Re: [Amel Yacht Owners] Engine blower fan


All that Bill R says, and a little bit more... 

In short, the Amel forced ventilation fans are an important part of the system, and should be replaced if they fail.  A failed fan is not an urgent emergency, but it absolutely should not be ignored either.

The engine block itself doesn't really care about the ambient temperature, and loses a negligible amount of heat to the surrounding air even if it was very cold.  But... 

A diesel engine not only requires air to breath, it also requires COOL air to breath.  Engines do not like inhaling very hot air, it reduces performance significantly because the amount of oxygen available per cubic foot is reduced.  As a VERY rough estimate, increase the temperature 3 deg C reduces the O2 content per cubic foot by 1%.  Raise the supply air temperature by 30C, and the power the engine can generate drops by 10%. That's not peanuts. The cooler the intake air the more power the engine will generate, and the more efficiently it will burn its fuel.

One published formula for the MINIMUM air flow into a diesel engine room is 
(2.75 * HP) - 90 = Cubic Feet per Minute.  

For the Volvo TMD22 this would be about (2.75*75)-90=116 cu ft/min.  And that is a bare minimum. There is no such thing as "too much." 

In some cases, you can supply this much air with passive ventilation, certainly many boats do (or try to!) but Amel's vents are too small for this.  

Keeping an engine room as cool as possible has LOTS of advantages far beyond the comfort of the humans who might have to enter.  All electrical equipment, including the alternator, work better and last a LOT longer if cool than if hot.  On a Super Maramu, keeping the genset supplied with cooler air is important to have it last, because the generator windings are air cooled. Not to mention: battery chargers, transformers, inverters, assorted electric motors, and what-all-have-you. All are air-cooled and would be very unhappy in an unventilated engine room that could easily top 60 deg C after a long motor in the tropics.

Bill Kinney
SM160, Harmonie
Spanish Wells, Bahamas

---In amelyachtowners@..., <brouse@...> wrote :

I suspect that the engine's heat exchanger does 99% of the job in cooling the engine and the blower/fan does the rest of the job for the engine. I suspect the blower/fan's primary mission is to ventilate petroleum fumes and make the engine room a better place for you.


CW Bill Rouse
Admiral, Texas Navy
Commander Emeritus

Amel School
720 Winnie St
Galveston Island, TX 77550

+1(832) 380-4970

On Tue, Jan 15, 2019 at 10:40 AM smiles bernard smilesbernard@... [amelyachtowners] <amelyachtowners@...> wrote:

Hello there
I was wondering about the fragility of an engine cooling system that relies on an electric blower /fan
This I presume is the case for all Vintage Maramus - not sure if it’s also the case for Super Maramus too?
In the older Maramus like mine the blower fan is located in the port cockpit seat coaming area
I wondered if in the case of the electric fan failure it would be ok to simply remove the fan altogether and let the engine draw/suck air through he delivery ducts that the blower uses.
Any thoughts on this one?
Is the blower fan actually necessary in case of failure ?

Thoughts and any experience much appreciated

All the very best

Maramu 46 #162

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