WAJetboating
Member
One of the modifications I've been planning is some way to suppress the exhaust noise that comes into the passenger area via the floor drain. On my C2K, the starboard exhaust port is pretty close to the scupper valve. Off plane the scupper is still underwater, but once you're on plane (15-17 MPH and above) the scupper is above the waterline. It then becomes an excellent acoustic conduit for exhaust noise, straight into the passenger compartment.
I was amazed at how much sound was coming in that way. Normally I'm the driver, but as our son has gotten into wakeboarding my wife has done more of the driving so I can coach. Being in the driver's seat concealed a lot of the noise, but once I was sitting anywhere else the volume level was surprising. I took to blocking it with a towel - but that defeats its purpose as a drain.
Big dilemma: How to block the sound without blocking the water flow? My answer was to create a plumbing trap, like those under a sink. While sound (technically, alternating pressure waves) travels quite well through water - actually faster than through air, since water is a denser medium - the waves need to be introduced to the water in an efficient manner. An air-to-water-to-air coupling is quite inefficient (technically, the two interfaces have high impedance) so a "plug" of water should block sound waves quite nicely without much affecting water flow.
My initial approach was going to be lengthening the bilge hose and using tyraps to form a "U" from the hose itself. However, it turns out that the C2K's bilge hose and scupper valve are 1.5 inches ID. Magically, 1.5 inch plumbing traps are 1.5 inches OD. A perfect fit. This avoids the somewhat dodgy tyrap approach in favor of something designed specifically to accomplish the objective.
A short piece of stiff EDPM hose later, and here was the result:
The stiff EPDM hose provides mechanical support to the trap. The trap also rests against the inner hull to prevent stressing the joints as the boat bounces around. The trap is reversed from its normal orientation to allow for the boat's normal bow-elevated attitude; this arrangement increases the volume of water that is "trapped" within.
While I was at it, I also removed the scupper valve for cleaning. Mine is the ping-pong ball style, and the little gasket often gets dirty. I'm glad I removed it, because when I disassembled it I found that a piece of plastic almost the entire diameter of the valve had gotten stuck inside. Presumably someone had dropped something on the floor of the boat, and it had been carried by draining water to the scupper valve where it was too large to exit. Thus I'd had an artificial restriction in my scupper valve for who knows how long. That alone made this project worthwhile.
Another interesting detail was that Seadoo didn't bother to use any sort of sealant on the scupper valve, instead relying solely on the gasket that came with it. I'd noticed a slight water seepage around the scupper valve, and this explained why. A quick trip to West Marine for a tube of 3M's 4200 marine sealant fixed that. I roughened the gelcoat under the scupper valve, ran a light bead of the 4200 on its outer mating surface, and pressed/rotated it into the hole. The 4200 squished out evenly all around the valve so I knew I had a good seal. I installed the gasket and tightened the nut, then reattached the bilge hose with two stainless steel hose clamps.
I then tested it for drainage by dumping full five gallon pickle buckets into the passenger compartment. I had the boat angled to the starboard side and bow up, so the water would naturally flow toward the drain. It drained so fast I wasn't able to keep the water level high enough to submerge the floor drain - there was always some air space in the inlet. I didn't do a formal flow test but based on how fast five gallons emptied out I'd say it drains 7-8 gallons per minute. The biggest restriction is likely the scupper valve because it has a far smaller cross section than does the 1.5 inch trap and 1.5 inch hose.
Then I tested it for acoustics. While my son was lying under the boat holding the scupper valve open, we both tried yelling to each other through the tube. We couldn't hear anything through the tube at all.
I consider this a solid improvement to the boat. Cost was about four dollars for the trap components, and a few more dollars for the stiff hose and stainless steel hose clamps, for a total of less than ten bucks. The 3M 4200 costs about $14 but isn't strictly necessary because you don't need to remove the scupper valve to make this mod. I just figured there would never be a better time to insure that fitting was watertight to the hull.
Hope this helps someone!
I was amazed at how much sound was coming in that way. Normally I'm the driver, but as our son has gotten into wakeboarding my wife has done more of the driving so I can coach. Being in the driver's seat concealed a lot of the noise, but once I was sitting anywhere else the volume level was surprising. I took to blocking it with a towel - but that defeats its purpose as a drain.
Big dilemma: How to block the sound without blocking the water flow? My answer was to create a plumbing trap, like those under a sink. While sound (technically, alternating pressure waves) travels quite well through water - actually faster than through air, since water is a denser medium - the waves need to be introduced to the water in an efficient manner. An air-to-water-to-air coupling is quite inefficient (technically, the two interfaces have high impedance) so a "plug" of water should block sound waves quite nicely without much affecting water flow.
My initial approach was going to be lengthening the bilge hose and using tyraps to form a "U" from the hose itself. However, it turns out that the C2K's bilge hose and scupper valve are 1.5 inches ID. Magically, 1.5 inch plumbing traps are 1.5 inches OD. A perfect fit. This avoids the somewhat dodgy tyrap approach in favor of something designed specifically to accomplish the objective.
A short piece of stiff EDPM hose later, and here was the result:
The stiff EPDM hose provides mechanical support to the trap. The trap also rests against the inner hull to prevent stressing the joints as the boat bounces around. The trap is reversed from its normal orientation to allow for the boat's normal bow-elevated attitude; this arrangement increases the volume of water that is "trapped" within.
While I was at it, I also removed the scupper valve for cleaning. Mine is the ping-pong ball style, and the little gasket often gets dirty. I'm glad I removed it, because when I disassembled it I found that a piece of plastic almost the entire diameter of the valve had gotten stuck inside. Presumably someone had dropped something on the floor of the boat, and it had been carried by draining water to the scupper valve where it was too large to exit. Thus I'd had an artificial restriction in my scupper valve for who knows how long. That alone made this project worthwhile.
Another interesting detail was that Seadoo didn't bother to use any sort of sealant on the scupper valve, instead relying solely on the gasket that came with it. I'd noticed a slight water seepage around the scupper valve, and this explained why. A quick trip to West Marine for a tube of 3M's 4200 marine sealant fixed that. I roughened the gelcoat under the scupper valve, ran a light bead of the 4200 on its outer mating surface, and pressed/rotated it into the hole. The 4200 squished out evenly all around the valve so I knew I had a good seal. I installed the gasket and tightened the nut, then reattached the bilge hose with two stainless steel hose clamps.
I then tested it for drainage by dumping full five gallon pickle buckets into the passenger compartment. I had the boat angled to the starboard side and bow up, so the water would naturally flow toward the drain. It drained so fast I wasn't able to keep the water level high enough to submerge the floor drain - there was always some air space in the inlet. I didn't do a formal flow test but based on how fast five gallons emptied out I'd say it drains 7-8 gallons per minute. The biggest restriction is likely the scupper valve because it has a far smaller cross section than does the 1.5 inch trap and 1.5 inch hose.
Then I tested it for acoustics. While my son was lying under the boat holding the scupper valve open, we both tried yelling to each other through the tube. We couldn't hear anything through the tube at all.
I consider this a solid improvement to the boat. Cost was about four dollars for the trap components, and a few more dollars for the stiff hose and stainless steel hose clamps, for a total of less than ten bucks. The 3M 4200 costs about $14 but isn't strictly necessary because you don't need to remove the scupper valve to make this mod. I just figured there would never be a better time to insure that fitting was watertight to the hull.
Hope this helps someone!
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