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Thread: Number of 20H conversion exhausts

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  1. #1
    Sam Cullis Mark75H's Avatar
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    Default Number of 20H conversion exhausts

    A question about the number of 20H conversion exhaust towers made came up on another forum and I think it is probably an interesting question. Some people might try to convince a prospective 20H buyer that the conversion exhaust tower is rare. Compared to 50hp fishing motors, it is ... compared to Sorianos or Mark75H's it is not.

    As an educated guess I would say at least 1,000 conversion towers are made and sold maybe as many as 2,000, but probably not 3,000 based on the fact that 4,000 20H's were made and not all of them were converted.

    The conversion kits came out in the summer of 1959 more than 3 years after the end of production of 20H's. 1958 and 1959 were 2 of the all time peak years for APBA Stock Outboard racing. By 1961 the numbers of racers began to dramatically decline and never rebounded to the late 1950's peak.

    The factors involved in this are probably:
    -General recession in the economy
    -Change in management at Hearst Newspapers
    -Lack of availablity of new racing motors at dealers
    -Having to buy the conversion kits and a new prop to stay
    competitive in the B classes. (Quitting or spending that extra money
    probably caused a lot of racers to drop out at a time when things
    weren't going that well anyway.)

    A fully converted 20H would have the exhaust kit, carb kit and gear kit
    along with 55H-1 style pistons and a different prop. Each of these
    things was sold separately and I have never looked into the exact total
    cost, but it may have been half the $400 price of a 20H when new if
    you had to pay labor. My dad was the highest paid mechanic in our
    area back then and only brought home $20 a week.

    A look at the numbers of racers registered to race in the B classes in an
    early 1960's year would probably be another reflection of how many
    were converted. It would show a minimum but not be accurate on the
    top because of these factors:
    -Some racers raced runabout and not hydro and vice versa, some raced both
    -Not all racers raced APBA
    -Not all racers raced every year
    -A few people raced with uncompetitive unconverted motors just for
    -A very few racers used Champion Hot Rod motors

    If my memory is right, there were 700 to 900 or so racers running in
    each of the B classes in APBA thru the early 1960's. This brings us full
    circle to the 1,000 minimum conversion exhaust kits estimate.

    A few years ago I started wondering about the Mk30H style long skegs on the later 20H's. It looks like about the last 1/4 of 20H's had the long skeg lower unit ... also about 1,000.
    Last edited by Mark75H; 07-18-2007 at 11:31 AM.
    Since 1925, about 150 different racing outboards have been made.

  2. #2
    Sam Cullis Mark75H's Avatar
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    Default 20H's delivered converted

    The conversion kit came out in the summer of 1959, about 3 years
    after the last Mk20H left the factory, so no 20H's came from the factory
    converted ... that is why it is the "conversion" kit ... all were field

    20H's were made in one run actually during 1954 & 55 calendar years, some sold as new 1956 motors, though they were made during 1955. Late in calendar year 1955, all 1956 models were in production, including the Mk30H.

    Confusion arises because some distributors overstocked on 20H's in
    1956 and still had new ones to ship to dealers as late as the early
    1960's. Same thing with dealers, some bought too many and had them
    on the floor for years.
    (We are probably only talking about 200 or fewer of the 4,000
    maybe only a few dozen)
    A customer could have bought a new 20H from
    an overstocked dealer and had it delivered converted anytime after the
    summer of 1959, but it did not come from the factory that way. It
    could have even been converted at the distributor (for extra charge)
    and shipped to the dealer already converted or done at the dealer.

    During this time period, the distributors were little more than "super
    dealers" not the faceless warehouses that came later and most still had
    mechanics working in a shop. Later, the shear volume of distribution
    caused most of them to drop their shops and even local dealerships
    because of the money they were making being the wholesaler.

    The same situation arises with a few distributors that would install
    Speedmaster racing lower units on 6 cylinder Mercs before shipping
    them to the dealer. No 700's, 800's, 850's or 1000's were equipped
    with Speedmasters at the factory, but an agreeable distributor
    sometimes did it for a dealer and it would arrive at the dealer
    equipped. The distributor would probably keep the gear shift lower unit
    even after charging the whole price for the motor, and have the
    gear shift unit available to sell as a replacement unit.
    Since 1925, about 150 different racing outboards have been made.

  3. #3
    Team Member Tim Chance's Avatar
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    Another factor to consider on the conversion of stock 20H's is that a lot of them were already converted, converted to alcohol. Plus many of the conversion housings were made into fuel tanks by Quincy Welding.

  4. #4
    Sam Cullis Mark75H's Avatar
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    Those certainly were uses of the conversion tower, but I would use the word "some" rather than "many" or "a lot". To me, "many" and "a lot" implies something like half or more - even if it doesn't exactly mean it.

    In the world of eBay & AOMCI, very few 20's converted to alcohol turn up, but the volume of stockers is high. I have a block converted to use alcohol and know of a few people who have others including complete motors. I think I have seen 2 or 3 of the Quincy converted tank units.

    Neither of these uses would have dramatically reduced the stockpile of conversion towers which is what this discussion is about.
    Since 1925, about 150 different racing outboards have been made.

  5. #5
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    Default 20h

    Sam: Thanks for the interesting info as I always wondered about some of those details as I ran a 20H Conversion back then. Regards John Lawrence

  6. #6
    Sam Cullis Mark75H's Avatar
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    Default KA2A myth

    There is another persistant myth that KA2A carbs were supplied in place of KA7A's in some circumstances.

    I find even the idea of this silly. KA2A's were never approved as a replacement part on 20H's or 55H's. Any racer who bolted on a KA2A would risk certain disqualification.

    KA2A's were very similar to KA7A's with one imporant difference:
    KA7A's were designed to be a direct replacement for the Carter N used on the 20H and 55H -and- the Carter N series has a slightly wider mounting flange. The carb mounting studs on the front of 20H's and 55H's is wider than the stud spread on the Mk28/Mk58 and subsiquent Merc's using KA carbs.
    Since 1925, about 150 different racing outboards have been made.

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