What exactly does this knob control?

[jv20]

Any help? Would this control be engine room temp, or is it an oil heater in the motor? This picture is taken off my panel box

[Sailmonkey]

From the looks of it.........well there's nothing to look at.

[TomM]

That's your stealth mode control knob and right now its set to max.

[jv20]

Sorry I thought I downloaded a pic lets try again, and its on my 42 ocean

[atoll]

engine room fan or blower control?

[Sailmonkey]

I'd venture to guess it's to turn on/off the engine room blowers based on the temperature of the space. Adjustable so that a boat from Maine would be able to adjust the max temperature for say Louisiana to prevent the fan running continuously.

This is installed so that after engine shutdown the fans will stay on until the excess heat is evacuated to the set point.

[S/V Illusion]

Why guess or have us guess? The best thing any boat owner can do is to thoroughly investigate his boat's equipment including the wiring. The most obvious benefit would be in KNOWING where everything is before as problem or emergency arises which is not a good time to start learning.

[jv20]

Thanks I agree, we have spent the summer learning all the systems and I find new things every time I'm there. Didn't get a lot of detailed systems info when we bought her and never noticed this control before. I called and had a dealer tell me he thought it was a block heater control. I guess we will see.

[Therapy]

I would say Sailmonkey is right but without any kind of scale with the knob I wonder what real good it could be unless used as just on/off.

[Sailmonkey]

Originally Posted by jv20

I called and had a dealer tell me he thought it was a block heater control. I guess we will see.

I would be amazed if they put an external thermostat control on the block heaters. I can't think of a good reason to have a variable temperature for something that is simply to prevent cold starts.

[David M]

It is better to trace the wires rather than guessing.

[Sir Rondo Normal]

Haha, I recently went through the same thing... I rewired my eng rm fans direct to the batt switch so that as soon as I turn the switch on to start the engine, it comes on and does not shut off until I turn the batt switch off. That way, I can't start the engine without the fan being on first and I can't forget to turn the batt switch off because I can hear the fan going.

[David M]

Originally Posted by Capt Wraun

Haha, I recently went through the same thing... I rewired my eng rm fans direct to the batt switch so that as soon as I turn the switch on to start the engine, it comes on and does not shut off until I turn the batt switch off. That way, I can't start the engine without the fan being on first and I can't forget to turn the batt switch off because I can hear the fan going.

Add a switch but leave it on if you think you might forget. There will be times you want your electrical system on but your fans off, such as when you are working on your boat at the dock but don't need your engine running. You also want a fuse to protect the wiring. Without a fuse you have a source of ignition if your wire melts, which is the very purpose you have an engine space ventilation fan.

[Sir Rondo Normal]

Originally Posted by David M

You also want a fuse...

Yes we must always have a fuse. Sorry, shouldn't have made it sound like I omitted the fuse. I have't had the need for a secondary switch but it would probably be a good idea to have one, like you said and then just leave it on.
The original switch on my boat was broken so I essentially just bypassed it.