Looking for KG-9,KF-9 or Mk.40 information.

[cottonpicker007]

I have been looking for information on these three motors for several years. The KF-9 was introduced in the late 40's KG-9 came next & the Mark 40 around 1950. These were THE performance motors of the day ! 4 cyl. in line, 40 cu.inches disp. Only one gear,forward. They could be very tempermental, so you better have a good foothold when you cranked ! The KF-9 had no recoil starter, had to hand wrap the pull cord around a big fly wheel !
I had a F as a teenager on a 12 ft. ply wood two seater that would run in the 40 mph range ! Flying for that day !
If you have any info or stories about these old Merc's give me a reply. Thank you Guys & I love S & F ! Been a member for years ! Robert Beers

[Tom Foley]

Go on the Racing History forum and look for MK 75 - H a very knowledgeble and connected dude to the older engines . sure miss my 55 - H and 44 - XS engines !

[Mark75H]

The KG9 came with the same open flywheel, the spring recoil starter began as an accessory for the KG9; the Mk40 was the first motor it came standard on.

All these motors were sandcast, preceding the later intricate diecasting on Mercs that decreased costs and increased quality at the same time.

The KF is famous for its bulbous and fragile cast mounting clamp bracket. The KG came with the forged aluminum brackets we are all familiar with.

This whole series of motor use the 4 cylinder magneto popular on many motors during WWII and just after.

The KF and KG ran the mag by what was the then traditional method with those WWII era motors: gears. The Mk40 was Merc's first inline motor with belt driven ignition, replacing the complicated, expensive and noisy gear train.

The early motors did not have the best reputation for durable crankshafts, by the time the 40 came out, the hardening of the crank was greatly improved.

I'll post some stuff about what made them fast in a few days

[cottonpicker007]

Thanks for the reply 75H! Seems like you are very knowledgeable on the old motors. I remember my Dad having a lot of fuel pump problems with his KF 9. It led him to trade it on of all things a 25 HP Jonnyrude !!!

[Mark75H]

The KF and KG had cam operated mechanical pumps, like cars used to have. Without looking it up, I can't say whether the 40 had the cam or diaphragm.