Newbie. How to supply more air to my engine compartment.

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michaela

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I bought an old sailing boat with an old volvo md6b (10 hp) engine, which I've grown attached to, having done about 90 hours of motoring with it when travelling around Holland with the boat, and bringing it back to the UK this year.
The engine cabinet is very close fitting and I have measured the air temperature after running the engine for short time intervals and it is very hot. I have fitted an rpm guage and don't run the engine at greater than 80 percent of its max rpm . Because of the close fitting nature of the cabinet I'm convinced that the engine air supply needs to be improved. I could do this by fitting louvres but if I ship a load of water I don't want the engine to be under water. Also by making holes in the front of the cabinet I'm going to be screwing up the sound insulation.
The engine sits under the cockpit sole and is isolated from the side lockers. The boat is a Varne 850.
What are my options? Preferably low cost as there are multiple other boat things I need to spend my money on (under the wifes radar).
 
For what it's worth my Bene has 2 4" pipes coming from the sugar scoop area with a fan that is on continuously sucking hot air out from the top and allowing cool air back in. When it stopped working it the temp of the compt shot up. So my advice. Get some air hose, tumble dryer stuff is ok and plumb a fan in
 
Onia said:
Would you be able to fit a 12v 'engine blower' fan to push air into the engine compartment from the saloon?
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Aren't they usually set to suck Andrew (although they are usually referred to as "blowers") ?

It would seem better to have a duct from the engine compartment to outside and suck the air out, it will draw it in somewhere as a rule, if not a closable vent into the saloon or somewhere suitable should do the trick.
 
I second Onia's suggestion of a 12v engine blower fan. Perhaps it could be rigged to come on as soon as the engine is started?
I would be interested to know what temperatures you were getting in the engine bay though? And if it comes to that, what temperature is actually too hot!
 
The engine blower is a good idea but it should be installed to extract from the engine compartment not blow air in. By extracting you remove the heat from the engine space. The extracted air will be replaced by cool air from the boat or anywhere where an opening exists. The other advantage of extract is that it will remove fumes from the engine if you have a diesel leak or leaky exhaust. We run a large centrifugal fan that extracts to a Perko cowl on the coaming. It drop the engine room temperature by 20 degC.
 
Thanks for the suggestions guys. I could certainly attach some type of blower from the saloon. I like the idea of a system where air is sucked in and pumped out overboard at the same time, not quite sure how one would stop water entering through these pipes though? I measure engine temperature using a hand held IR device (£10) off ebay. I normally point at the engine block which is between 60 and 80 C. I would need to point it into the bay but not at the engine to get an idea of the air temp around the engine.
when I first got the boat it over heated badly while waiting permission to enter one of the locks leaving Antwerp marina en route to the Schelde. When I took the heat exchanger off it was totally coked up which I cleared as well as I could.
 
This is a water cooled engine. If it is overheating there is a problem with the cooling water system. Blowing air on it isn't going to solve the underlying problem.
 
Engine overheating solved, I believe, but engine bay still gets hot and any clothes worn on the boat have a dieselly smell to them. I've read somewhere that the engine bay shouldn't be higher than than 140 otherwise the alternator is effected. Glad of the heat in the winter but want to make sure I'm not damaging the engine in the summer. Will try and get some temp figures for the engine bay after a good run.
 
parsifal said:
This is a water cooled engine. If it is overheating there is a problem with the cooling water system. Blowing air on it isn't going to solve the underlying problem.
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Do keep up at the back, he said he fixed the overheating of the engine! The Beneteau system, which I described, by the way pumps hot air out of the engine compartment to the sugar scoop area and allows cool air from the other side in to replace it!
Stu
 
A quick trip to the London boat show might be an opportunity to see how various new yachts fit these fans in yacht engine bays . Ours turns on when ignition is switched on and stays on after shutting down . Alternatively if not going to LBS just look at a few engine bays photos of any of newer Moody's which have them. I suspect no doubt also found on Hanse and Dehler nowadays as well as the Bens mentioned
 
The engine itself will draw in far more cool air than any fan. The clever trick is to direct this cool air over the engine, before it goes into the air intake.

It is good practice to have a flame proof extraction fan for battery compartments. If charging from shore power, it makes sense to run the fan for some minutes prior to starting the engine, to get rid of any accumulation of hydrogen. But running an extraction fan to suck air out of the engine space, while the engine is sucking it in, is pointless.
 
I run an MD7A in my 24 footer and find even pushing hard it is a very cool running engine, and would expect the 6 to be similar. If the engine compartment is so well sealed as to get over hot, does the engine get enough air to breathe? Even small donkey like these need a lot of air to run, and I would think in a small engine box it should be using enough air to change it. It's not helpful to supply hotcake to a diesel. Many bigger turbo engines have intercoolers to keep the inlet air temp down, so allowing more oxygen to the engine.
 
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oldharry said:
I run an MD7A in my 24 footer and find even pushing hard it is a very cool running engine, and would expect the 6 to be similar. If the engine compartment is so well sealed as to get overnight, does the engine get enough air to breathe? Even small donkey like these need a lot of air to run, and I would think in a small engine box it should be using enough air to change it. It's not helpful to supply hotcake to a diesel. Many bigger turbo engines have intercoolers o keep the inlet air temp down, so allowing more oxygen to the engine.
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Ah! The joys of predictive text.
 
But running an extraction fan to suck air out of the engine space, while the engine is sucking it in, is pointless.[/QUOTE]

What is your technical arguement for this comment? Are you a qualified ventilation expert? Do you design these systems for a living? Please clarify this remark so we all understand the basis
 
NormanS said:
But running an extraction fan to suck air out of the engine space, while the engine is sucking it in, is pointless.
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Both my engines have extraction fans which suck air out of the engine space all the time the engine is running. All the Leopard cats are build like that, although I've now fitted remote switches to both fans so I can turn them off when the engine is not working very hard.

Richard
 
skipper_stu said:
Do keep up at the back, he said he fixed the overheating of the engine! The Beneteau system, which I described, by the way pumps hot air out of the engine compartment to the sugar scoop area and allows cool air from the other side in to replace it!
Stu
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We're discussing a 28' yacht with a little 10hp engine. (Which is what I have, incidentally) and you're saying it needs cooling fans? Don't be ridiculous.
 
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