Mercury KG-7H question

[kmercury]

Hello,

I recently inherited an old Mercury KG-7H (1952-53?) and would like to get it running. I had hoped to put it on a small fishing boat but after doing some research, I realized this unit was built for racing and speed.

It has spark on both wires and good compression (does 120psi on the bottom and 118 psi on the top sound correct?)

The carb is varnished up so I plan to clean it.

So my questions are:

• How can I check the impeller without taking the prop off and taking the lower unit apart?
• Should I rebuild the carb with new gaskets
• The prop nut is not moving, is there a way to lock the drive shaft in order to take the prop off

Aslo, do I need to check anything else before trying to fire it up?

Finally, if I can get this running, do you have any suggestions of what type of boat I can put it on? I do not wish to race at this point so a nice speed boat type would be great. I am thinking 10 to 16ft, 2 person. I am a tall guy (over 6ft).

Any help would be great!

Thanks

kmercury

 

[Chinewalker]

Re: Mercury KG-7H question

First off, that's a very nice, rare find! It is well worth putting time & money into in order to preserve and maintain it. Compression sounds good, so you're ahead of the curve already!

You MUST replace the waterpump impeller before attempting to run it. Regardless of whether it "looks" good or not. New ones can be had on eBay (search part number 47-20945). The impeller is located behind the cone nut and rear bearing carrier. The cone nut is REVERSE thread. You can make a tool to remove it using some pipe fittings and threaded rods at 180-degrees to engage the holes in the cone nut. The bearings in the rear carrier must be greased regularly. DO NOT over tighten the cone nut as it can split the gearcase.

Carb kit is readily available at NAPA (part number 18-7013) and will have some of the parts you need (gaskets, etc.).

Hold the propeller with a gloved hand and undo the prop nut. UNDO the spark plug wires before attempting to remove the propeller.

As for what type of boat to put it on, it will be a single seater, no more than 11-feet long, no more than 150 lbs. The motor has 1:1 gear ratio and as such has very little lugging power. Even if you can plane off a larger boat with more than one person the motor will be working very hard to do so and will not perform well. It was designed to rev to 6000+ RPM on a lightweight hull. Set up properly on a good hull it is capable of touching 50 MPH.

As an FYI, if you're looking for less of a lake racer and more general use you can likely sell what you have and buy something more practical and have a good deal of cash left over. True KG7H motors bring a good buck on eBay...