• If this is your first visit to the iboats.com Boating Forums, be sure to check out the FAQ. To post a question or comment, begin by signing up. To start viewing messages, select the forum that you want to visit from the selection below.

Announcement

Announcement Module
Collapse

Help Tip: If you have a question that has not been answered to your satisfaction in the archives, it is always best to start a new thread of your own. By starting your own thread, you will receive the maximum number of views by forum members.

Below are some additional forum policies in hopes of all iboats members will follow, Thank you.

1. Please do not reply to old threads or hijack existing threads. Old threads of a technical nature are like a library book, Please do not write in them.

2. Old threads should be considered archives and used for reference only. Please do not reply to them.

3. Do not take over someone elseís thread (aka hijack) with your own question, even if it is similar. If you have a question that has not been covered to your satisfaction in the archives, it is always best to start a new thread of your own.

4. If you have a question for the original poster (OP) and the thread is over 30 days old, send the OP a PM, he may not even visit the forums any longer, or may not notice your question in the old thread.

5. By starting your own thread, you will receive the maximum number of views by forum helpers that may not even notice your question when itís posted at the end of someone elseís thread. And those answers will be specific to your particular issue.

6. Please do not post to threads that have been inactive for more than 3 months unless you are the original poster. We have very active forums and any thread that remains inactive for that long should be considered "dead". It is especially confusing when there is an entirely new question posted to an old thread.

7. Posting at the end of any thread is considered to be hijacking the original posters thread which in turn subjects the thread to be closed if it continues to happen thus not making it fair to the original poster in the future had for some reason he/she needed to return for additional information or provide an update of the problem solved which is always welcomed within a reasonable amount of time frame.

8. Please note that you should see a red banner pop up near the bottom of each inactive thread asking you not to reply to old threads. The Red banner will read: Please note this thread has been inactive for 90 days. For the best results, please start a new thread.

Thank you all in advance for doing your part in helping iboats run a smooth ship.

Additional forum rules linked below.
http://forums.iboats.com/forum-rules-guidelines-405/
See more
See less

1985 mercury 50 hp classic fuel problem

Page Title Module
Move Remove Collapse
X
Conversation Detail Module
Collapse
  • Filter
  • Time
  • Show
Clear All
new posts


  • 1985 mercury 50 hp classic fuel problem

    My friend just bought this engine,we checked compression and all four were 120 psi,new plugs,great blue spark and gas up to the strainer or filter.
    We gave it a test run and it ran great until after three quarter throttle then it bogged down.
    Back off the throttle ,ran fine.When we got back to the dock later turned it off and went to start it again,nothing,just cranked over.Took out the plugs after trying to start with choke on and found that the plugs were dry and still getting great spark.

    Getting fuel through the fuel lines all the way to the carbs,but for some reason fuel is not making it to the plugs.


    I thought maybe at first when the motor was running but would not take full throttle the problem may be the fuel pump on side of the carb,but now we are not getting any fuel to the plugs.
    Could both fuel pumps have failed?

    squeezing the bulb while cranking does not help either.

    The serial number is A 949314

    Thanks so much in adavance for answers....
    Last edited by fisherman81654; October 20th, 2013, 07:12 PM.


  • #2
    Re: 1985 mercury 50 hp classic fuel problem

    This motor does have a fuel pump on the side of each carburetor? ( two carburetors, two fuel pumps) correct ?
    Last edited by fisherman81654; October 20th, 2013, 07:11 PM.

    Comment



    • #3
      Re: 1985 mercury 50 hp classic fuel problem

      Two stroke Motors need the carbs stripping and cleaning and carefully rebuilding with new kits on a regular basis. If this is not done then there is no lubrication to the motor and failure will result. If the carbs have not been serviced recently then they should be done. This is the most likely cause of your problem.

      Comment



      • #4
        Re: 1985 mercury 50 hp classic fuel problem

        I'd pull the carbs and service them. Check linkages after reinstalling to make sure all's in sync.

