Dumb Question - Sorry

[mark.adams]

We have a blower fan fitted in the engine compartment that vents outside, should that be on all the while the engine is running?

 

[Alpha22]

Petrol or diesel?

Does it blow or suck?

 

[mark.adams]

Petrol Volvo Penta AQ130 and it sucks from within the engine compartment and blows outside.
Only asking as i saw whisps of fumes at the vent outside, so put it on and it cleared, but was never told whether it should be on or not whilst engine is running

 

[KINGFISHER 9]

Should be running for 4 minutes before you start the engine then also while you're pottering, switch it off when you get up on the plane .... so says my Mercruiser handbook anyway! Probably the same for Volvos.

 

[Prhperio]

Petrol Volvo Penta AQ130 and it sucks from within the engine compartment and blows outside.
Only asking as i saw whisps of fumes at the vent outside, so put it on and it cleared, but was never told whether it should be on or not whilst engine is running

I think the idea is to ensure that the engine room is free of any petrol or other vapours before you ignite the engines, so run it for a while before you start up IMHO.

 

[Spi D]

No harm in running it also on plane.

If you observe anything coming out of the engine room (besides a little heat), you need to investigate for leaks. The fan's primary task is to suck out fuel- and other explosive fumes, like gas from a cooker/stowe (heavier than air, will find it's way to lowest point in boat).

As opposed to diesel petrol is highly flammable, hence the question about engine type.

 

[mark.adams]

aah, looking at the photos i took (in the engine cooling question) the corrugated pipe at the stern is what connects to the fan, i reckon the small pipe that feeds into it is the crankcase breather therefore the fumes i saw would be from the crankcase, i think it would be wise to leave the blower on all the while the engine is running

 

[Spi D]

Sounds reasonable. Routing the crankcase vent into the sucktion hose isn't common, but presumably harmless.

 

[abraxus]

I believe the usual thing is to run it for several minutes before starting and then turn off once up an running. Nothing wrong with running it all the time though, but you may want to check if it's rated for continuous duty as not all are.

That said, mines at least 12 years old (possibly twice that) and I doubt it's rated for continuous use, but I leave it on and it hasn't broken yet.

 

[sprocker]

I was told to run mine for 4 - 5 mins before starting, and for at least 10 mins after fueling (Petrol). I tend to leave it running until I'm out of the harbur then turn it off when I get out
of the 5 knot zone and speed up a bit.

 

[Chris_d]

I have always understood these are to clear fumes before starting and refueling, the description blower has always seemed wrong as they do indeed suck!
There would be no point running it when crusiing as it will simply be competing with the engine to suck air out of the engine compartment, so why leave it running
and to just wear it out.
Some much larger vessels do indeed have "blowers" that feed the engine with fresh air, but this is unusual on a leisure boat.

 

[boatingdave]

The gist of all these comments are correct. The vent fan is designed to extract any potentially explosive vapours from the engine compartment prior to starting her up. Given the air being sucked in once the engines are running it is no longer needed, once running at speed the airflow being sucked in is quite significant. I had a petrol boat for a number of years. The only thing I'm not sure about is you say the crank case breather is being fed in, that is very unusual as this is usually fed back in for combustion?

 

[boatingdave]

Btw. Not a dumb question, if you weren't told how to operate the engines properly much better to seek guidance, you will always get plenty of advice on this forum, lots of experience from folk who have been boating a long time.

 

[Mymobo]

Run for 4 mins before starting and stopping and when running at low revs.

 

[boatingdave]

Run for 4 mins before starting and stopping and when running at low revs.

Ronan, evening sir. I often forgot to run mine when stopping, good point, especially with carbs as the heat from the engine used to evaporate any fuel still left in the Holley carbs.