Number of 20H conversion exhausts

[Mark75H]

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
fun
-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.

[Mark75H]

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
converted.

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.

[Tim Chance]

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.

[Mark75H]

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.

[john lawrence]

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

[Mark75H]

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.

[mercguy]

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.

I find it hard to believe also Sam. The choke setup on the KA2A is different also and would not allow the lever (if able to mount) to clear the cowl on the stocker........the closest match to the KA7A is the KA5A, which uses the same style choke and lever assy, but this carb came out after the 7A's.......

as it is though, both the 2A and 5A would require the mounting holes/Flange to be hogged out to fit the wider 20H carb opening of the Carter.