Engine room ventilation and air intake question.

[ianainge]

Myself and my 2 neighbours all have Volvo 63p`s, one a 2005 Phantom 40, one a 1998 Princess 430 and mine a 1998 Princess 360. The 40 has 2 engineroom cooling fans and 2 extractors, the 430 2 fans and the 360 2 extractors, does anyone know why some have fans and one has extractors only.

Secondly the 360 has air intake hoses from the side vents on the boat directly into the air intake box where the other two have no hoses and rely on the air in the engine room to be drawn through the filter.Does anyone else have these hoses.

I hasten to add the one with the hoses has a cleaner transom after a long journey.

 

[Miss_DANKA]

My P360 has 1x extractor and 1 x blower, they look identical but one is cross wired, they are sited just under the patio doors and central.

Have you checked yours to see if one is extracting in reverse hence blower ?

Yes my 360 also has pipes to feed fresh air direct to the air filters, this should give cooler air to the intakes, otherwise the air would be warm air from the engine bay (the cooler the better).

One thing that puzzles me is my blower and extractor are sited at the side of each other so I do not expect much air is circulated as you would expect the two to almost cancel each other out ?

Do your fans run all the time the engine is on or just for 10 mins ?

In my opinion two blowers are best to force clean air in, any combustible mix will be forced out through the vent holes ?

 

[ianainge]

My fans are sited in the forward area of engine room one in front of each engine, i will check the wiring on them.

my fans run on start up and on stopping there is a timer of about 4 mins, the service manual says this should be adjusted to 10 mins in the summer ,timer switch is located in fuse board in aft cabin.

 

[andy_wilson]

I view fans as a great way to vent the engine space before starting, and even to vent it after stopping in hot weather to prevent the boat getting too hot.

Clean, fresh, cool air at the air intake is always best for complete combustion, and can be designed for quieter running too. Best to have ample intakes and ducting leading to the air filters. Another to the alternator(s) is also a good idea.

Alternatively sucking air from below floors (against the hull) will be cool.

I often wonder about fan capacity. Engines potentially consume HUGE amounts of air, more than any fan I've seen on a boat can supply.

Take 5 lit. swept volume at 2,000 rpm.

2,000 (rpm) X 0.5 (4 stroke sucks air every other cycle) X 5 (litres swept volume) = 5,000 litres / minute.

Anything that aids supplying this is going to help avoid soot particles on the transom.

 

[Stoaty]

[ QUOTE ]
I often wonder about fan capacity. Engines potentially consume HUGE amounts of air, more than any fan I've seen on a boat can supply.

[/ QUOTE ]

Just a bit of trivia. I had a one man hovercraft many years ago and the fan on that shifted 440 Cu ft of air per second!

 

[Powersalt]

never really thought about this. I have 63p,s on my prestige 36 but no blower or intake fan?? should I have one?
The electrician has commented that the intakes are close to the electrics and should be shielded. But what about a blower and if I fit one what how and where??

 

[markdj]

For petrol engines an extractor is required at the bottom of the bilge to run for 30 seconds before starting the engine and then turned off.

Battery boxes should have either an active or passive vented supply of air to stop the build up of hydrogen gas due to charging.

For petrol and diesel engines, they both require blowers to supply fresh air to the enigne and all extractors should be turned off. The egine consumes the fresh air and chucks it out the exhaust.

There are many continuously rated fans, (Jabsco do them), that supply enough air to adequately supply 600hp engines.

 

[Nauti Fox]

A couple of points on my elderly installation.
When I first got the boat there was always an engine smell in the saloon when running. On investigation the intakes were in the lazzerette and it had an engine driven blower and extractor and was extremely hot in the engine room. I disconnected the engine driven fans and fitted in-line electric extractors in their place, also removed the inlets from the lazzerette and fitted mesh over the turbos allowing them to suck air from the engine room. With the extractor fans off it allows sufficient air through them to keep the engine happy and with the intakes inside the engine room there is a constant flow of air to keep that much cooler.