IN THE BEGINNING...The first Mercury racers were just stock fishing engines.About 1950, Merc
introduced the quicksilver lower units.Seeing a need for true race engines,they
introduced the KG-4H and the KG-7H. Sporting their pretty green tanks and silver lower
ends. These engines got a lot of guys started into racing. Being both affordable and
reliable, many people were finally able to enjoy a sport that before the late 40's was
only for the few. Serial number ranges for the motors are:
IS THAT LEGAL ? These engines and drivers were very competative. Large numbers of boats and drivers would show up at every race. Many tricks were tried to hop up the motors and hopefully get that first place trophy.Trying to get by the inspectors was a real challenge that normally failed. Here's a few parts that were built for add on HP.Read about some modifications . Click here.
LET'S GO FASTER! 1954..Merc rolls out their new class B racer...the MARK 20H. Speculation was all over the place.Was this motor gonna cream the KG-7's?...or was it just a new paint scheme for the year? Boat Sport magazine put out an article October of that year, "TESTING THE MERC 20H". Running 2 exact boats, one with a KG-7H, one with the 20H,they found that the 20H was about 4-5 MPH faster.Merc really did their homework.This motor was here to stay.Click for the on this engine. There are some really great articles on the 20H . Click here to read. Serial number range was from 786613 to 790612.
BUILT FOR SPEED...The 20H was a really unique engine. Kind of a cross between the MK20 and the MK25.Add a big carb and a few years of experience in making KG-7's go fast, and there you have it. Here's some photos comparing the parts between the three engines.Mk20 on the left,20H middle, MK25 on the right.
WOW....WHAT THE HECK IS ALL THAT NOISE?
Then one day along came this blue engine called a HOT ROD. Merc was not going to stand for another brand of engine kicking their butts. They tried all kinds of ways to make the 20H go faster. Finally they found the secret. A tuned pipe system.Merc sent Jack Leek a welded up sheet metal prototype to try out. He grabbed Billy Schumacher and his Hot Rod and they went out testing. They found that the Merc was faster and another page of history was born....The 20H conversion...toilet bowl...cornpopper ...whatever you want to call it. Permanent hearing loss. Read about the conversion kits. Click here.
The conversion kit came in three sets. The first was the carb conversion. It changed the Carter over to a Tillotson KA7A and also added a fuel pump.(getting rid of the pressure system two line setup). Next was the tower housing,filler block and elbow.Finally a 16:21 gear set for the lower unit and you were in business. Timing was kicked back from .375" btdc to .235" btdc. All this added up to another 5 MPH. Not too shabby!