Saltwater Protection: Change Your Anodes, Flush Your Engine

A lot of boats end up sitting in salt water all summer, and if yours is one of them — or you just bought one — there are a number of things to consider to keep trouble at bay.

Sitting in the saltwater for extended periods eventually takes a toll on the sterndrive and other exposed components on the transom.  Your best bet is to to pull the boat out periodically to clean and inspect the drive, the transom assembly, and your trim tabs if the boat is equipped with them. Mercury Bravo sterndrives are equipped with the MerCathode system, and they’re optional on Alpha drives. If yours drive doesn’t have the system, look into it.

By using a muff-style flush kit, you can get an idea how well your sea pump is working.

By using a muff-style flush kit, you can get an idea how well your sea pump is working.

At a minimum you should replace the zinc anodes on the drive regularly. On a Bravo drive, for example, there’s one anode in front of the propeller attached to the prop-shaft bearing carrier, and two more on the front and rear of the cavitation plate. The trim cylinders also have anodes on the aft end.

It’s also a good idea to install a freshwater flush system that allows you to flush the engine while the boat is in the water. Even if you have a closed cooling system, the sea pump, heat exchangers, and exhaust are exposed to salt water.

When you get the boat on a trailer, the best flush kit fits over the side water pickups on your drive. Lots of builders will provide a hose fitting conveniently on a bulkhead around the engine compartment, but the “muffs” that go over the drive are better, and for a reason you might not expect.

By using the muffs, you can get an idea how well your sea pump is working. If there are any signs of trouble, like a broken impeller or one that’s missing a blade or two, it will show up in the pump’s inability to draw water up the drive. The water flow out the propeller or exhaust will be reduced, which is something you can see. That doesn’t happen with a bulkhead-mounted fitting.

For Mercury engines, the part number for the muffs is 44357T2. It has the wire that pushes through the drive and the metal tab that holds it in place. It’s less than $30 and is money well spent.