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Johnson late 90's difference between 15 and 9.9

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  • Johnson late 90's difference between 15 and 9.9

    Hello--
    I've searched through the threads and didn't see information on this and have tried a few google searches without success. Does anybody know the actual thrust/power differences between a 15 hp and 9.9 hp late 90's (looking at a 1998) outboard? I was told recently that the specs are basically the same and am looking to verify. This will go on a 12 boat that currently is running a 15 HP 1984 evinrude and i'm looking to increase power and reliability with a new(er) motor. Thanks in advance for any help

  • #2
    The newer 9.9 has more displacement.----The newer motors have many parts that are different.------Cowlings / recoil starter / linkages.-------The lower unit fits from 74 to 2007.------Crankshaft / rods are the same.-------In my opinion a 1984 is a wonderful simple motor !-----Nothing wrong with the reliability of an 84 model if it has maintained.

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    • #3
      thanks for the note and comments. the 1984 is on a boat with a deck on the stern which makes it awkward to reach the gear shift so I've been looking to move to a forward facing gear shift. And recently, it's struggled to reach its former top end speed. I have not put a tach on it (don't own one and can't find one to borrow or rent) and it just doesn't sound like it's reaching its former WOT rpms. I've been over it and can't seem to find an issue. Next step if I stay with it would be to swap props around. Open to any ideas! thanks again

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      • #4
        Swapping props won't help " revive " a motor.----Do some trouble shooting.------Post the compression numbers here.----And have you installed a new impeller on the water pump at some time ?-----Could be a pin hole in the fuel pump diaphragm too.----That is easy / cheap to inspect and new diaphragm is just a few $.-------I have many of these older 9.9 / 15 for parts / rebuilding.-----Last one I got cheap was a 1992 model with spark and compression issues.----Easy fix for me.

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        • #5
          thanks for the help. I don't have the motor to hand (off with the boat at another location) so I'll have to get back with you. I replaced the water pump last year. I did a rebuild of a 1987 evinrude 15 this winter as a way to learn as much as I can about these motors. (that motor is still on the cart and not running!) and I have a million spare parts, including a couple fuel pumps.

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          • #6
            Originally posted by Jamoose View Post
            thanks for the note and comments. the 1984 is on a boat with a deck on the stern which makes it awkward to reach the gear shift so I've been looking to move to a forward facing gear shift. And recently, it's struggled to reach its former top end speed. I have not put a tach on it (don't own one and can't find one to borrow or rent) and it just doesn't sound like it's reaching its former WOT rpms. I've been over it and can't seem to find an issue. Next step if I stay with it would be to swap props around. Open to any ideas! thanks again
            did your issues show up after adding the deck?
            Cheesehead boating the Gulf Coast of FLA 27.51° N, 82.53° W

            1988 Cruisers Rogue 2420 -VP 290 DP now powered by custom 468 - https://forums.iboats.com/forum/owner...988-rogue-2420

            Past Boats
            1970 Wooster Hellion - Merc 9.8
            2002 SeaRay 190BR - 5.0 - A1G2 - "Cheeseheads in Paradise"
            1984 Avanti 170DLI -3.0 stringer- "Ship Happens"

            What’s behind you doesn’t matter.Enzo Ferrari

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            • #7
              ??----Well I would fabricate a bracket and some sort of handle to get the shift within easy reach.

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              • #8
                well, now that's a great idea!

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                • #9
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                  Originally posted by Scott Danforth View Post

                  did your issues show up after adding the deck?
                  they did not. The boat is a barnegat bay sneakbox that i use for duck hunting and the stern deck has always been there.

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