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Mercury 80 hp timing

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  • Mercury 80 hp timing

    OK, I have read a bunch of posts on tuning the timing of an outboard. However the question I have is if the timing of off, or needs to be adjusted slightly, how to do you make minor adjustments? Is there a screw or a bolt somewhere that makes these minor adjustments, or what? When I look around my engine, I do not see any obvious signs of something to adjust the timing a degree or 2 if needed.

    I have a Mercury 80hp blue stripe with the thunderbolt ignition. 1983 I think.

  • #2
    Re: Mercury 80 hp timing

    Get a manual then follow the procedure for doing a link & sync. Be sure to do it in the steps given. There is no magic screw.
    "A manual is a cheap investment"
    Fair Winds and Following Seas
    PTC USN ret


    • #3
      Re: Mercury 80 hp timing

      As bhile said you will need a manual to do this in the correct order and you will need a timming light. There are several adjustment points in the link and sync.


      • #4
        Re: Mercury 80 hp timing

        Every time I go to a marine shop I cannot find a manual for my type of motor. It would appear that the engine is a 1983 blueband 80hp with thunderbolt ingnition. I have seen the manuals in an isle, but never for motors my age.

        Come to think of it, I am not 100% sure the year of my motor.
        Serial number is S/N 7153084 if anyone can help me find the year.


        • #5
          Re: Mercury 80 hp timing

          That shows up to be a made in Canada Motor 1981/1982.


          Manual specs are different for each but this is close enough to get them all REAL close. This assumes nothing is broken or "wrong" with it. This also assumes that the timing pointer is properly adjusted (if adjustable) to accurately read TDC of the #1 piston.

          This basic procedure will work for all the 2/3/4/6 cylinder inlines from 1960 to 1988. It's not for the newer 3 and 4 cylinder loopers.

          Engine off

          Disconnect throttle cable

          Pull throttle arm to full throttle and verify carbs open fully. Adjust main throttle stop so that the carbs are JUST hitting thier own little throttle stops. The idea here is that you want the screw stop and NOT the carbs acting as the "final stop" for your throttle lever.

          Return the throttle to idle, carbs should be closed. Set all idle screws to 1 3/4 turns out from lightly seated.

          Remove all plugs except #1, hook a timing light to #1. Then follow the narritive.

          When the throttle is in the idle position the carbs should be fully closed and the ignition retarded. It is the amount of retardation that determines your idle speed and is set later with the idle stop screw.

          Timing Event One - throttle pickup.
          As the throttle is advanced, the spark timing advances toward TDC and then to before TDC. As the timing is just passing TDC the 1st (minor)throttle pickup should hit and start to open the carbs. Use the timing light. Adjust the tang or trigger screw to make this a reality. All of them are speced different, but if the 1st pickup hits at 3-4 degrees BTDC advance - you win. Use the timing light with a friend cranking it to complete this setting.

          Timing Event Two - max advance.
          As you continue to advance the throttle the timing will advance while the carbs slowly open a bit more. The next adjustment is max advance, this is the point where the distibutor (or trigger) can advance no more. Set the max-advance stop to 21 degrees for "direct charge" crossflow inlines and 34 degrees for the older plain vanilla crossflows. Use the light, - err to the side of caution.

          Right after max advance, further throttle motion should cause the second throttle pickup to hit and open the carbs to full. You already set that -now verify it.

          Leave the throttle cable disconnected and go to the water. Leave the boat strapped to the trailer and back it in so it's deep enought to run. Have a friend crank it while you operate the choke and throttle. Warm it up at 1500 rpms's.

          When "warm" adjust the idle stop screw for about 800 rpm and then ajust your idle needle(s) in (one at a time) till the motor stumbles. Quickly backing it out 1/2 turn from "stumble" will usually save it from needing a re-start. Do that for all the idle screws. Re-set idle stop for 800.

          Now have your friend put it in gear (make SURE you are on the transom NOT in the water) and reset your idle stop for as low as you can get it. 500-600rpm is great if your old reeds will let it idle that low in gear. Now, re-adjust the idle screws, in to stumble, then 1/2 turn out. When you've gone back and forth with that a few times and have it "perfect" - adjust each one out 1/4 turn.

          Reset the idle stop so that it's about 700-800 out of gear and 500-600 in gear. Sometimes bad reeds won't let you get that low, you've GOT to get it under 1000 in neutral (worst case) to avoid beating up your lower unit when you shift into gear, even 1000 is "bad" but like I said "worst case".

          Now adjust (and hook up)the throttle cable so that with the shifter in neutral, there is light to moderate pressure holding the throttle arm against the idle stop.

          Take the boat off the trailer and go out in the water. Try the hole shot. If it falls on it's face try adjusting the idle screws out 1/4 turn at a time (all of them together) till you can get a hole shot. You can kind of do this on the trailer at the ramp, but it's not really safe for you, the boat, or the tow vehicle.

          You're done.

          Thanks to Mr. Canino for this write up.


          • #6
            Re: Mercury 80 hp timing

            There is just too much to take in on this type of repair. There are too many adjustments, and things that need to be done in and out of the water. I think I will just take it to a boat shop and have it timed/tuned.


            • #7
              Re: Mercury 80 hp timing

              OK, so let me ask this.

              I removed the #1 spark plug, and used a screw driver as I turned the flywheel by hand. when the cylinder is at the highest point, the lines and numbering on the flywheel are not even close to the pointer, I mean they are like on the other side of the motor than the pointer. Does this mean the flywheel was just put on wrong, or it is way out of timing? It is a 2 stroke engine.


              • #8
                Re: Mercury 80 hp timing

                It sounds like you're a victim of a "take the flywheel apart and forget about putting it together correctly" bozo, happened to me. Take the flywheel apart at the hub and set it to the timing marks.


                • #9
                  Re: Mercury 80 hp timing

                  Ok so I move the #1 cylinder to the highest point, remove the flywheel and place it to the 0 mark?


                  • #10
                    Re: Mercury 80 hp timing

                    Yep you got it.


                    • #11
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                      Re: Mercury 80 hp timing

                      So if I use a timing light and my timing is off what do I adjust to move the timing to the correct number? So if my timing is 2 degrees off what do I adjust to move it 2 degrees for correct timing?