1973 johnson 50hp outboard

[kjones]

I have a 14ft aluminum bow rider boat with a 1973 50 hp outboard engine. I am running a 15 pitch prop on the boat. when I have 3 people in the boat it has a hard time to plane out. it will eventually plane out after a few hundred yards. I recently changed from a 17 pitch prop to a 15 prop. it didn't really make a difference. I have good compression in both cylinders. once the boat does plane out it goes approx. 28 mph with the 15 pitch prop and I can get 34 with the 17 pitch. no idea what the RPMs are as I do not have a tach. I am looking for more hole shot power and am unsure where to look for this. I want to pull a tube but am unable to plane the boat out with a tube on back. the boat is light and I can move it around by myself. I would think the 50hp should push it fine. the boat itself is only rated for 55hp. like I said one it planes out it runs great. when by myself It will plane easily and runs great.

let me know your thouhts on this.

thanks

[Joe Reeves]

Three things we need to know........

With both s/plugs removed... what is the psi compression reading of both cylinders?

Plugs still removed... The spark should jump a 7/16" gap with a strong blue lightning like flame... a real SNAP! Does it?

The spark plugs should be Champion plugs gaped at either .040 (strong spark) or .030 (longer life). Are they?

(Spark Tester - Home Made)
(J. Reeves)

You can use a medium size philips screwdriver (#2 I believe) inserted into the spark plug boot spring connector, then hold the screwdriver shank approximately 7/16" away from the block to check the spark or build the following:

A spark tester can be made with a piece of 1x4 or 1x6, drive a few finishing nails through it, then bend the pointed ends at a right angle. You can then adjust the gap by simply twisting the nail(s). Solder a spark plug wire to one which you can connect to the spark plug boots, and a ground wire of some kind to the other to connect to the powerhead somewhere. Use small alligator clips on the other end of the wires to connect to ground and to the spark plug connector that exists inside of the rubber plug boot.

Using the above, one could easily build a spark tester whereas they could connect 2, 4, 6, or 8 cylinders all at one time. The ground nail being straight up, the others being bent, aimed at the ground nail. A typical 4 cylinder tester follows:

..........X1..........X2

.................X..(grd)

..........X3..........X4

Thousands of parts in my remaining stock. Not able to list them all. Let me know what you need and I'll look it up for you. Visit my eBay auction at:

joe_omc32 | eBay
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