bilge blowers - how many and how are they configured?

dg775577

dg775577

New Member
Sep 12, 2010
17
South Central Indiana
Boat Info
268 Sundancer 1986
Engines
357 Mag Alpha 1
Hello all,
I have a 1986 Sea Ray 268.
It has a total of 4 vents with 4 inch hoses going into the engine compartment. It currently has 1 bilge blower.
I bought 2 new blowers and now I am wondering if it should have 4, one on each vent.
With 4 do they all blow out or are 2 blowing in and 2 blowing out?
If 2 is correct I am guessing that they blow out and the other 2 hoses are the intake air?
Also if 2 is correct where is the correct placement of them? Both forward, both aft, both starboard, both port?
Can't find in documentation to back this up.
Thanks in advance.
 
dg,
First...Welcome to CSR!

As for your question(s). I can't say for sure about your eaxct boat, but I doubt it ever had 4 blowers. I also doubt you'll find documentation to thier exact, original location.

I'm actually a little suprised it has 4 hoses. As for placement, the purpose of the blowers is to remove gas fumes from the engine compartment. That being said, the hoses that have blowers should be as low in the bildge as practical, and of course should be blowing out. As for placement you decide where is first... efficient to evacuate the fumes, and second... practical.

Again, welcome to CSR.
 
Yes...air in one side and out the other......arrange one or two blowers to exhaust out the same one side (maybe port) leaving the opposite side (maybe starboard) "open" for fresh air intake.
 
Thanks for the responses guys.
I think I'll put the blowers on the starboard side blowing out, that is the side the fuel filler is on.
After refilling the air will be blowing to the dock side making fume detection easier.
 
Yes you need four hoses because you have four louvers. Yes the hoses need to be low in the bilge to evacuate the heavy gas fumes.

I say you only need one blower because: The louvers need to be configured forward on the intake side and aft on the exhaust side. Put one blower on one exhaust hose. As your boat is under way, air will be scooped in from the intake side and drawn out on the exhaust side (via louver directional placement). You engine room will be vented constantly.

IMO: adding a second blower to the second exhaust hose will restrict the natural ability of the ER to breath while under way.
 
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Good point bonbini
 
+1 to what Ron said. I've only ever seen one blower used on small to medium sized boats. I've never looked on larger ones.

Don't quote me on this, but I do believe that one of the exhaust side holes should be left with no hose... or one that is only a few inches long. This way it would naturally evacuate from the upper level of the engine bay.
 
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Wow and odd.

I trust Dennis a lot.

His reply has me questioning if I am wrong.

OK, admitting up front that I am now second guessing myself due to Dennis’ post above….

On my starboard side I have two hoses; no blowers are in these two hoses. Air comes in on the starboard side through the vent and two hoses.

On my port side I have two hoses connected to a vent. Each hose has a blower, so two blowers. I am 100% positive each has a blower. I have had someone turn the blowers on and off as I touched them with my finger to confirm they are working. No vibration when off, vibration when on.



I have not modified this system; it’s this way from the factory.
 
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I'm basing what I am saying on what I've seen from the factory on a wide number of boats. I've seen it many different ways. Doug, don't second guess yourself - if you've got it that way from the factory, then you got it right. I suspect this may all come down to the exact specs/air flow of a particular boat and vent design/placement and that there is probably no one way that is correct for all boats. There's probably more variables at play here than we mere mortals know about!

I'm sure blower size/number of blowers is based on cubic feet of bilge space, but I wonder if it also has to do with single or twin engines? For what it's worth, my boat and the 268 are similar in size and I have only one blower (single engine).

If an engine room layout is available for your boat, with a single engine, DG775577, showing the proper placement... go with that. Of course, I don't think you can hurt anything if you install two blowers, both in the exhaust hose side.
 
Besides, I'm paying more attention to the baby-back ribs that are grilling right now on the barby, anyways! :grin:
 
Presentation said:
Wow and odd.

I trust Dennis a lot.

His reply has me questioning if I am wrong.

OK, admitting up front that I am now second guessing myself due to Dennis’ post above….

On my starboard side I have two hoses; no blowers are in these two hoses. Air comes in on the starboard side through the vent and two hoses.

On my port side I have two hoses connected to a vent. Each hose has a blower, so two blowers. I am 100% positive each has a blower. I have had someone turn the blowers on and off as I touched them with my finger to confirm they are working. No vibration when off, vibration when on.



I have not modified this system; it’s this way from the factory.
Click to expand...
I have two 4" blowers in mine. In my case both blowers discharge to port but one picks up from the port side and the other from starboard side.
 
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