Engine bay fan?

[TimBennet]

Any recomendations or a suitable fan to install for a 35 bhp engine?

AS usual, ASAP Supplies have a good range. But you would have to head their caveat:

"Please note: All marine engines are able to draw sufficient air to operate efficiently, provided that the vent openings are adequate. The purpose of these extraction blowers is to remove air / fumes from the engine room once the engine is stopped. Extraction ventilators should never be operated when the engine(s) are running. The suction power of the engine(s) may over-rotate the ventilator and cause the electric motor to burn out."

 

[Birdseye]

I need to pump cold air at the alternator which is burning out regulators too often. If it then gets munched up by the engine, so be it. The asap comments reflect on the quality of the items concerned - the computer fan I currently use has had no problems. But then chinese tat made for HP in volume might well be better made than low volume chinese tat made for boats.

 

[Lakesailor]

Thread: Engine bay fan?

I like them, but wouldn't call myself a fan.

 

[West Coast]

I need to pump cold air at the alternator which is burning out regulators too often. If it then gets munched up by the engine, so be it. The asap comments reflect on the quality of the items concerned - the computer fan I currently use has had no problems. But then chinese tat made for HP in volume might well be better made than low volume chinese tat made for boats.

Your problem is going to be to find a way to duct cold fresh air into the starlight engine compartment, especially to the specific location of the alternator.
I appreciate you have a problem with regulators giving up, but I am not aware of any other starlights with the same problem so am not convinced it is simple overheat. Am wondering if your regulator problem is not caused by something else in your electrical system?

 

[aquaplane]

. The purpose of these extraction blowers is to remove air / fumes from the engine room once the engine is stopped. Extraction ventilators should never be operated when the engine(s) are running. The suction power of the engine(s) may over-rotate the ventilator and cause the electric motor to burn out."

An extraction fan will be working against the inflow of air pulled in by the running engine so it should be slowed down if anything. The ASAP statement doen't make sense to me. If it was a blow fan I could see their arguement but I wouldn't fit one as I believe that the way to go is to extract the hot air and fumes.

 

[30boat]

I think ASAP very untipically got this one wrong!

 

[Birdseye]

Your problem is going to be to find a way to duct cold fresh air into the starlight engine compartment, especially to the specific location of the alternator.
I appreciate you have a problem with regulators giving up, but I am not aware of any other starlights with the same problem so am not convinced it is simple overheat. Am wondering if your regulator problem is not caused by something else in your electrical system?

I wonder too. But what else could it be?

I intend to mount the fan in the lazarette and pipe the air underneath the rear cabin lockers into the stbd side of the engine box and then over the top of the engine to the alternator,. This will be a push system. There is a good vertical vent up the side of the companionway

 

[NickTrevethan]

We have a blower. Makes a lot of noise and helps shift stale boat smell from engine bay before opening the hatches.

I run it before starting as a precaution against gas risk, and afterwards to waft some cooler air into the space afterwards. On or off seems to make zero difference to to running of the engines.

 

[prof pat pending]

I wonder too. But what else could it be?

I intend to mount the fan in the lazarette and pipe the air underneath the rear cabin lockers into the stbd side of the engine box and then over the top of the engine to the alternator,

I'm not familiar with your boat, but do you need a fan at all?
Pipe your engine bay fresh air to a location by the alternator and use the draw of the engine to pull the air over the alternator.
If you wanted to go a step further perhaps you could position your engine intake close to the alternator with something like an automotive style induction kit.

 

[West Coast]

I wonder too. But what else could it be?

I intend to mount the fan in the lazarette and pipe the air underneath the rear cabin lockers into the stbd side of the engine box and then over the top of the engine to the alternator,. This will be a push system. There is a good vertical vent up the side of the companionway

How about a remote regulator, mounted outwith the engine compartment?

 

[affinite]

Apparently some Moody engine bay ventilation fans were suckers and some were blowers so even a respected builder couldn't decide. My blower appears to have packed up years ago but concern over high engine room temps prompted me to replace it this year. The ducting on my boat suggests that it was a blower but Im going to fit a "snorkel" in the engine bay and configure the fan as an extractor because my main priority is removing hot air/gasses from the engine bay and rear cabin after running.
Currently wired to run on ignition switch on but I intend to fit a 30 min overrun timer instead. Incidentally I cant see how to make up a suitable relay circuit to do that ie fan on for 30 mins AFTER ignition switched off so any suggestions gratefully received

 

[West Coast]

Apparently some Moody engine bay ventilation fans were suckers and some were blowers so even a respected builder couldn't decide. My blower appears to have packed up years ago but concern over high engine room temps prompted me to replace it this year. The ducting on my boat suggests that it was a blower but Im going to fit a "snorkel" in the engine bay and configure the fan as an extractor because my main priority is removing hot air/gasses from the engine bay and rear cabin after running.
Currently wired to run on ignition switch on but I intend to fit a 30 min overrun timer instead. Incidentally I cant see how to make up a suitable relay circuit to do that ie fan on for 30 mins AFTER ignition switched off so any suggestions gratefully received

I bought a module from ebay - search for "12v time delay relay" - loads of devices for £5 to £15 with adjustable timer, just choose the mode of operation you want.

