Another area to check for leaks is where the impeller shafts come through the hull to the intermediate bearing/coupler, which is protected by a short hose and thru hull fitting. Inside of this hose stays wet and submerged when in the water, so seal is critical. Since I've bought my boat I've always had 3-4 gallons come out almost every time I pull the boat out of the water, basically everything that sits in the keel that the bilge can't pump. I've checked many of the things in this thread with no obvious leaks of significance. In my case, it only seemed to accumulate water when the engines were running. I could leave it wet slipped and off all weekend and the bilge didn't seem to ever kick on, but if I ran the boat at speed for 5 minutes, it would almost always kick on the bilge once I stopped and moved to the back of the boat, shifting the weight, and water, to the bilge. I've had the issue since I purchased, but it had slowly gotten worse, with the bilge kicking on more and more often. Heading to Bimini in a few weeks for 7 days, so was determined to get it as dry as possible.
Got poking around one day on the water and noticed water leaking from the seal between the plastic thru hull sleeve and rubber hose on both the port and starboard side. The area had a ton of haphazardly placed silicone around it, but it was easily peeled off by hand and obviously wasn't adhering to the fiberglass or sealing anything. Tried tightening the hose clamps first with no improvement. As mentioned, it wouldn't noticeably leak sitting still, but under power it did. Assuming the spinning shaft inside of the hose increased the pressure some, pushing water past the seal. Ultimately ended up pulling the pumps, pulling the thru hull sleeve, cleaning off the clear silicone and mating surfaces, and reapplying 3m 4200 sealant on both the face of the fitting and inside of the rubber hose. A couple of the screw holes were stripped out seemingly from the factory, so I used the next size up (#10 vs [HASH=6666]#8)[/HASH] and made sure they were sealed with 4200 as well. Should of done it a long time ago, whole thing only took 2-3 hours, with taking my time.
Got it back out on the water for the July 4th weekend. Boat stayed in the water 3 days and had 6-10 kids on and off all weekend pulling tubes and water on the swim platform constantly. Checked through the access port as best I could and didn't notice any obvious leak. When I pulled it out of the water Monday and pulled the plug it wasn't bone dry, but was a fraction of what I typically see. I think most of what was in there leaked around the access port with all the kids on and off the back so much and the wet storage tray staying soaked. Also never noticed the bilge kicking on even once the whole weekend, which hasn't happened in a long time. As little water that came out, I don't think it ever made it to the bilge. Hoping to get it out this weekend and see how much of an improvement it makes on a 1 day trip without as much activity on the swim deck.
Here's how it was from the factory. You can see the poorly applied silicone on the left and obvious runs from the leak. This is the port, but both side looked and leaked the same.
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Here's the nasty silicone I peeled off, largely by hand. Zero adhesion or sealing.
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Here's what the plastic thru hull fitting looks like removed and cleaned up.
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Here's where the fitting goes. It was a pain to remove all the old silicone from this area as it's just hard to reach. Ended up using a brass wire wheel to clean it up after getting what I could off with a razor blade. Top screw hole was stripped out for the factory #8 screw, so used a #10 screw on reassembly.
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Here's the reassembled connection from the cleanout. Notice the white 4200 peaking out of the hose
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Here's the reinstalled fitting in the pump tunnel, again, notice the 4200 peaking out of the edges.
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