Over-heat switch Johnson 40

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Over-heat switch Johnson 40

Post by LitchboroughLitchbor »

Hello All

In the distant past, the over-heat warning light on my 1962 Johnson 40 RDS-24 had a tendency to come on, causing great alarm. After throttling back, it normally went off.

For this season's service, I've decided to investigate further and have got the part out of the cylinder head. Unsurprising one of the terminal posts has come adrift, but nonetheless, it is showing no continuity in a boiling saucepan - so I think it's time for a new part.

New parts seem to be extremely scarce and horrendously expensive - about $150.

The working part is a bi-metallic thermostat switch (NO - normally open) that closes at 211°F (99°C).

I've found a generic part, closing at 90°C, stocked by Switch Electronics in Hull, for £1 each. (They also offer 95°C and 100°C components, but not from stock). This will need a little modification and soldering to the existing wiring.

Does anyone have any experience of this? Will it work?

I've wondered what a sensible person would do. Leave it disconnected, and wait until the pistons melt? Buy a modern engine?

Well, I know I'm not a sensible person .....
Screenshot 2021-05-13 at 20.21.14.png

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