Engine room ventilation

[lumphammer]

The engine bay on my Moody 36 has two air vents one that provides air at the top and the other at the bottom. Neither has a fan attached.
I would like to use the top one to remove hot air with an extractor fan, but I'm wondering if extracting air affect the performance of the engine.

Am I being overly concerned? Is it a good idea?

 

[Ex-SolentBoy]

The engine bay on my Moody 36 has two air vents one that provides air at the top and the other at the bottom. Neither has a fan attached.
I would like to use the top one to remove hot air with an extractor fan, but I'm wondering if extracting air affect the performance of the engine.

Am I being overly concerned? Is it a good idea?

It is a good idea as long as the air coming in is sufficient.

We have this fitted.

It comes on as soon as the boat is powered and one of its functions is to remove gas from the bilge area before starting the engine. Its connected to a thermostat for engine cooling.

 

[david_bagshaw]

better to blow cold in at the bottom,as an additional entry to the e room then there wont be a lower air pressure in the engineroom, by sucking out.

 

[oldsaltoz]

Have you calculated the volume of air your engine uses?

Extractor are normally used to remove hot air and engine room smells just after engine shut down only.

Some petrol engines have them to blow out petrol fumes BEFORE starting.

Think of it this way, a 2 litre 4 stroke engine at just 400 RPM will draw in 100 litres of air every minute, at 3000 rpm it will use 400 litres of air every minute, so why would you need a fan running?

Good luck and fair winds.