 

[abraxus]

AS usual, ASAP Supplies have a good range. But you would have to head their caveat:

"Please note: All marine engines are able to draw sufficient air to operate efficiently, provided that the vent openings are adequate. The purpose of these extraction blowers is to remove air / fumes from the engine room once the engine is stopped. Extraction ventilators should never be operated when the engine(s) are running. The suction power of the engine(s) may over-rotate the ventilator and cause the electric motor to burn out."

And yet they sell ones that are specifically described as "continuous duty" blowers.

I run mine all the time because I'm river based so hardly get much beyond idle speed. I guess the ideal set up would be to not only have a timer to switch off at a set time after engine shut down, but also an automatic switch that turns it off over say 1500 rpm's and on again if/when the engine drops below that.

 

[Birdseye]

How about a remote regulator, mounted outwith the engine compartment?

In effect I have that with a Sterling regulator but for some reason it wont regulate on its own. I did try to talk to Sterling about it but the phone was answered by an irishman with the ryanair attitude to helping customers

 

[Birdseye]

How about a remote regulator, mounted outwith the engine compartment?

In effect I have that with a Sterling regulator but for some reason it wont regulate on its own. I did try to talk to Sterling about it but the phone was answered by an irishman with the ryanair attitude to helping customers

 

[West Coast]

In effect I have that with a Sterling regulator but for some reason it wont regulate on its own. I did try to talk to Sterling about it but the phone was answered by an irishman with the ryanair attitude to helping customers

Complete thread drift now (apologies to OP) but when did you fit the sterling regulator? Were you having problems before this? While my engine is not the same as yours, the alternator is and I have never experienced this problem. Your engine and mine has very similar output, probably running at similar temps in the same size of box with the same air intake etc. I have never experienced an alternator problem when I bought the boat, or after I fitted a regulator (Merlin type) back a few years ago. Other starlight owners I know have not had issues. I am thinking that overheat is a red herring!

 

[Birdseye]

replied by email

 

[Birdseye]

Apologies for bringing this old thread back to life but I've just been looking at the Shurflo fan above. It rates at 3.4 cu m/min. Now I reckon my volvo 2030 engine at its normal 2500rpm sucks in a 1 litre lungful of air at 1250 times per minute and there are 10^-6 litres in a cu m so call it 1.25 cu min demand. Does this maths look right to you - I am good at sloppy order of magnitude errors.

My problem is that the engine box has whats best described as a snorkel vent of maybe 10 sq inches cross section rising vertically . Its difficult to see any real cooling flow out of this vent with the engine sucking air in. So my thought was to use this fan to pump air from the lazarette into the engine bay allowing any surplus already heated air to go up the snorkel. Makes sense?

Two issues. ASAP saying the fan is designed to extract not push for fear oif the fan speed going into orbit. Second is the risk of hot engine fumes into the cabin. But doing things the other way round requires the fan to suck air down against a natural warm air flow upwards

 

[Spirit of Glenans]

What's a "special" extraction fan?

QUOTE]

A sparkless one, suitable for venting combustible gases.

 

[jon711]

And yet they sell ones that are specifically described as "continuous duty" blowers.

I run mine all the time because I'm river based so hardly get much beyond idle speed. I guess the ideal set up would be to not only have a timer to switch off at a set time after engine shut down, but also an automatic switch that turns it off over say 1500 rpm's and on again if/when the engine drops below that.

They, as are most of the EXTRACTOR units continuosly rated but not designed for continous operation. The typical motor life on extracor fans for engine compartments have a motor life ranging from 300 to 1500 hrs!! So they will run continuosly for that period with out issue. So continously rated, but not designed for continuos operation.

The large boatbuilders mentioned earlier in the thread were advised on this when the boats were specced out, but chose to ignore this advice.

The engine will pull enough air in with out a fan, indeed a moving fan in the ducting will REDUCE air flow as in effect it is creating a disc in the pipe work (Remember the thread about free wheeling or locked props - same principle).

How do I know all this? I was involved with testing all the extractor style fans, when I worked for one of the manufacturers, and we tested ours and our competitors to destruction.

THIS DOES NOT APPLY TO FORCE AIR FED ENGINES which use different blowers.

Tim B is very correct, as always...

Jon