25HP...VARIES WITH RPM
Yeah, sure. Well, looks like Merc outdid theirselves
this time. If 2 cylinders were good, why not build a motor with 4? The early KF-9, KG-9
and Mark 40 were all very cool engines. These motors outran the competition hands down.
Add a Quicksilver lower unit and voila, you've got yourself a Class D racer. This early
four cylinder reigned supreme until 1956....then along came trouble.
Serial number ranges are:
Mk40H 712900 to 713399 and 825418 to 825917
MARK 30H & MARK 55H....1956
As time progressed, so did the technology.Merc had a
few years of 4 cylinder practice under their belt and introduced two new race engines. A
new 30 cubic inch racer, the Mark 30H, and the opened up and improved 40 c.i. Mark 55H.
The 30H powerhead was the same as the fishing model except for a light flywheel. The 55H
had it's own unique block and carbs. As with the 20 H, the 55H came equipped with Carter
N carbs.The same problems occured with this motor and most were
eventually converted to Tillotson KA7A's. The early 30H came with sunset orange cowls. The
early 55H was dark metallic green. They made later versions of both engines with the more
square white cowls and chrome bands.
Serial number ranges are:
MK30H 997920 to 999919 and 1166471 to 1166568..with some others up to 1260724
MK55H 983920 to 984919 and others 1260725 thru ?
pics of the original Carter Carb setup on the 55H
ALKY + NITRO = BOMB So , here's what happens when
guys wanna blow their eardrums out.Guys like Quincy and a few other fellows really came
out with a lot of innovations that the factory stole back and incorperated into the new
engines on the market today....well...maybe not the pipes.