racing engine

[paawe123]

While running my Johnson 1958 10 HP QD-19 the other day I experienced something unusual. I was out fishing and the engine was running perfectly. When I stopped fishing I was running into the launch at full throttle; the engine began to race and it seemed that I lost some propulsion. I slowed the engine and put it neutral. There were a few weeds on the prop so I reversed it and cleaned the prop off. I started off to the launch again and the same thing occurred. On the rest of the way in, I could run the motor at 1/2 to 3/4 throttle and it ran fine but as soon as I went to full throttle the engine would race and I would lose propulsion. After I got home I took the prop off to see if there was anything tangled around it or if something else was wrong; everything appeared in order. Any suggestions or has anyone experienced something similar?

[outbdnut2]

Many props have a thin rubber piece between the hub and the rest of the prop for shock absorbtion if you hit something. When the rubber ages and starts slipping, it does exactly what you described. Sometimes you can’t see that the rubber is even there. To check for this, take a permanent marker and make a mark from the prop to the hub. Then run it until it revs, and see if the marks are still aligned. There are places that can repair this problem, but on small HP motors like yours, it’s usually cheaper to buy a new prop at a discount place like propcopropellers.com.
Dave

[20mercman]

I agree, I suspect that you have a slipping hub. Good advice by outbdnut2. I had that happen last year on my FD-10 (1956 15hp Johnson)

Steve

[chris-p]

If the prop is in good shape, have it re hubbed. If it is dinged badly, get a new prop.

[frankr]

picture host

[paawe123]

Thanks so much for your answers and help. I will check to see if it is slipping.

[amuller]

Yes, slipping hub. It is possible, if you are in a fix and really need to use that prop, to drill a transverse hole and pin the prop to the hub with a roll pin or suchlike.

[rjoynt]

An easy way to check if it is slipping is to use a marker and draw a line through the mating parts. If it is slipping, it will show that it moved. Never had to try it, knock on wood, but it makes sense.

[Author]

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