Water leaks are a common problem on any boat that typically are easily resolved. Here are the most common causes:
Most common - Water and Holding Tanks which all have inspection ports tend to consistently have problems especially for new owners who are not aware of the issue.
a. First check water tanks under aft bunks. The inspection port should be cleaned and sealed with good sealant to keep them from leaking. Do not depend on them staying water tight without some goop on them.
b. Next is more difficult to check, the holding tank Inspection port (this water comes with smells) and is not accessible on my boat anyway. You must remove the step in the sail locker to reach it. See Nature Head conversion story for details on this.
2. Very common – Forward drain for sail locker leaking water thru floor into forward floatation tank. Just stick a plug in the sail locker drain hole and forget it.
3. Fresh water pressure system leaks which require regular at least annual checking.
a. Water hose clamps all need to be tightened each season a the temperature changes from winter to summer tend to loosen them.
b. Foot Pump - Unless you use this pump which few of us do, just take it out of the line and remove one source of potential leaks.
4. Deck leaks which are very common from the chain plates and winches. These will need to be rebidded from time to time. I like to use Captains Creeping Crack sealant to delay the chain plate rebedding a few years.
a. Typically the Chain Plates will need to be rebidded every 2-5 years which involves removing the sealant caps, removing the old calking and resealing with new sealant. There is debate about which does best, but most rigger I know recommend Lifecaulk sealant over 5200 or 4200 for most situations. All will work for a time and I think it is more dependent on how clean you get the surfaces before re-caulking as well as how often you sail in heavy weather which tends to break the seal.
b. Winches will typically break the seal every few years and need to be removed and rebedded, but this really depends again on how often you do some heavy weather sailing which puts a heavy strain on the mounting. Note the winch on port leaks directly on the stereo and will disable it from my experience. Make sure you replace the stereo with a marine version that has a plastic drip guard on top of it.
5. Water heater due to rust. After a few years the water heater will rust through and begin leaking. I believe about 8 years is about when mine was looking so bad I decided to replace it with a stainless steel insulated model which I relocated to the engine compartment after switching to outboard.
6. Sea water pump seal dripping water under engine is really common problem and started almost immediately with my engine. There is a write up on the seawater pump replacement.
7. The stainless steel centerboard bolts from time to time will rust enough to begin leaking or even have the head pop off. These bolts are best replaced with silicone bronze or titanium if you can find the right size. If your boat is more than 7 years old and still has the original bolts, I would just go ahead and replace them at your next haul out and remove the drama of having them fail while underway. I also replaced the standard plywood washers with G10 which should not need replacing for the life of the boat, nor hopefully will the silicone bronze bolts.
8. Thruhull hose clamps rarely leak, but should be inspected monthly and replaced if showing any signs of rust or corrosion. There should be two clamps on every thruhull hose.