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Timing Light Question for Mercury 2 Stroke

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  • Timing Light Question for Mercury 2 Stroke

    Hi everyone,

    I have been getting advice from other sites and family on why I do not get anymore than 4200 rpms on my 1972 Mercury Thunderbolt 800 80 hp 4 cylinder motor. Question now is on the timing. Anyone know what timing gun I can purchase for a 2 stroke, I have seen prices from $20 to $200. Would a standard light about $30 work? Do I need a digital gun?

    Thanks!

    Mark
    Mark Kriz[br]Mako15 1974[br]Mercury Thunderbolt 800 1972[br]Maple Valley, WA[br][br]

  • #2
    Yes, a standard old style timing light will work, I use an economy model from Advanced Auto Supply.

    Is this low RPM a new issue?

    If old issue, are you over-propped?

    Are you getting full travel on the throttle control?

    Are you certain that you're only getting to 4200...is the tach selector set correctly?

    The biggie: is your link-and-sync adjusted correctly? -that is the most common issue I see wrong after someone works on carbs.
    1992 211 w/175 OptiMax
    Glen Campbell, Pa.

    Comment


    • #3
      I'm curious, what plugs are you running in it?

      NGK BUHW?
      1992 211 w/175 OptiMax
      Glen Campbell, Pa.

      Comment


      • #4
        Hi Everyone,

        The engine never ran over 4200, since I bought the boat last spring. I installed a tach, though I don't remember the pulses I set it for, but the GPS speedometer shows about 30 mph at 4200. 3000rpm shows about 23 mph, so it seems right. The prop is new, its a 13x19, same size as was on the motor when I purchased it. I rarely go over 25 mph anyway, so I didn't think it was a concern. I have read a number of posts on other sites that there may be too much strain on the pistons and could cause damage, so I am trying to find out why the lower rpms. I will purchase a 13.25x17 prop, see if it helps. A couple of people from iboats are adament about timing, so I thought I would check. Need to purchase a timing light though. I can get one for about $25.

        I have done everything to the engine except for a timing check, so I don't mind checking.

        Another post stated that I need to get a power trim, which I don't understand since there is no power trim initially, and I would assume the it wasn't on issue back in the day. Hard to find one for a 1972 thunderbolt 800.

        Spark plugs are the NGK BUHW, new too.

        Good question on the link and sync. I didn't know what that was, but I have been reading up on it in my SELOC manual. I thought I would check that along with the timing.

        Thanks for the help!
        Mark Kriz[br]Mako15 1974[br]Mercury Thunderbolt 800 1972[br]Maple Valley, WA[br][br]

        Comment


        • #5
          80 horsepower of old school Mercury should make that 15 foot boat fly. I would expect to see 40mph with light load. I expect also that 19 pitch should be about right....

          1 check you timing as you stated

          2 with engine off, advance the throttle all the way and inspect the linkage to make sure it travels enough to open the butterflies all the way.

          3 make sure all 4 cylinders are firing. with insulated pliers you can remove and replace the plug boot one at a time to listen for change in engine running. That engine will run pretty good on 3 cylinders....LOL...

          enjoy...
          [br]1994 Mako 215 Dual console Optimax 225[br]1978 Mako 19 with 90hp johnson[br]1996 Mako 22[br]1982 Mako 171 Angler 135 Black Max Mercury[br]1987 21b 225 Yamaha[br]1974 23 inboard Gusto gone.[br]1979m21 225johnson \"blue dolphin\" bought off this board and restored [br]with everyone\'s help!!Gone but not Forgotten....[br]1979 20 Mako 115 Suzuki gone[br]1977 19 Mako 115 Johnson gone[br]1976 23 Mako twin 140 Johnsons gone[br]1983 224 with closed transom and bracket[br]And 162 SOB (some other boats)[br]Venice Florida, Traverse city Mi.

          Comment


          • #6
            Hi everyone,

            Thanks for the advice. I have a question on linked and synced. I noticed when I was first rebuilding the engine that there are 2 screws locked by a bolt on a plate in front of the distributor. I thought the idle adjusting screw was literally to adjust the idle of the engine. Now I know that is wrong. So I was thinking about it last night. That screw is to adjust the sync of the distributor (spark) to the BTDC of the piston. I mention it because the idle screw was at least 1/4 inch off the distributor at idle on the throttle. It wasn't doing anything. So my engine is not synced at least for idle, which would make the engine harder to start (and it is). The mechanic at a marina set it this way for the original owner (I found much of the work done questionable). If I purchase a timing light, I can readjust any setting that is incorrect, the idle and the WOT setting. Makes me concerned about the WOT setting as well. I have been reading my SELOC manual on the process, doesn't seem too difficult.

            Does this makes sense?
            Mark Kriz[br]Mako15 1974[br]Mercury Thunderbolt 800 1972[br]Maple Valley, WA[br][br]

            Comment


            • #7
              It has been a LOOOOONG time since I worked on a distributor outboard so I am really of little help. Hopefully your timing light will indicate your idle timing and your above 2500rpm timing...set it to your specs in the manual and give it a whirl....
              [br]1994 Mako 215 Dual console Optimax 225[br]1978 Mako 19 with 90hp johnson[br]1996 Mako 22[br]1982 Mako 171 Angler 135 Black Max Mercury[br]1987 21b 225 Yamaha[br]1974 23 inboard Gusto gone.[br]1979m21 225johnson \"blue dolphin\" bought off this board and restored [br]with everyone\'s help!!Gone but not Forgotten....[br]1979 20 Mako 115 Suzuki gone[br]1977 19 Mako 115 Johnson gone[br]1976 23 Mako twin 140 Johnsons gone[br]1983 224 with closed transom and bracket[br]And 162 SOB (some other boats)[br]Venice Florida, Traverse city Mi.

