Engine blower for Yanmar 4JH4E

[JohnB40]

Hi
I have a small blower that blows air into engine compartment through a 4 inch plastic ducting. There are two similar ducts that would lead air from engine compartment back out other side of the stern.
This blower has broken. It is VERY difficult to get at. Do I need it?
Someone suggested engine might overheat but think that is not happening. Or is it just to ventilate any fumes out of the compartment?
The boat is 2009 Beneteau 40.
Thanks for help, JohnB40

[noelex 77]

Welcome to the forum John.

Diesels use a lot of air.

The engine compartment can get hot. Rather than overheating the engine (the water cooling usually has plenty of reserve capacity) the hot intake air makes the engine less efficient and it produces less power particularly if it struggling for air. The ancillary components like the alternator will run hotter which is not great for their life expectancy.

Long term you should replace the fan, short term its fine to run without it.

An old crude trick to see if the engine is struggling for air is to crack open the access hatch. (When the engine is working hard) If the engine speeds up it was not getting sufficient air. You can also measure the temperature in the engine room. These tests will give you some idea of how essential the fan is in your particular installation.

Unfortunately boat builders have a habit of placing equipment where it is very difficult to service. With a bit of patience and a lot of swearing there is usually a way. Can the fan be mounted somewhere else?

Check the fan is getting power with a multimeter before you replace it. It is not unusual for the problem to be a bad electrical connection somewhere in the circuit rather than the fan itself.

There are some tricks such as bluetack on the heads of the screws so they stick to the screwdriver and taking pictures with a small digital camera to see what is going on in areas that you cannot get too, or to find a dropped screw. Good luck !

[JohnB40]

noelex 77
Thankyou for a wonderfully clear and comprehensive reply. The best to you, JohnB40

[dansken]

I would think that the blower is extracting air rather than blowing air into the boat....

[DeepFrz]

The blower should be extracting hot air rather than blowing in to the engine compartment. The reason for two ducts on the other side is so cooling as well as combustion air can get into the engine compartment.

Check the temp. of your alternator when it has been working hard on a hot day. You may want to install a fan to blow air directly onto the back of the alternator.

A hot engine compartment usually affects more than just the engine. There is often quite a few other components installed in there.