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1952 Mercury KH7 outboard engine

R

Ram Jet

Contributing Member
I just bought a 1952 Mercury KH7 outboard. I'm waiting for some special tools to remove the flywheel and water pump impeller. Has anyone had any experience with this engine? Anything I should look after - heck, it's only 66 years old, what could go wrong. I think I may have posted something like this post before. If so sorry.

Thanks in advance,

Bill Albertson
Burtchville, Michigan
 
The gear box is a bit weak, and SOME early ones had an impeller that was too small. When you get it apart, let me know and I'll post a photo of the correct impell0er to compare with.

Plan on changing all of the lower unit seals.

Jeff
 
fastjeff said:
The gear box is a bit weak, and SOME early ones had an impeller that was too small. When you get it apart, let me know and I'll post a photo of the correct impell0er to compare with.

Plan on changing all of the lower unit seals.

Jeff
Click to expand...

Hey Jeff,

Thanks for your feedback. I know about the overheating problem. In fact I'm on the phone right now with Mercury Marine trying to get any info I can. Well, off the phone. A gal named Krissy tried to help and she had me on hold for about 5 minutes. No luck and no information is available. Well, now I know. I'm on my own. I ordered a flywheel nut removal tool, a replacement choke knob, carb rebuild kit, water pump impeller removal tool, eBay repair manual and a 1 3/8" socket to remove the fuel filter. As far as the gear case is concerned I drained out the old gear case oil and installed Quicksilver Premium S.A.E 80W-90 gear lube. It's been over 48 hours and there are no leaks from the gear case. I did pour about 1/4 of a quart of Mobil 1 synthetic type A transmission fluid into the intake port and turned the engine upside down and hopefully the con rods and wrist pins got oil. I didn't want a "dry start" as this engine has not been run in over 30 years. The recoil starter is a-bit mucked-up but I think I can fix it. The ATF ran out of the lower unit so I assume the bottom crankshaft seal is toast. I'm happier than a pig in poop to have gotten this little engine. It's been a part of my life for a long time. I rebuilt a Mark 20 when I was about 16 (I'm 70 now) and ran it on a Popular Mechanics boat called a Minimost. I made it 7' feet long (it was supposed to be 8'). I remember that when I hit the throttle that little boat leaped (literally) out of the water. I'm installing this KH7 on a 1975 12' aluminum boat. I have a feeling this rig will rock and roll. The Sears boat is very much like a Penn Yan Swift and that boat flew with a 20 C.I. Yamato racing engine. Jeff, if you can hook me up with a Quicksilver lower unit I would be grateful.

In a holding pattern waiting for my tools. Oh, by the way, the magneto is working fine. I wired-up the plugs to ground and pulled the engine over. Big blue sparks arched across the plug electrodes. I purchased NGK B6S spark plugs (I don't care for Champion plugs anymore).

I'll let you know if I can bring this old clunk back to life.

Cheers and thanks,

Bill Albertson
Burtchville, Michigan
 
Perhaps intake and exhaust ports were open and oil went right through.----No need to jump to conclusions about a lower seal.-----But 60 year old motors do benefit from new seals !!!----The KG7 version had more power than KH7 model.
 
racerone said:
Perhaps intake and exhaust ports were open and oil went right through.----No need to jump to conclusions about a lower seal.-----But 60 year old motors do benefit from new seals !!!----The KG7 version had more power than KH7 model.
Click to expand...

What mods were made to the KG7 that hopped it up? Bigger carb venturi? Hmmmm. I'll keep an eye on the gear case seals. I change gear case oil at least annually so I'll be aware of any water infiltration.

Thanks again,

Bill
 
racerone said:
Perhaps intake and exhaust ports were open and oil went right through.----No need to jump to conclusions about a lower seal.-----But 60 year old motors do benefit from new seals !!!----The KG7 version had more power than KH7 model.
Click to expand...

Me again. Yeah, I thought of that. Maybe the ATF ran right through the transfer ports and out the exhaust. I freakin' hope so. When I get all my special tools I'll stick the KH7 in my 20 gal. garbage can and see If she fires-up. Fingers crossed.

Cheers,

Bill
 
I'd replace the upper and lower crank seals right away. Both come out without having to split the cases.

On hopping her up--many have added a larger carb with little improvement. Going to a Mark 25 of Mark 28 powerhead is the best improvement you could make.

Jeff

PS: Those Cruisers are neat, special Mercs.
 
fastjeff said:
I'd replace the upper and lower crank seals right away. Both come out without having to split the cases.

On hopping her up--many have added a larger carb with little improvement. Going to a Mark 25 of Mark 28 powerhead is the best improvement you could make.

Jeff

PS: Those Cruisers are neat, special Mercs.
Click to expand...

Thanks Jeff. I think I found a source for the seals. I'm glad I don't have to split the crankcase. I do think the rings are tight. With that ATF in the cylinders it's a bear to pull over. Yeah, this little engine is nice - I'm in love again. Just like a woman - money, money money. Whew!

Again thanks.

Bill Albertson
 
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