Fellow Beneteau 331 owners - Engine Compartment Ventilation

[Still Grinning]

Hi all again - looking for advice from the East Coast B331 collective.

I know that in the States, the US version of this boat has a fan on the large duct from the engine compartment exiting at the stern.

Mine does not - should it? Does yours?

Thanks in advance!
Rgds
Still Grinning

 

[Brooksie89]

Is heat build up a problem in your engine bay?

Mine definitely is. I've got a beta 20 engine, twice the power output of what was probably originally installed. The belt is throwing lots of black dust, suggesting it's too hot. The engine compartment is about twice the size of the engine, with nowhere for heat to go.

I'm fitting a blower to pull hot air out. If needed I'll fit a vent, but replacement air can come from the bilges in the short term.

 

[PeterWright]

Hi,

When thinking about engine space cooling, you need to remember that the engine itself is sucking in half its swept volume every revolution so at 1500rpm a 1 litre engine is sucking in 750 litres/minute. The air is drawn mostly from the bilge with the bilge being recharged from air vents or the open companionway via the accommodation. The prime heat rejection from the engine is via the water cooling system which sends 2 to 3 times the power being delivered by the engine down the exhaust pipe. A key feature of the water cooling system is that it is controlled not to cool the engine itself below ~90 C, so the air immediately adjacent to the block will heat to around this temperature however much extra air you blow through the engine space. The flow rate you can pass down a 2 or 3 inch hose is unlikely to make much difference. There s an endless debate about suck or blow; if you blow into the engine space, the air supplied will simply be swallowed by the engine, so less air will be drawn from the bilge and no additional flow to aid cooling. However, if you suck air out from the engine space, you will increase the flow rate from the bilge, so you will provide a bit more cooling.

In the good old days of petrol engines, engine space extract fans were an essential precaution to remove petrol vapour from the hot engine space especially before energising the starter motor with its risk of brushgear sparking and after shutdown, when the engine consumption airflow and cooling water flow stop, but some parts (exhaust manifold) are still pretty hot. Nowadays, the one engine room component in need of temperature protection is the alternator, which heats itself above the ambient temperature and contains diodes which are prone to failure at elevated temperatures.

 

[davidej]

I have a Bene 361 which is the almost identical bigger brother. It definitely has a fan but I have never checked whether it sucks or blows. There is a duct from the transom fan to the alternator _-I suppose the one part that could get hot and would not be cooled by the water coolant system.

 

[MaxM]

I don't have my 331 (2002 vintage) any more but I recall there was a duct from the transom which ended close to the engine air filter (foam cylinder). There wasn't a fan (not on the wiring diagram) although there did seem to be one on larger models - 361, 381. I only had a problem with overheating once (in the middle of the North Sea, of course!) but I put that down to a) prolonged high speed, b) new 3 blade Brunton Autoprop (great bit of kit), c) some gel like sediment round the fresh water side of the heat exchanger (discovered during the winter service).
It was recommended to me that, if you are running for long periods, that you should run off domestic hot water periodically to help with the cooling - it certainly gets hot. On the occasion it overheated, it also tripped the reset on the electric immersion heater - took a bit of diagnosis and finding the button.

 

[jimi]

I had a 331 with a yanmar 3gm no fan, no issues.

 

[Hydrozoan]

Is heat build up a problem in your engine bay?

Mine definitely is. I've got a beta 20 engine, twice the power output of what was probably originally installed. The belt is throwing lots of black dust, suggesting it's too hot. The engine compartment is about twice the size of the engine, with nowhere for heat to go.

I'm fitting a blower to pull hot air out. If needed I'll fit a vent, but replacement air can come from the bilges in the short term.

I have a similar Beta and was concerned about dust shedding. Temperature test strips kindly supplied by Beta showed no problem, and the pulley bearing surfaces were free of any corrosion. Two things did the trick: (i) a cogged or notched belt and (ii) as a secondary issue, observing that at a particular and narrow engine rpm band the belt vibrated a little more than usual and was just catching the screw of a Jubilee clip on one of the engine hoses!

Forgive me if you have already been through all such possible causes and remedies, but the second issue above was very tricky to spot.

 

[Brooksie89]

I have a similar Beta and was concerned about dust shedding. Temperature test strips kindly supplied by Beta showed no problem, and the pulley bearing surfaces were free of any corrosion. Two things did the trick: (i) a cogged or notched belt and (ii) as a secondary issue, observing that at a particular and narrow engine rpm band the belt vibrated a little more than usual and was just catching the screw of a Jubilee clip on one of the engine hoses!

Forgive me if you have already been through all such possible causes and remedies, but the second issue above was very tricky to spot.

Thanks for the info!

What are the strips? The fundamental issue with mine is the temperature alarm on the panel does not work (bodgy installation by previous owner). All I have to go on is pipe temperature gauge clipped on after thermostat. An infra red gun says the block temp gets to 90 at full pelt on a hot day. So it could be fine, or not. The cheap guage reads something daft like 100+.

