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Mercury 25XS Query

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  • Mercury 25XS Query

    G'Day all. I picked up a first gen 25XS for my restored Bezoat shovel. This is one of the long shaft motors made in 1985 and 1986. As far as block identification goes, there are no serial# tags, but there is one stamped into the intake plenum, port side. 85A006. 1985, RevA , #006?. There is also a name scratched into the plenum, Starboard side. T. Good. Does that ring a bell.?
    Overall, the engine is in decent shape. Good compression. Smooth bearings. Does not appear to be spark though. I'll have to dig a little deeper. Will any year CDI work on this? Or are they XS model specific. I have a couple in stock (I never throw those out) for my fishing motor.
    Another thing I noticed is there is no timing advance linkage. It is fixed directly to the block via an adjustable link. Weird.
    Anyhow, any info on these motors would be helpful and of interest.


    Tom 1985 25XS brochure.JPG

  • #2
    Tommy Good from Massachusetts and South Shore Outboard Association. Top notch driver with many championships.
    444-B now 4-F
    Avatar photo credit - F. Pierce Williams


    • #3
      Howie. Thanks for that info. I'll see if I can track him down. Maybe get a story or two.


      • #4
        TomSki, I think you nailed it except for "Rev A"... 1985 engine and #6 production engine. Pretty cool find, BUT it isn't real until you post some pictures!
        It will be a super fast boat with that engine, so wear a helmet and good life vest and be sure to have a chase boat in the water to assist for at least the first few trial runs. You would be in a bad situation to wreck that boat without anyone around.

        The first generation 25XS should have a chrome bore block and I think it should not have a thermostat in the waterjacket cover. And the throttle cable goes straight in the front of the cowl to pull directly on the carb butterfly shaft.

        I owned the second to last (still) and the VERY last 25XS engines sold by Mercury Performance Products. Dave Young, Jr runs the last one sold and the van Weele Bros have the second to last one sold as far as I know. The last one was a way different engine than the one you just got. I have a NOS tower & adapter and a NOS 25SS gearcase hoping to build a likeness of the first generation 25XS engine one day.
        Attached Files


        • #5
          20201111_170511.jpg 20201111_170456.jpg


          • #6
            Great info 25XS! I love the short version XS as well. They are just badass!. I'm going to assume you know where to source any parts I may need.
            Any tips are welcome as well.
            A couple of pics for ya. The cowlings are currently off. If it wasn't such a nice looking motor, I would leave them off.


            • #7
              Originally posted by TomSki View Post
              I'm going to assume you know where to source any parts I may need.
              Your gearcase isn't the early one I expected to see... Doesn't look like a 25SS, rather it appears to have a larger, swept skeg. Can you post a profile pic of the gearcase? Your gearcase, exhaust tower, and adapter/tuner plate are unique and "unobtainium" parts. They rest is pretty much 'fishing motor' parts.


              • #8
                20210213_183603.jpg 20210213_183612.jpg Ok, the plot thickens. Upon looking at the photos I just snapped, I noticed a crack on the bracket where the previous weld is.
                Ran out to the garage to investigate. Yup, there is indeed a crack, as well as a matching one on the other side. The serial number on that bracket is 780009.
                at very least, that bracket was replaced with the older one from 1978. Looks like I've got some fixing to do. It is possible just the bracket was replaced. They were prone to failure.
                The gear case does not match the one in the brochure picture for sure. It is all metal with no bondo or visible welds. The dapter plate is cast piece and looks to be the proper Merc unit. I do have the rear gear case cone fyi. 20210213_183637.jpg


                • #9
                  Ok, no big deal; your engine has the more common 1986-92 gearcase for the 25XS with the "crescent leading edge" or CLE (the swept up profile from the front tip of the gearcase up and back to the top of the gearcase leading edge).
                  Your original 25XS engine uses the Merc200 transom swivel bracket and clamps from a fishing engine earlier than the 1981 Mercury 18/25hp "looper" piston design engine that is mounted on top. That is why the special adapter/tuner plate is required. It adapts the flat top piston (looper) engine to the older Mercury 25SS exhaust tower & gearcase.