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#1
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Bilge Blower install help
My son just picked up a 88 I/o V20. The engine is pulled and being rebuilt. There isn't a blower in there at the present. I don't see a place for the exhaust hose either. Where is the blower normally placed and is the hose just routed up to the port or starboard vents? Thanks for any help.
-Robert 
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#2
10-29-2013, 02:19 PM
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IF there is a bilge blower (lots of IO's don't have them) the placement of the hoses is really up to you. Normally you would see two vents on your gunnels, one on the port and one on the starboard side, towards the stern, just before the transom. One will have the vent vanes facing forward, the other will have the vent vanes facing rearward. The idea being that as you move through the water the air will enter through the forward facing vent and exit through the rearward facing ones, thereby venting your bilge automatically. Most powered bilge blowers exhaust through the rearward facing vents. But the decision as to where to place them is entirely up to you. The idea of course it to make sure that your bilge is vented of any explosive vapors before you start your engine. Since most modern engines have fuel injection now, the chances of a harmful build up of gas vapor are slim at best. Baring leaks in your fuel system, (at which point you should NEVER take your boat out on the water) there's really no place for the vapor to come from. I know that a lot of people will disagree with me, but when I had an I/O powered boat I never bothered with a bilge blower. All I did was lift the engine hatch before trailering the boat to the launch ramp. I figured that any vapor that might have accumulated would be long gone by the time I got to the ramp. Since there was never an explosion, I'm guessing it was a good decision. Understand, I'm not saying bilge blowers don't have their place, I'm just saying that with normal, prudent, safety precautions I think their usage is minimal at best.
__________________
1987 V20 w/1987 150HP Yamaha on a Shoreland'r Trailer 1978 16.5 Airslot w/1996 120HP Force on a Four Winns trailer 1996 V21 w/1993 200HP Mercury on a Shoreline Trailer All towed by a 5.7L Hemi Durango. If God didn't have a purpose for us we wouldn't be here, so Live simply, Love generously, Care deeply, Speak kindly. (Leave the rest to God)  Silence, in the face of evil, is itself evil. Not to speak is to speak, not to act is to act. God will not hold us guiltless.
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#3
10-29-2013, 02:48 PM
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Both of the vents on this boat face backwards. My bass boat has one forward and one backward. The v20 will be an ocean boat though and I think I'd rather keep them facing the way they do so salt water spray doesn't get channeled into the engine compartment.
The way this boat will be used it will be started multiple times a day and the thought of lifting the engine hatch each and every time just doesn't appeal to me. I've seen a few pictures of what can happen when there is an explosion. Not a pretty site. If we are going to put one in now is the time as I can't use the boat anyway. Of course the first I/O my family had when I was young didn't have a blower (not sure any boats did back then) and it didn't blow up. Easily could have though as I did have an uncle pump 30 gallons into the bilge through a rod holder once. -Robert
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#5
10-29-2013, 04:02 PM
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i was at the marina one day waiting to get gas, holding on the sea wall. there was a sea ray i/o tied up at the pumps. guy comes running down to move it, jumps in, hits the key, boom. his buddy was sitting on the hatch cover. threw him about 15 feet in the air and in the water. nobody hurt, mostly flash & noise, but it made an impression on me.
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#6
10-29-2013, 08:07 PM
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My 77 has three vents, one in the center facing forward and two facing to the rear. My blower is mounted below the one facing to the rear on the starboard side. I usually open the engine cover before starting and run the blower in extremely hot weather. It seems to keep the engine cooler. In N.C. its a law, you gotta have a working blower on a I/O boat. My vents have large hoses that go down into the bilge.
__________________
 77 V20 cuddy with 170 I/O Mercruiser 72 16ft. Carolina w/a 25hp Evinrude
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#7
10-29-2013, 08:56 PM
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put a blower in it and operate it for several minutes before starting and while at idle or no wake speed.
the intake should go to the lowest part of the bilge NOT likely to have standing water... definitely below the starter. as for fuel injection or carb makes no difference... fuel lines filters fill hoses vents and even tanks can leak..... heck the fuel tanks are a COMMON issue with these boats
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#8
10-29-2013, 11:47 PM
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Since my boat was constantly being run/trolled the only time I lifted the engine hatch was during trailering. By all means, if you want to install a bilge blower, then do so. An ounce of prevention, as they say..... And as to your uncle pumping 30 gallons into the bilge thru a rod holder, it's really amazing how many stories like that we hear of. And truthfully, in that situation, the best bilge blower in the world won't help you at all.
__________________
1987 V20 w/1987 150HP Yamaha on a Shoreland'r Trailer 1978 16.5 Airslot w/1996 120HP Force on a Four Winns trailer 1996 V21 w/1993 200HP Mercury on a Shoreline Trailer All towed by a 5.7L Hemi Durango. If God didn't have a purpose for us we wouldn't be here, so Live simply, Love generously, Care deeply, Speak kindly. (Leave the rest to God) Silence, in the face of evil, is itself evil. Not to speak is to speak, not to act is to act. God will not hold us guiltless.
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#9
10-30-2013, 12:27 AM
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you also said people would disagree with you... lol ... you were right BUT I do see your point about the carb vs FI AND I totally agree that you should never knowingly operate a boat with a fuel leak but sometimes you don't know... IE the first pin hole in an aluminum fuel tank... sometimes people don't find the leak till they see a sheen on the water from the bilge pump discharge....
I'll add though that since the FI runs at a higher pressure and that it uses an electric pump one MIGHT argue that it introduces a new risk all it's own... Also the O/P doesn't have FI anyhow all in all I feel that the chances of catastrophe are very low and I often start the engines without running the bilge blowers if they haven't been off long and when I trailer to the ramp I figure that cruising down the road will ventilate the bilge just as well as cruising up the river... BUT I also have a fume detector I installed with an alarm and the ability to automatically activate the blowers at IIRC 10% of the LEL
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#10
10-30-2013, 09:57 AM
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As far as the directions of the vents, I wasn't concerned with water pouring into the bilge but just some spray dripping into the engine compartment. I figured it was best to keep as much salt water out as possible even if it were just a small amount.
I can see the point about it ventilating the bilge very well on the way to the ramp when one vent is facing forward but when running out on the water the engine will clear the bilge better than any vent. I'll probably turn one of them around and add a blower.
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