        Comment



        • #5
          Re: 1985 mercury 50 hp classic fuel problem

          I agree with both of you but he did not do that.
          He did tear it down and carbs apart and found that the float neddle valve was stuck on both carb,he cleaned it some and put it back together and it started fine and ran fine till full throttle was applied then it did the same thing ,bogged down,eased off the throttle some ,ran fine.
          He did add some sea foam hoping that would clear up any remaining obstructions.

          My question is do you know what part of the carbs is causing this to do this and could it hurt the motor as far as maybe its not getting fuel to a cylinder,I dont know if thats the case.

          Personaly,I would have went with a total rebuild of the carbs.

          Comment



          • #6
            Re: 1985 mercury 50 hp classic fuel problem

            You cannot only partially clean and rebuild. Do a proper job or burn up the motor.

            Comment



            • #7
              Re: 1985 mercury 50 hp classic fuel problem

              If the carbs are not properly cleaned AND adjusted, they'll be able to provide enough fuel to the motor, especially on high demand situations at full throttle or upper rpms. Once you ease on the throttle the carb can keep up... however, is it's been mentioned by others you're walking a fine line with half *** carbs because that's where the lubrication to your motor comes from. You keep pushing it on bad fuel flow (hence oil flow) and you'll have a powerhead to rebuild or replace.

              Get a carb kit and the service manual and follow the steps.
              Best of luck

              Comment



              • #8
                Re: 1985 mercury 50 hp classic fuel problem

                [QUOTE=alfa;4416646]If the carbs are not properly cleaned AND adjusted, they'll be able to provide enough fuel to the motor, especially on high demand situations at full throttle or upper rpms. Once you ease on the throttle the carb can keep up... however, is it's been mentioned by others you're walking a fine line with half *** carbs because that's where the lubrication to your motor comes from. You keep pushing it on bad fuel flow (hence oil flow) and you'll have a powerhead to rebuild or replace.

                Get a carb kit and the service manual and follow the steps.


                I completly agree,but its not my motor.Its my neighbors motor.
                My question is what part of the carburetor is malfunctioning that causes the motor to boog down only at full throttle.
                We have sprayed fuel in the carburetors when full throttle is applied,it makes it worse .That tells me that it must be getting enough fuel at that point.We have not touched the idle screws.

                Thanks so much for the replies..

                Comment



                • #9
                  Re: 1985 mercury 50 hp classic fuel problem

                  I have the exact same engine.

                  By chance, are you using a newer fuel tank? I had the same symptoms and it turned out to be the newer EPA 2012+ non venting fuel tank that was starving the engine.

                  Comment



                  • #10
                    Re: 1985 mercury 50 hp classic fuel problem

                    Originally posted by mixerjv View Post
                    I have the exact same engine.

                    By chance, are you using a newer fuel tank? I had the same symptoms and it turned out to be the newer EPA 2012+ non venting fuel tank that was starving the engine.
                    No,but a good point tho.I'll have to get on the back off the boat while hes giving full throttle and loosen the fuel cap.
                    Maybe it is a problem like that. When we get a chance to do that I'll post results. thanks...

                    Comment



                    • #11
                      Re: 1985 mercury 50 hp classic fuel problem

                      Originally posted by fisherman81654 View Post
                      My friend just bought this engine,we checked compression and all four were 120 psi,new plugs,great blue spark and gas up to the strainer or filter.
                      We gave it a test run and it ran great until after three quarter throttle then it bogged down.
                      Back off the throttle ,ran fine.When we got back to the dock later turned it off and went to start it again,nothing,just cranked over.Took out the plugs after trying to start with choke on and found that the plugs were dry and still getting great spark.

                      Getting fuel through the fuel lines all the way to the carbs,but for some reason fuel is not making it to the plugs.


                      I thought maybe at first when the motor was running but would not take full throttle the problem may be the fuel pump on side of the carb,but now we are not getting any fuel to the plugs.
                      Could both fuel pumps have failed?

                      squeezing the bulb while cranking does not help either.

                      The serial number is A 949314

                      Thanks so much in adavance for answers....
                      I know this sounds stupid but I have the same engine and found out that when going full throttle the parts that move inside the motor pinches off a fuel line starving the motor. I shifted the line out of the way and had no problems since.

                      Comment

                      Working...
                      X