Need to reconnect my fan in my engine room. When is it supposed to work?

[zeseb]

I have a Yanmar 4JH4 75HP engine in my boat.
I bought this boat 1 year ago and there is a brand new fan in the engine room at the opposite side of the air entry of the engine. This fan has also a flexible duct pipe as his rear.

So I am pretty sure this is to evacuate the heat of the engine when running.

The fan had never run and I discovered today why... The electrical wires are not connected to any source. So I think it was an ongoing project of the previous owner who just gave up.

My question is; is this fan supposed to work whenever the engine is running or only when the engine temp is reaching a certain point? I ask that for saving batteries and then wire it properly.

[GILow]

I wired mine to be switched manually. I turn it on before starting the engine and turn it off when the engine has cooled down, about two hours AFTER I shut the engine down.

I certainly would not run an engine without a blower, aside from heat buildup, you are likely to get fumes from the engine in the boat without the fan running.

[transmitterdan]

I assume you have a Diesel engine. The answer is different if you have petrol/gasoline engine.

The fan should push air out of the boat. The inlet to the fan should be relatively high in the engine compartment. There must be a source of fresh air to replace the exhaust air. The fan only needs to run when engine is running. Optionally, the fan could run for a while after engine shutdown to remove excess heat.

Also, it is mandatory that any electric fan exhausting the engine space must be fitted with an automatic shut down in the event of fire detection. If a fire breaks out in the engine space that fan will feed the fire the oxygen it needs. It’s also a good idea to automatically kill the engine when fire is detected. Xintex make shutdown systems like this.

Under no circumstance should you arrange the fan so that it blows air into the engine room. It should only be used to exhaust air. If the fan blows air into the engine space then exhaust gases might be forced into the living space which can be hazardous.