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Results 1 to 10 of 10
  1. #1

    Default Mercury 6hp to mercury 15hp foot swap?

    Hello everyone my name is adam, I've got quite a dilemma. I have recently broke my crankshaft bolt on my 1997 mercury 2 stroke 6 horse, so id consider it totalled from my research. Last weekend I picked up a 1989 mercury 2 stroke 15 horse for a very good deal, the only problem is that the foot is completley tore up. The motors seem almost identical in size, weight, and overall dimensions. My question is, would I be able to take the foot off of my 97 6hp and but it on the 89 15 hp with little or no modification? Any advice with help, thank you, Adam

  2. #2
    Join Date
    Oct 2011
    Location
    maplevalley WA
    Posts
    7,855

    Default Re: Mercury 6hp to mercury 15hp foot swap?

    From what I could find using the 1989 6hp and 15hp the driveshaft and gearbox both have different part numbers you can bet the 1997 has different numbers as well. You can do a side to side comparison of the gearboxes pulled but you probably have different gear ratios in the gearbox. If it fits will the 6hp gearbox handle the extra ponies IDK. I would look for a gearbox for the 89 motor I would think you coud find one in good shape for reasonable. Beware of buying a gearbox on ebay I prefer to physically inspect any gearbox before moneys change hands.

  3. #3

    Default Re: Mercury 6hp to mercury 15hp foot swap?

    Quote Originally Posted by kimcrwbr1 View Post
    From what I could find using the 1989 6hp and 15hp the driveshaft and gearbox both have different part numbers you can bet the 1997 has different numbers as well. You can do a side to side comparison of the gearboxes pulled but you probably have different gear ratios in the gearbox. If it fits will the 6hp gearbox handle the extra ponies IDK. I would look for a gearbox for the 89 motor I would think you coud find one in good shape for reasonable. Beware of buying a gearbox on ebay I prefer to physically inspect any gearbox before moneys change hands.
    I've looked for one for sale, and can't find any for the right year. Do you knnow any reputable websites where I might find one?

  4. #4
    Join Date
    Sep 2010
    Location
    ontario
    Posts
    9,686

    Default Re: Mercury 6hp to mercury 15hp foot swap?

    Serial # of the 2 motors are required in order to give a qualified answer !

  5. #5
    Join Date
    May 2007
    Location
    Inverary, Ontario, Canada - The Great White North Eh!
    Posts
    8,485

    Default Re: Mercury 6hp to mercury 15hp foot swap?

    If you are simply swapping the gearcase (leaving your existing leg and water tube in place), then it is a straight swap.

    The gears are the same (2.08:1), the driveshaft is the same, etc, etc.

    The ONLY difference between the pre-95 and post 94 1/2 units was the water tube and the exhaust plate.

    So, if you retain the driveshaft housing and water tube (with the powerhead) of the motor you want to swap with and simply bolt on the lower unit, it will be fine.

    From 1986 to the end of production the 6, 8, 9.9 and 15 horse were identical when it came to the lower units - I have swapped them many times...
    Graham

    A "professional" is someone who gets paid for their work - it doesn't necessarily mean they are good at it :)

  6. #6

    Default Re: Mercury 6hp to mercury 15hp foot swap?

    Quote Originally Posted by galamb View Post
    If you are simply swapping the gearcase (leaving your existing leg and water tube in place), then it is a straight swap.

    The gears are the same (2.08:1), the driveshaft is the same, etc, etc.

    The ONLY difference between the pre-95 and post 94 1/2 units was the water tube and the exhaust plate.

    So, if you retain the driveshaft housing and water tube (with the powerhead) of the motor you want to swap with and simply bolt on the lower unit, it will be fine.

    From 1986 to the end of production the 6, 8, 9.9 and 15 horse were identical when it came to the lower units - I have swapped them many times...
    Thanks a lot partner. So your pretty much saying the whole lower unit switch will work with no modification? The only thing I was really worried about is the water line matching up and the gears being strong enough. but thanks again, I'll keep y'all updated.

  7. #7
    Join Date
    Sep 2003
    Location
    New Tripoli, PA, USA!
    Posts
    12,533

    Default Re: Mercury 6hp to mercury 15hp foot swap?

    Prof Graham strikes again!

    Impressive.

    Jeff

  8. #8
    Join Date
    May 2007
    Location
    Inverary, Ontario, Canada - The Great White North Eh!
    Posts
    8,485

    Default Re: Mercury 6hp to mercury 15hp foot swap?

    Merc certainly didn't retool to make different gear cases or gears for the 6, 8, 9.9 and 15 horse lines. Everything was built strong enough to suit the 15 horse and then bolted on to every other model.

    Initially the 15 horse used a different powerhead (16 cubic inch) while the 6, 8, and 9.9 shared the 12.8 cubic inch model (part way through the 1994 model year they started building the 9.9 on the larger powerhead, with the 6 and 8 continuing to use the smaller one until the end of production).

    They also each had their own carb and exhaust plate (the tube on the exhaust plate dictated to some extent the max horsepower that you could get out of the powerhead - so simply bolting a 9.9 carb onto a 6 horse would not give you a full 9.9 horses - you had to change the exhaust as well).

    Anyhow, 99.9% of all other parts were shared - so the ignition off a 15 would fit a 6 and vice versa.

    Just about every year (or every production run) the parts would get a new number or a variation of the old part number. So you might see something like 323-11158A6 on a 1987 model and then a couple years later 323-1158A21 on a 1992 model, but the parts are totally compatable.

    They did however go to a different exhaust plate/water tube set-up post 1994, and discontinued the older versions. So if you need to replace a water tube on the 86 thru 94 models it's a bit more involved process. The old ones "screwed" on (with a retainer) to the exhaust plate while the new ones simply pushed in with a grommet or keeper - and they can't retrofit to each other, so a new plate was also required for older models. Additionally, the guide hole part way up the housing was now too small to fit the "flare" part way down the water tube - this requires a "re-drill" of the guide hole (which is almost smack in the middle of the exhaust housing - so a very long "installer" type drill bit is required).

    Aside from the water tube issue I have never found any other problems using parts off of the early 2000 models (even) on 1986/87 model motors.

    As long as you use parts from "real" Merc's in the 6, 8, 9.9 and 15 horse class then you should be fine.

    (real Merc's were models actually built by Merc although they were almost entirely assembled from Yamaha mfg parts. There was also a Mariner line built by Yamaha (Yami-Mariners) which were totally different but available in similar horsepowers. Since 2005, outside of the US you can still find 9.9 and 15 horse 2 strokes, but again, these are built primarily by Tohatsu, which also builds all the under 40 horse Merc 4 strokes, and the parts on the Tohat-Merc's look nothing like the older portables).
    Graham

    A "professional" is someone who gets paid for their work - it doesn't necessarily mean they are good at it :)

  9. #9
    Join Date
    Sep 2003
    Location
    New Tripoli, PA, USA!
    Posts
    12,533

    Default Re: Mercury 6hp to mercury 15hp foot swap?

    Poor Carl must be spinning in his grave!

    Jeff

  10. #10
    Join Date
    May 2007
    Location
    Inverary, Ontario, Canada - The Great White North Eh!
    Posts
    8,485

    Default Re: Mercury 6hp to mercury 15hp foot swap?

    Yes, "counter" rotating
    Graham

    A "professional" is someone who gets paid for their work - it doesn't necessarily mean they are good at it :)

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