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1992 Plastic Topped 15hp Carb vs 1982 All Metal Carb

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  • 1992 Plastic Topped 15hp Carb vs 1982 All Metal Carb

    Aside from the design, is the performance of the later model 9.9/15 hp OMC carburetor identical to the earlier models which are all metal? I have a 1992 9.9 Johnson which has a 15hp carb of the same year on it....when I got the motor it ran great but never idled well. Found out it had 1993 or newer plastic top on it and had been rigged up so that it functioned like the 1992 model one by being able to work the low speed mixture needle through the front of the cowling. I replaced it with the appropriate year plastic top along with a new needle. It idles down better but is still doesn't get as low and smooth as I would like. Maybe it just needs a good cleaning.

    But to the point of the post, I also have a 1982 15hp Evinrude which idles down great and I was wondering if I could just swap the two and have no performance change in terms of max WOT rpms. I know these two models are virtually identical but have no idea if the carbs have the same throat size and jetting. I plan on selling the 1982 model soon so I would hate to sell off a carb which I consider a better design. I'll prob swap the carbs and lake test it myself but I was curious to what others on here thought about this.

    BTW, the 1992 model has good compression and spark and I have decarbed it recently as well. I'm sure it just needs some super tiny orifice cleaned but I do think the older design is superior and worth keeping over the plastic topped one.

  • #2
    I don't know if there is a performance difference between the plastic topped carbs and the older style. I know from experience the plastic tops on these 25 yr old motors can break. Early plastic tops used a screw to attach the cam follower, and the plastic assembly apparently could develop stress fractures -- know my '91 recently broke, and I repaired it with epoxy and a tiny screw (depends on where it breaks, I'm sure). So far, it's holding. A new/NOS replacement top goes for $90. The later model went to a plastic post built into the top, rather than a shoulder screw for the cam follower.

    That aside, I got improvement by going back through the carb and giving it another cleaning. In particular, I used soft wire to clean the idle tube and the orifice in the nozzle well (removed and cleaned the little jet -- came out very easily, so might have been set in slightly too loose). Think that did it, as the motor immediately settled down and idled properly -- burns absolutely clean and smoke free ('91 9.9 Johnson, E10EEIR). I also changed out the cover gasket for what might be the proper one -- black, with a notch or cut out at the cam follower screw. (The other two in the kit are brown, and the configurations are slightly different -- including the one I had in there). The top using the cam follower screw has a hump where the screw is inserted, and I think the notch is supposed to lay up around the hump.

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    • #3
      those metal carb works better. you can switch carbs with no problem.
      but remember that idle depends also with compression. if compresion is higher then motor can stay with low rpm becouse have enough power to suck air/fuel mix from the carb

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      • #4
        Thanks guys. I believe I will swap the carbs out and give it a test run and see how my WOT rpms change, if any. And while the carb is off go through it and see if I can't clean it a little better. When all is said and done, if the old style gives me equal performance I likely will keep it as I plan to keep this little motor as long as possible.

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        • #5
          I work on an run a lot of these motors. Probably 30 of them in the last 2 years. I am on the fence of old vs.new. I like the idea (theory) of the plastic top as they are more easy to clean they claim. The old lower compression ones seem to idle best, so slow you can see the letters on the top of the flywheel I always say. Few know that in the mid 80's they produced some with 7000 rpm. These are great motors. I like the later models coz they have the kill switch and cable throttle link. But the old ones are great too, just got in a "76" today. Funny as I had the same question as to swapping, glad you asked. The old ones tend to have the tiller arm, pull start assembly and shift lever broken or jacked around. The motors hardly ever seem to wear out and run well with low compression. One of the best!

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          • #6
            Originally posted by thatone123 View Post
            I work on an run a lot of these motors. Probably 30 of them in the last 2 years. I am on the fence of old vs.new. I like the idea (theory) of the plastic top as they are more easy to clean they claim. The old lower compression ones seem to idle best, so slow you can see the letters on the top of the flywheel I always say. Few know that in the mid 80's they produced some with 7000 rpm. These are great motors. I like the later models coz they have the kill switch and cable throttle link. But the old ones are great too, just got in a "76" today. Funny as I had the same question as to swapping, glad you asked. The old ones tend to have the tiller arm, pull start assembly and shift lever broken or jacked around. The motors hardly ever seem to wear out and run well with low compression. One of the best!
            Yes, I love my 1992 model for the reasons you stated regarding the cable throttle system and the kill switch location. Only thing I would also like is a frontward mounted shifter like the 1993 models and newer have. I have actually contemplated rigging one up on my own somehow.

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            • #7
              scout-j-m,
              I was just curious if you ever had a chance to swap these carbs around. I am looking to swap the carb on my 1987 Johnson 9.9 with the plastic top carb to a 15 hp for some extra power. I wasnt sure whether i could put a 15 hp carb on with the metal top or if I had to find one with the plastic top.
              If your swap worked I am sure mine will too.
              Thanks

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              • #8
                Originally posted by FiBerOpTiK View Post
                scout-j-m,
                I was just curious if you ever had a chance to swap these carbs around. I am looking to swap the carb on my 1987 Johnson 9.9 with the plastic top carb to a 15 hp for some extra power. I wasnt sure whether i could put a 15 hp carb on with the metal top or if I had to find one with the plastic top.
                If your swap worked I am sure mine will too.
                Thanks
                Unfortunately no. Im not sure I have even been out in the boat since posting that since I have been so busy. I plan to go out this weekend though so maybe I can try the swap then.

                Comment


                • #9
                  Originally posted by scout-j-m View Post

                  ... Only thing I would also like is a frontward mounted shifter like the 1993 models and newer have. I have actually contemplated rigging one up on my own somehow.
                  Just a historical note: There was a '50s or '60s version of front shift controls -- shifting was done by pulling or pushing the tiller handle, while allowing the twist grip to continue to work as a throttle. I had one fifteen or twenty years ago, and sold it with a bunch of other antique marine stuff. I think I hooked it up to see if it worked (it did).

                  Probably others floating around at garage sales and eBay -- so will just mention it.

                  Comment


                  • #10
                    Sign up today
                    Originally posted by scout-j-m View Post

                    Unfortunately no. Im not sure I have even been out in the boat since posting that since I have been so busy. I plan to go out this weekend though so maybe I can try the swap then.
                    When you get a chance to swap them out can you post and let us know how it goes? I'm curious to know.
                    Thanks again

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