

    Sorry, one more question. The needle valve bushing or bearing that rests at the bottom is firm in there. I poked around with a scratch all and they won't easily come out. I have looked at videos that suggest removing them to properly clean, but before I start getting too aggressive with it, I wanted to ask first. Is there a secret to getting them out?

  19. #19
    Join Date
    Dec 2015
    Location
    maplevalley WA
    Posts
    5,049

    Default Re: 1971 Evinrude 50hp Lark - can't seem to get it right

    Are you talking about the red thing with a tab? If so it should pull right out maybe use a larger wood screw to get a goodo grip?

  20. #20

    Default Re: 1971 Evinrude 50hp Lark - can't seem to get it right

    No, not that. There is a white nylon bushing just above the point that the needle sits on at the bottom of the seat. When I originally rebuilt the carbs one came out with the screw and the other one did not. I left it and replaced the other with the one supplied in the kit. Now neither of them will come out. The can also be called a needle valve bearing.

  21. #21

    Default Re: 1971 Evinrude 50hp Lark - can't seem to get it right

    Holy crap... I may be the stupidest person anywhere.

    Well, found the perfect screw size and hand screwed it into the nylon bushing very carefully... slowly backed out the bushing. It really did not want to come out. Started on the next one and got it out. Looked down both carbs and found the lower carb had a second bushing in it. I never took it out the first time. I thought I took both out but didnt. So, the lower carb that was running very rich and fouling plugs had a needle valve sitting on two bushings. It actually crushed down the bushing I left in there. Unbelievably stupid of me. Goes to show you always check twice. So now I have two carbs ready for the new kits on there way. I will follow your instructions on the float needle and fine sand it down carefully as you instructed. I have new plugs coming and have a open gap tester coming as well. No wonder I couldn't get the idle right... geez. Anyway, I will let you know next weekend how everything goes. Thanks a ton man. I wouldn't have even stated poking around if you didn't help me out here. Thanks again.

Similar Threads

  1. thunderbolt 1971 help 50hp
    By bama221989 in forum Mercury Mariner Outboard Forum
    Replies: 8
    Last Post: 04-14-2015, 04:23 PM
  2. Replies: 2
    Last Post: 09-25-2014, 05:48 PM
  3. 1971 evinrude 50hp model 50173s idle
    By olrudedude in forum Johnson Evinrude Outboard Archive
    Replies: 3
    Last Post: 07-12-2008, 11:18 PM
  4. Back again 1971 50HP
    By surfsano in forum Johnson Evinrude Outboard Archive
    Replies: 6
    Last Post: 03-07-2007, 06:40 AM
  5. 1971 Evinrude 50hp parts
    By aaron foster in forum Johnson Evinrude Outboard Archive
    Replies: 0
    Last Post: 05-16-2006, 02:25 PM

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •