Modern outboard motors are pretty darn reliable. Give them good fuel and a good spark, and there’s very little that is likely to go wrong, assuming you keep the propeller off the bottom. Service experts I’ve talked to over the past few seasons agree that, with the advent in the past decade of computer-controlled, emissions compliant fuel-injected four-stroke and direct-injected two-stroke motors, the two most-likely sources of outboard trouble relate to fuel and the battery. Here are five tips for keeping a good-running outboard going strong this season.

Keep your 250ss Teamblazer and its Suzuki, Honda, Mercury—you name it—running all summer.

Keep your Suzuki 250SS, Honda, Mercury, Yamaha—you name it—running strong all summer.(Picture shows the transom of a Blazer bass boat.)

1. Maintain your fuel: Field service reps tell me that in many parts of the country gasoline can begin to oxidize in just two weeks. Which means that a boat left unused at the cabin for a couple of weekends could have gummed-up carburetors when you return. Follow this protocol when fueling your outboard-powered boat: To get the freshest gas, buy it from a station or gas dock that is busy. When possible avoid gasoline blended with ethanol. Unless you plan to use up the fuel in a few days, add a fuel stabilizer product like Seafoam, Stabil, or an OEM stabilizer to every tank of gas. If the boat will be sitting for a extended period (more than a few weeks) add fresh stabilized gas, and fill the tank to prevent the collection of condensation in the fuel. Click here to learn more about fuel-related issues.

2. Filter your fuel: Your outboard probably has its own, small fuel filter, but consider installing a separate fuel filter between the motor and the tank, especially if you can’t avoid ethanol-blend fuels. A filter with a replaceable element traps water and the gunk that ethanol may be rinsing out of the fuel-delivery chain. You want 10-micron filtration, sized for your engine’s fuel-pumping capacity. Here’s how to install your own filter

Ethanol fuel and outboard motors can be a bad combination. Avoid E-blended fuels when possible; use an extra filter if you can't.

Ethanol fuel and outboard motors can be a bad combination. Avoid E-blended fuels when possible; use an extra filter if you can't.

3.  Baby the battery: If your battery is more than a few seasons old, and you don’t store it with a maintenance charger in the off-season, consider replacing it a new one this year. Periodically check the battery cable connections to make sure they are clean and tight, and check that the battery is mounted in a box or bracket that will keep it secure in the boat. If your boat has a battery switch, turn it off after each outing to prevent accidental drain on the batteries. If the boat will sit unused for an extended period and you have access to power, keep the battery fully charged with a maintenance charger like a Battery Tender.

4.  Check the prop: Dings and nicks in the prop blades will diminish performance and should be repaired by a competent prop shop, but a bent blade will throw the prop out of balance and could lead to very costly trouble. On smaller motors with tiller or cable steering, you are likely to feel a bent blade as a new vibration in the tiller or steering wheel when underway, just as you’d feel a wheel out of balance on your car. But the hydraulic and power steering systems found on many newer, larger boats effectively mask this vibration. Left unchecked, an out-of balance prop causes the prop shaft to wobble, which can lead to gear set failure or cause the propshaft seal to leak, which will also ruin the gears and bearings. You can give your blades an eye-ball check by putting the motor in neutral (please also remove the kill switch) and spinning the prop while the boat is on a trailer or rack. Remember that if you make contact with a soft bottom, you can bend the blades without roughing up the edges. If you are suspicious, have the prop checked at a prop shop.

5.  Shaft and seals: Last season a shop tech in Wisconsin told me that he finds fishing line wrapped on an outboard prop shaft at least once a week. The line accumulates between the prop and the prop shaft seal, and the thrust of the propeller can force the line into the seal, causing it to fail. This allows water into the gearcase, which can destroy the gears and bearings in the time it takes you to run across the lake, leaving you with a repair bill well into four figures. With a little practice, you can pull your prop and inspect the shaft for fish line in about 15 minutes. It’s cheap insurance. We showed you how in a previous article. One other thing: please stop throwing old fish line overboard.

Fishing line wrapped around the prop shaft can damage the shaft seal and lead to gearcase failure.

Fishing line wrapped around the prop shaft can damage the shaft seal and lead to gearcase failure.

Bonus Tip: Never, ever, ever start an outboard motor out of the water unless it is connected to a garden hose flushing device. Just a few seconds of dry operation will ruin the rubber-composite water pump impeller, leading to an overheated motor and all kinds of expensive trouble and inconvenience.

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