              Comment


              • #8
                OK, I will order a timing light today, and get to work on link and sync! Always something new on outboard engines.

                Thanks!
                Mark Kriz[br]Mako15 1974[br]Mercury Thunderbolt 800 1972[br]Maple Valley, WA[br][br]

                Comment


                • #9
                  harbor freight has them for 25 or so....
                  [br]1994 Mako 215 Dual console Optimax 225[br]1978 Mako 19 with 90hp johnson[br]1996 Mako 22[br]1982 Mako 171 Angler 135 Black Max Mercury[br]1987 21b 225 Yamaha[br]1974 23 inboard Gusto gone.[br]1979m21 225johnson \"blue dolphin\" bought off this board and restored [br]with everyone\'s help!!Gone but not Forgotten....[br]1979 20 Mako 115 Suzuki gone[br]1977 19 Mako 115 Johnson gone[br]1976 23 Mako twin 140 Johnsons gone[br]1983 224 with closed transom and bracket[br]And 162 SOB (some other boats)[br]Venice Florida, Traverse city Mi.

                  Comment


                  • #10
                    I got a nice one at Autozone, it does 2 or 4 stroke and shows the RPM as well, so you can also verify your tach. But it was $100 and at that price, you may as well drop the Mer off at a shop and have them look at it for an hours worth of labor.

                    Your RPMs are so off, it almost seems you're down a cyl. Do a drop test like Dave said..
                    [br]Michael R. Delgado[br]1972 Mako 22[br]http://classicmako.com/forum/topic.asp?TOPIC_ID=15745[br]1976 Mako 25[br]http://classicmako.com/forum/topic.asp?TOPIC_ID=18013&SearchTerms=mako,25[br]

                    Comment


                    • #11
                      Hi everyone,

                      So I have discovered I am an idiot (in computerize I committed an ID 10T issue). Took the Mercury apart again last evening, TDC is lined up and correct for the piston, the timing mark, and the distributor. Decided to check the throttle, and found the butterfly in the carb is opening 2/3 to 3/4 of full open, I have at least another 3/8 inch that the throttle can open, so the throttle cable isn't traveling as far as I need it to. Reverse, however, opens full!

                      Anyone know if it is the throttle cable that needs adjusting? Is it the throttle box and handle?

                      I'm just happy to know the engine is doing what it is adjusted to do. I would assume if the throttle opened full I would be in the 5000 rpm range.
                      Mark Kriz[br]Mako15 1974[br]Mercury Thunderbolt 800 1972[br]Maple Valley, WA[br][br]

                      Comment


                      • #12
                        You should be able to adjust the throttle cable at the engine side to get your full forward throttle. Sometimes the plates dont absolutely open flat but thats ok...

                        dave
                        [br]1994 Mako 215 Dual console Optimax 225[br]1978 Mako 19 with 90hp johnson[br]1996 Mako 22[br]1982 Mako 171 Angler 135 Black Max Mercury[br]1987 21b 225 Yamaha[br]1974 23 inboard Gusto gone.[br]1979m21 225johnson \"blue dolphin\" bought off this board and restored [br]with everyone\'s help!!Gone but not Forgotten....[br]1979 20 Mako 115 Suzuki gone[br]1977 19 Mako 115 Johnson gone[br]1976 23 Mako twin 140 Johnsons gone[br]1983 224 with closed transom and bracket[br]And 162 SOB (some other boats)[br]Venice Florida, Traverse city Mi.

                        Comment


                        • #13
                          I found it!!! Why the throttle was not opening up to full! The throttle connection was upside down, so it was hitting the shift linkage bolt below it. Movement was restricted t0 3/4 throttle. I'm about to take the boat out and check for WOT, rpms, and mph. I bet I get the 5000 or so I am supposed to!
                          Mark Kriz[br]Mako15 1974[br]Mercury Thunderbolt 800 1972[br]Maple Valley, WA[br][br]

                          Comment


                          • #14
                            Thought I would let everyone know, over 37 mph in the Mako 15 is way to fast for me! 30 mph is about as fast as I ever want to go. I cut the throttle back after going above 4200, wasn't watching the tach much after that, but 4000 rpms was 30 mph. I didn't want to keep going faster to find the WOT rpm. So I think the problem is solved!
                            Mark Kriz[br]Mako15 1974[br]Mercury Thunderbolt 800 1972[br]Maple Valley, WA[br][br]

                            Comment


                            • #15
                              Awesome!!!! yes at 40mph things start going by pretty fast in a boat...especially a 15 footer....LOL...enjoy.

                              dave
                              [br]1994 Mako 215 Dual console Optimax 225[br]1978 Mako 19 with 90hp johnson[br]1996 Mako 22[br]1982 Mako 171 Angler 135 Black Max Mercury[br]1987 21b 225 Yamaha[br]1974 23 inboard Gusto gone.[br]1979m21 225johnson \"blue dolphin\" bought off this board and restored [br]with everyone\'s help!!Gone but not Forgotten....[br]1979 20 Mako 115 Suzuki gone[br]1977 19 Mako 115 Johnson gone[br]1976 23 Mako twin 140 Johnsons gone[br]1983 224 with closed transom and bracket[br]And 162 SOB (some other boats)[br]Venice Florida, Traverse city Mi.

                              Comment

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