bilge blowers??

[markawilson]

I am embarrassed to ask this question but I can't seem to find the answers and hope somebody can clue me in. On my 1990 41c I have blowers on each side with the hose leading to underneath the engines. Do these blowers blow outside air into the engine room or do they suck hot engine room air out? I noticed how hot in the summer the engine room can get and would like to leave the blowers on for some period of time to cool off the engine room - is this recommended? Is there a problem with leaving the fans on for hours at a time? Should I take the 4" dryer-vent looking hoses off the fans? Thanks for the comments!

 

[MikeP]

They pull air from the lower portion of the engine room - where dangerous fumes can gather, and exhaust it outside. They are not designed for and are not effective at cooling the eng room.

To do that you need to install a separate blower system that pulls air from the highest point in the engine room and exhausts it outside. Typically these are dual squirrel cage blowers mounted on the ceiling of the eng room; they exhaust the air out through a plenum via the engine air intake vents. They can be left on as long as you want.

 

[Will]

I don't know about your particular model of Hatteras but generally, blowers blow air out. The dryer hose should extend to a low point in the bilge. I believe these to be ABYC requirements. As for heat in the engine room, it shouldn't hurt to run the blowers if you like but I don't think that the heat after the engines are shut down will cause any problems. However, if it makes your boat interior too warm then maybe using the blowers to cool things down may be a good idea.
Will

 

[Finalee]

The primary purpose is to remove fuel vapors. Gas vapors are heavier than air and collect in the bilge. Gasoline being very combustible is a special concern. Be certain the system is working correctly and used before the engines are started. I was especially paronoid when I owned gas powered boats and would actualy wait until the air being exhausted out the vents smelled clean. If in doubt go below and check it out. Good motto when you aren't sure that the bilge is gas free.

 

[Fanfare]

The blowers exhaust fuel vapors from the bilge. But they draw in cooler air from outside via the engine room intake vents. So running them is some help for cooling the engine rooms. Not as good as blowers mounted on top where they pick up the warmest air, but you have these installed now--give it a try and see if it helps.

The Coast Guard requires blowers on all boats. They are essential for gas engines as the vapors collect in the bilges. (But if there is a gasoline leak you could run the blower all week and it wouldn't clear the problem.) If you have diesels I have seen people pull the dryer hose off the high-mounted vent fans and get at the hot air that way.

 

[GaryNW]

The typical bilge blowers on the market are not intended for continous duty and would probably need fairly frequent replacement if run for hours at a time. On the other hand, if you price out continuous-duty dc motors, it might be cheaper to just go thru a bunch of std bilge blowers. I believe they fail "safely" when they do wear out.

When I bought my boat in July, one blower was frozen and the other ran at maybe 100 rpm with a screech. The PO admitted he never used them. I stated that I always use them! He bought new ones as part of paying for all safety related issues.

Gary

 

[yachtsmanbill]

I think the greatest mis-conception about blowers on a gas boat are just to ventilate fumes, and that part is good. What a lot of folks dont realize is when you shut the engines down, the gas BOILS out of the carbs in the form of vapor and goes south... Thats why its so imperative to run the blowers even after a lengthy dock session. Those fumes will linger for ever with no way to extract them except for the blower.
My Roamer, and all other gas boats for that matter have forced ventilation for underway and when you are reduced to idle speed, its recommended to run the blowers. If you look at your forced ventilators, they are boxed or hosed to the bottom just for this purpose, BOTH the in's and the out's.
FWIW THIS INCLUDES GAS GENERATORS AS WELL !!
Part of the rebuild on the Hatteras is to leave the pre-existing 110VAC blower from the center head in place to use as a cool down blower. Either rig it on a switch, thermostat, or a timer. When the 12s are running there is a lot of air moving, but shut them down and it gets pretty warm in a hurry! ws

 

[REBrueckner]

You don't say whther your boast is gas or diesel. I'd definitely leave them in place for use as others have posted.

If you'd like to cool your engine room, there is a much simpler way. Just stick a 12 volt fan down low where it can pull in cool air from outside into the engine room. This will aid natural convection cooling significantly.

On my 48 YF, I have a portable 12volt fan under the steps forward in the engine room at lower galley/forward stateroom level and leave my engine room entry door (under the steps, maybe 24" x 24" square) open. In hot weather at anchor I can open the forward hatch and let breezes push air thru the open engine room door and up and out the side hull intakes, or if it's still or raining, I leave the fan on for an hour or two....you can really feel the difference the open hatch or fan makes by feeling air as it exits the hull vents on either side. This keeps the saoln above cool and keeps engine room batteries cooler as well.

In cold weather, I put the fan inside the engine room, and blow warm engine room air out into the lower galley/forward stateroom level forward...you can get up to eight hours warm air/free heat when desired.