 

[Hydrozoan]

They were just small disposable strips to stick IIRC on the pulley(s). Lots around if you Google 'engine temperature strips' or similar, but I can't remember what their particular temperature range was - nor what was acceptable. I find Beta very helpful, so you could ask them.

In any event, the main cure for me was changing from a plain V-belt to a cogged/notched - IMO the 'gaps' in the cogged belt allow it to pass around a small diameter pulley with less distortion of the belt sidewall. If you have not already made that change, I very strongly recommend it in relation to dust shedding - assuming you've done things like removing any corrosion from the pulley surfaces. Until I made the change I was thinking of changing to a Beta poly-Vee system, but that is quite a cost - which the cogged belt made quite unnecessary.

I thought it worth mentioning the intermittent catching on the Jubilee clip because it was a devil to spot, and worth just having a look around the belt path, and observing at different rpm. Anyway, good luck.

 

[Hydrozoan]

Duplicate deleted.

 

[PetiteFleur]

With the coogged raw edge belts, they do transmit more horse power than standard vee belts. Much better than standard vee belts - Gates CRE belts are good.

 

[PeterWright]

Hi Hydrozoan,

Assuming the belt is correctly tensioned, a belt producing black dust has one (or sometimes both) causes. The first is the one you found, the belt is fouling on something that grinds material off it - I would include in this corroded, bent or misaligned pulleys. The second is retro fitting of smart alternator controllers, One of the key benefits of these devices is that they wind up the excitation of the alternator at low revs to almost the ratede power out of it whereas with a normal regulator the alternator will only produce full power at high revs. If you remenber that power = revs x torque, this means that the belt has to transmit more torque at low revs with the smart controller, which can exceed the belt capability leading to belt slip.

Whatever, it seems your belt problems had nothing to do with a hotter engine space as shown by the temperature strips Beta sent you.

Peter

 

[PeterWright]

Hi Brooksie,

90C is the right temperature for your block, the thermostat won't open until the temperature gets somewhere near that, so the cooling water is not flowing around the block. The temperatutre gauge will measure the temperature of the coolant flowing from the engine to the heat exchanger which should be around 90C.

I strongly suspect your belt producing black dust is some other problem, not heat.

Peter.

 

[Hydrozoan]

Hi Hydrozoan,

Assuming the belt is correctly tensioned, a belt producing black dust has one (or sometimes both) causes. The first is the one you found, the belt is fouling on something that grinds material off it - I would include in this corroded, bent or misaligned pulleys. The second is retro fitting of smart alternator controllers, One of the key benefits of these devices is that they wind up the excitation of the alternator at low revs to almost the ratede power out of it whereas with a normal regulator the alternator will only produce full power at high revs. If you remenber that power = revs x torque, this means that the belt has to transmit more torque at low revs with the smart controller, which can exceed the belt capability leading to belt slip.

Whatever, it seems your belt problems had nothing to do with a hotter engine space as shown by the temperature strips Beta sent you.

Peter

With apologies to the OP for further drift. I did indeed also check the alignment of the pulleys, which was fine. I have no smart alternator controller, but I believe the cogged belt worked for me - very little belt dust. The belt 'catching' was I believe secondary, and others on these forums have cited the benefits of cogged belts - worth using anyway for the trivial additional cost IMO.

PS Having said, I agree with you about the likelihood that Brooksie's belt problem is not heat-related - which is why I took the liberty of drifting the OP's thread to address that specifically.

 

[pvb]

The second is retro fitting of smart alternator controllers, One of the key benefits of these devices is that they wind up the excitation of the alternator at low revs to almost the ratede power out of it whereas with a normal regulator the alternator will only produce full power at high revs. If you remenber that power = revs x torque, this means that the belt has to transmit more torque at low revs with the smart controller, which can exceed the belt capability leading to belt slip.

The current produced by an alternator is dependent on the revs - it can't produce max current at low revs. "Smart" alternator controllers boost the charging voltage, which encourages the batteries to accept more charge, and can induce a bit more load on the alternator belt at lower revs. Most smart controllers have a built-in time delay before they start boosting, in order to give the engine time to warm up a little.

 

[Still Grinning]

Thread drift also provides interesting reading!

Thanks to the specific 331 answers - just to say that I have not had a problem with heat, but was just wondering if there was supposed to be a fan, as the larger Beneteaus have it, and I believe the American 331's have it.

My only (very minor) issue is that after a longer bout of motoring you do get the 'hot engine' smells (and I would say these are the normal smells you get from any engine that is working) transmitting up through the vents on the gangway. The very soon dissipate, especially when you open the forehatch and get a through-draft.

Thanks to all for the answers. Feel free to continue with Fred Drift!

 

[PeterWright]

... Fred Drift!

One of my best mates!

 

[jimi]

I’d say when the engine is running you don’t need it as the engine is sucking vast quantities of fresh air into the engine bay and then into the engine. Once the engine stops running it’s not going to get any hotter but may take a long time to cool. On my current boat with a larger engine there is a fan but I never use it