Engine Vent Fan

[Seahawk345]

Yanmar 3YM20
Hope someone can shed some light on this topic.
Last year I bought a 2010 Hunter 31 with a Yammer 3YM20 engine. There is an engine room vent fan that comes on as soon as the engine starts, and runs continuously as long as the engine is running.
There is no breaker or switch that I can find anywhere to turn the fan off. I have read in a couple of places that this is normal, and the fan is there to vent out hot air and keep the engine running cooler and that the system was designed like this.
if thats the case then I'm OK with that,.....even though the little fan is quite loud and can be heard quite clearly in the cockpit while motoring along.

Can anyone either confirm or deny that this is the way its supposed to be......??
And if it is intended to be turned off, is there a switch somewhere that I'm missing..??? Or has anyone installed a breaker on the panel to enable control of the fan,

Thanks for any help or advice.

Jim

 

[ggrizzard]

Sounds like the fan is hard wired to the ignition circuit. There is no safety issue
with putting in a separate circuit and a switch that I know of.
Perhaps they did it the original way so that operators wouldn't have to remember to turn
the fan on manually before engine start-up.

 

[Calif. Ted]

Most are on the ignition circuit so run while switch is on, Catalinas have a switch on bottom of engine panel so it can be switched off. Jeanneau and Beneteau do not have a switch. I don't know how Hunter wires it.

 

[tfox2069]

Sounds like the fan is hard wired to the ignition circuit. There is no safety issue
with putting in a separate circuit and a switch that I know of.
Perhaps they did it the original way so that operators wouldn't have to remember to turn
the fan on manually before engine start-up.

That's how it is wired on my MH40. i had to replace the fan which died in an aurally spectacular fashion last season and it's definitely wired to the ignition circuit. There's no breaker, but it is fused. Pretty easy to replace if you can get to it. You can probably find a quieter fan than the cheap stock one that came with the boat. The one I replaced it with is significantly quieter.

 

[Roland5048]

From what I have always believed, the engine room fan is used to evacuate gasoline fumes before turning the ignition key to prevent an explosion. Not necessary with a diesel engine but doesn't hurt, either. If your engine compartment is really tight, (who's isn't?), and enclosed then I would think a fan does help keep it a bit cooler in there. As @tfox2069 suggested, just install a quieter fan.

 

[Hello Below]

Can anyone either confirm or deny that this is the way its supposed to be......??

Confirmed . . . but only for a 2012 H33 (Yanmar 3YM30). There should be a little push button reset (breaker only) on your dc panel labelled BLOWER. To make it switchable, you could use a spare switch/breaker on the panel so you could easily wire it as an “AND” function (ie the engine is on AND the switch/breaker is on). Then add a “Blower” label and Bob’s your uncle.
Switch/Breaker SPST
DC Panel Label - Blower

If you want to get fancy, you could have the blower (actually a sucker) only come on at a set temperature.
I have all the parts to control the engine room blower with a temperature controller (Inkbird ITC-1000(12V)) but have yet to install.

 

[tfox2069]

One other note that just occurred to me. My 2009 Hunter 36 had the 3YM30 engine compartment fan on a switch at the breaker panel where I could turn it on or off at will, and it was NOT wired through the key initiated ignition switch. My 2015 MH40 is wired with the ignition switch, though there is no key for the later boat, just a push button. Don't know that any of that is helpful, but assuming both boats came from the factory like that (and I have no reason to believe they did not), then Hunter did change the way they wired those fans up over time. With the engine running the fan doesn't really add much noise so it's easy to ignore, and does vent some heat. But agree with @Roland5048 on the typical purpose on a gas engine, and his point that it doesn't apply to a diesel.

 

[Seahawk345]

Thank you very much everyone for all the input. Theres a wealth of knowledge on this site, and the input is appreciated. From the comments it sounds like it should be OK to install a switch or breaker but I might just go with the option of finding a quieter fan first. Thanks for all the help..... J.

 

[rgranger]

I like the idea of having your blower on a thermostat. Seems like you would want it to automatically come on if the space starts to get hot.

These wafer stats are dirt-simple and take 5 min to install... no moving parts or circuit boards to wear out.... robust as hell. The wafer expands and contracts with temp. and opens or closes the circuit.

