If it isn’t the gas, it’s probably the battery. That’s the story we’ve been getting from service managers across the country who report that there’s a 90 percent chance an outboard that won’t start has an issue related to fuel or the battery. Boat owners are becoming more aware of ways to prevent the trouble ethanol-blend gasoline can cause a marine engine, but it seems the battery is frequently neglected, perhaps because most of us never need to get under the hood of our very reliable road vehicles these days. We take the battery for granted, until that lack of vigilance ruins a fine Saturday on the water. So find your boat battery and give it some love, as per the instructions of a Yamaha Marine pro we spoke with at the Miami International Boat Show.


Basic Boat Battery Inspection

Get in the habit of periodically checking all batteries on board to make sure they remain secured. On most recreational boats the battery with be placed on a tray and secured with a strap and buckle that goes through the tray and over the battery. Make sure that strap is nice and tight. You don’t want the battery bouncing around in the bilge, and excessive vibration can lead to premature battery failure. I’ve seen some battery strap set-ups that might meet some minimum standard but frankly look pretty cheesy. I prefer an aluminum battery box like the models made by Hardin Marine, which are approved for competition boats, which clamp the battery between a base bracket and a top frame of aluminum alloy.

You’ll also want to check the security of the battery terminal connections, which can loosen in the rough-and-tumble, wake-bashing life of a boat. Just grip the red and black battery cables and wiggle them near the terminal. They should not budge. A loose cable could be the only reason your outboard won’t start, or can’t keep the battery charged. There may be a few other power leads clamped under the terminal bolts. I like to use stainless-steel Nyloc nuts, which have a nylon locking collar inserted within the nut, on the battery terminals. They will stay tight forever. The other ends of those battery cables are connected to your outboard, and it’s a good idea to check the security of those terminals, too, when the cowl’s off.

Battery Maintenance

Most of us don’t get to use our boat every day, and many boats sit idle for weeks between outings. If your boat has a battery switch, turn it off to disconnect the batteries from boat systems that could drain the battery over time–like a radio you accidentally left turned on. On-board battery chargers, a common feature on trailerable fishing boats, are a smart option or accessory to select for runabouts and other family boats that are idle for long periods, as long as there’s power handy where the boat is parked. A battery that’s allowed stay discharged will have a short life, and could be dead when you get back to the cottage. When you inspect the battery during the season, watch for corrosion that can collect around the terminals. Yamaha dealers sell Yamalube Battery Terminal Cleaner & Protector, a spray product that removes moderate corrosion and after a rinse with water leaves behind a protective coating to inhibit further corrosion.

A battery switch, like this one made by Blue Seas Systems, will help ensure your boat battery is alive and healthy when you arrive at the marina.

A battery switch, like this one made by Blue Seas Systems, will help ensure your boat battery is alive and healthy when you arrive at the marina.

If you live in an area that sees very cold temperatures in the winter, remove boat batteries for winter storage so you can keep them in a moderately warm area like a garage or basement, connected to a maintenance battery charger. Clean the battery off after removing it from the boat, check the water level (unless it’s a sealed battery) and top off with distilled water if necessary. I’ve had good luck with Deltran Battery Tender products, which maintain a proper storage voltage during the off-season. Over-charging is as bad for a battery as letting it sit discharged.

If your marine batteries are on their fourth season you are likely on borrowed time. It’s better to replace an aging battery before next season than it is to have it give up the ghost on the weekend—with the entire family standing on the dock as you turn the key and hear very disappointing… silence.

Written by: Charles Plueddeman
Charles Plueddeman is Boats.com's outboard, trailer, and PWC expert. He is a former editor at Boating Magazine and contributor to many national publications since 1986.