Posted: April 1, 2013
If it’s time to replace your current unit, you don’t have to pay to get it done.Water heaters crash for a variety of reasons. A failed heating element can often be repaired by replacing the defective parts. More serious is failure from freeze damage, which can split the water tank when the water in it expands. Often, water heaters are located in out-of-the-way places in the boat, and the damp environment can cause corrosion, rust and eventual failure as well.
Replacement is well within the capabilities of the average boat owner. If you can operate a screwdriver and a wrench or two, you can probably change a water heater in a day. Some units are buried in spaces that may require you to dismantle other components to get enough access for removal. It’s not uncommon to have to remove exhaust hoses, engine manifolds or other components on smaller boats just to get access to the unit. So be sure you’re comfortable with all of the required tasks before tackling the job.
Once you’re sure you have access, you’ll need to unhook the plumbing. On most boats, you’ll notice four connections. Two are for the potable water: cold water in, hot water out. The second set is for lines from the engine. These lines carry engine coolant to the heat exchanger built into the tank, which allows the water to be heated by waste heat generated by engine operation. Don’t confuse the two sets of lines.
You’ll need to capture the coolant that will drain from the engine heater hose, as it is poisonous and should not be allowed to mix with bilge water and pumped out of the boat. A hose connector can be used to connect the two hoses to each other to prevent excess coolant loss while the water heater is being replaced. These lines are usually clamped onto tubes on the water heater. Use the same clamps on the hose connector to prevent leaks. Check the hose size (it should be printed on the hose itself) to get the right size coupler before you start.
Make sure the freshwater system is turned off before you disconnect the potable water lines. There will still be some water loss, but this water can drain to the bilge — unless your bilge is bone dry and immaculate. In that case, capture this water as well. And there may be a lot of it if the tank still has water in it. Most tanks have a water drain built into them for winterization purposes, so you will be able to get most of the water out of the tank.
Make sure the AC power to the tank is shut off, too, and open the panel that the wire goes into. There will be three wires to disconnect, usually black, white and green. Make note of any labels on terminals that these are attached to. You’ll want to duplicate the connections on the new unit. Properly wired boats will have a green ground wire, a black hot wire and a white neutral wire.
There may also be a bonding wire attached to the exterior of the heater itself. Don’t confuse this wire with the green wire that is part of the 110v electrical wiring.
After disconnecting all the plumbing and electrical, you need to remove the water heater itself. It should be fastened to the platform it sits on, or it may be strapped in place. If the replacement unit is the same dimensions as the existing water heater, you can reuse the old mounting components. If the new unit is different in design, you need to be sure it is mounted securely in the location.
Once the old unit is out and the shiny new water heater is securely in its place, reconnect all of the plumbing. Now is the time to replace any questionable components, especially if this is a hard-to-reach area on the boat. Reconnect the wiring. Check for loose connectors and replace as needed.
Turn the pressure-water system back on and open a faucet to allow water to fill the tank. Never turn the AC power on to the tank when it is empty, because it can damage the heating element. When a clear stream of water comes from the faucet with no air, turn the faucet off. The water system should pressurize, and the pump should cycle off. Check for leaking connections on the potable water.
Start the engine that the water tank exchanger is connected to. After running it for a few minutes, check the coolant to be sure it is at the proper level. Add coolant as needed (usually equal to any coolant lost during removal). Be careful, as the coolant will be hot! Check for coolant leaks at the water heater.
Once you’re sure there are no water leaks, turn the power on for the unit and the electrical panel. If the breaker trips, you’ve wired the unit incorrectly. Once the power is turned on, wait for a while and check for hot water at the faucet.
Once you have hot water at the faucet, you can return to more civilized time aboard the boat. And enjoy a shower in the morning.