I used to raise chickens and I used these in the hen house to turn on/off heat lamps.

https://www.amazon.com/GQF-Wafer-Thermostat-Assembly-Incubator/dp/B00AIQ1REY/ref=asc_df_B00AIQ1REY/?adgrpid=60862048959&gclid=CjwKCAiA_OetBhAtEiwAPTeQZ96hVa6jzzL79DN6n_tMcSQaaD1S1q69cmteCyCREMaUz934PqHIEBoCSXIQAvD_BwE&hvadid=309750302298&hvdev=c&hvdvcmdl&hvlocint&hvlocphy=9010488&hvnetw=g&hvpone&hvpos&hvptwo&hvqmt&hvrand=5031411810926277835&hvtargid=pla-571718868435&linkCode=df0&mcid=4bb6f0337e973cbb8ac7519d01b4b209&psc=1&ref&tag

 

[Davidasailor26]

One other thing to consider if you’re changing the wiring - I’ve often thought it would be nice to keep the fan running for a few minutes after shutdown, to exhaust more hot air when anchoring out in the summer. If the fan is just wired to the ignition or with a thermostat in series there’s no good way to let it keep running.

 

[dlochner]

The blower fan does very little to cool the engine room. At operating temperature there is 400 lb block of aluminum or steel at about 180° F. A 3in diameter fan is not going to do much. And if the fan is installed to be an exhaust fan it will be competing with the engine for air. On the other hand if the fan is set to force air into the engine room it will pressurize the room and any odors in the engine compartment will be forced out into the cabin.

Engine room venting is necessary because the diesel will consume a lot of air, this can be passive venting through the hose and other open areas around the engine room.

I never run the fan because it is obnoxiously noisy and I've never had an overheating issue.

 

[Hello Below]

Some thought provoking points from posts 9, 10 and 11. My 4" exhaust fan hose is positioned directly above my Balmar alternator and the fan only comes on when the engine is running (wired through the ignition). When heavily loaded (and belt managed to 3) the alternator temperature rises to very close to 100° C when the exhaust fan is off or 80° C if on. I have not knowingly had a problem with starving the diesel of air. I would also like to keep the fan running after the engine is shut down when moored. Although the wafer thermostat seems to be difficult to come by, maybe something like this would substitute:
Mechanical Thermostat, 0-60 Adjustable Normally Open Temperature Controller Switch(KTS011)

 

[rgranger]

Although the wafer thermostat seems to be difficult to come by, ...

I provided the Amazon link in post #9

 

[Hello Below]

I provided the Amazon link in post #9

Yup went there. For most items Amazon.com will ship to a Canadian address but not in this case. Amazon.ca does stock it but totalling over $60 (Cdn) it’s a bit rich for an experimental item. So for $10.25 (Cdn) I will give the alternative a try and report back.
Thanks for planting the seed though.

 

[Rich Stidger]

If you have a compartment heat-triggered fire extinguisher, having the fan exhaust hot air directly from the hi-output alternator is a very good plan. I had a fire-extinguisher trip due to the radiated heat from the alternator. An exhaust fan pulling air from around the alternator fixed that issue.

 

[rgranger]

Yup went there. For most items Amazon.com will ship to a Canadian address but not in this case. Amazon.ca does stock it but totalling over $60 (Cdn) it’s a bit rich for an experimental item. So for $10.25 (Cdn) I will give the alternative a try and report back.
Thanks for planting the seed though.

Ah! Didn't realize there were customs issues. Strange? I wonder why something so simple would be restricted.

 

[Hello Below]

Ah! Didn't realize there were customs issues. Strange? I wonder why something so simple would be restricted.

I don’t think the item is restricted per se, I think that it is the seller that simple does not want the hassle of shipping outside the US. Yes there would be a customs form to fill out but no doubt there would be zero duty/customs fees as it is well under our deductible.

 

[dlochner]

Ah! Didn't realize there were customs issues. Strange? I wonder why something so simple would be restricted.

All goods shipped across the border in either direction make a stop at the customs office. Recently I mailed a T-shirt to a friend in Canada, I had to declare the contents and the value. It also increases shipping time. If duty is owed the recipient must pay the duty before delivery. Some larger commercial business, Binnacle.com have a shipping arrangement with UPS that expedites shipping or they open a US warehouse to ship from.