THE BASICS:Here's some photos of the Mercury Mark 75 H (or 75HA as Merc referred to it as). This first set is how they looked,more or less, from the factory in 1957.As the story goes, Merc only put out 25 of these. Sticker price was 1300$.The serial numbers ranged from 75HA1200065 - 75HA1200090. The powerhead is really the most elusive part of the whole engine....when you consider how they were all modified to alky right out of the box.They all came equipped with KA6A Tillotson carbs. the porting and flywheel were the same as the 55H. Reed blocks were close to Mk78's.The parts lists shows that the 2 fuel pumps were actually both run off a special base that bolted to the middle pump outlet. This was supposed to help balance the fuel to the carbs.Included with your new 75H were the tools to disassemble the lower unit, a test wheel, parts catalog and 3 props.
LOWER END:Here's the stuff that makes this engine so neat....the tower and foot.
Going away from the standard Quicksilver lower unit Merc introduced a front loading single
pinion "pre-speedmaster" lower unit.Besides looking a lot different from the
Quickie, this unit also required the tower housing to be complete.All the engines up to
this point had a tower the would join the saddle assy by means of a swivel pin. This unit
did too, but there was only one bushing in the tower..the other was in the foot.There were
replacement service units and towers made for a few years later.This is why there are a
few more than 25 known to still be around.Here's a few pictures of the tower and lower
units. Here are the part numbers for the lower unit and tower. If you look them up in
Merc's "where used" book, They'll say MK75A not H.
VARIATIONS: There were early and late
units.Casting numbers on the housings and water intakes were totally different. The early
units were actually about 3/32" thinner in the torpedo and drive shaft pinion area
than the later. After much use, and being hopped up on fuel, they found that the weak link
was the thin pinion bearing area above the torpedo. Some units failed in this area. Look
for weld marks. You will also see welding on the towers and feet around the 2 rear studs
to help strengthen that problem area.
Another oddball note. Merc toyed with overdrive units as well. Here's one that survived from Lake X.This was when the Starflites had the records.
AFTERMATH:When all was said and done, along came all the modified to alky engines.There were so many different changes and adaptions, not one 75H would look the same. People like Lon Stevens would really get these engines haulin'.Up here in region 10, we're lucky enough to still have about 3 of these motors still raced. No, they're not any competition for the Konigs, but they sure sound SWELL!