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Unlocking frozen motor

Jupiter Dinghy

Jupiter Dinghy

Regular Contributor
Tips request to the usual suspects (you know who you are...lol)
What is the best technique(s) you pros are (or were) using in an attempt to unlock a power head that froze after too long a period of immobility?
 
Start with penetrating oil in the cylinders or kerosene/brake fluid/power steering fluid or a mix of any of them. If the crank is seized tear it down.
 
If you can get a hold of one of these screw in compression gauges and an air compressor, you can use 100 pounds of compressed air to force the penetrant into the rusted area. The fitting is a standard 1/4 m and is compatible with the fittings on my compressor. The pressure also puts a heavy down force on the piston (600 pounds on a 3 inch piston) without doing any damage.
View attachment 16412View attachment 16413
 
compression gauge box.jpgcompression gauge.jpg
 
bobbyc said:
If you can get a hold of one of these screw in compression gauges and an air compressor, you can use 100 pounds of compressed air to force the penetrant into the rusted area. The fitting is a standard 1/4 m and is compatible with the fittings on my compressor. The pressure also puts a heavy down force on the piston (600 pounds on a 3 inch piston) without doing any damage. View attachment 16413
Click to expand...

Great tip! I would have never thought of that (and I have all the required elements) thanks Bobby!
 
I was going to take a look and spray oil under the bypass cover (on the port side of motor) which lets you see the pistons from the side.
This part also serves as starter motor mounting bracket on electric start models.
Does anyone know what the purpose of that part is on non-electric start models? And is there a gasket behind it or can I just use liquid sealant to put it back on?

Here is a pic of the part (from an electric start motor):
 
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