An outboard that is looked after will start first time and run for years. One that is not tends to fail at the worst moment, usually a long way from the slipway. The good news is that most of the routine work is simple. This checklist covers the basics. Always follow the service intervals in your engine's own manual, as they vary by make, size and whether it is a 2-stroke or 4-stroke.
After every trip
- Flush with fresh water if you have been in salt or brackish water. Use flushing muffs or the flushing port, and run the engine (or connect the hose, depending on your model) until the water runs clean.
- Check the tell-tale, the small stream of cooling water. A weak or missing stream while running means a blocked outlet or a tired water pump impeller.
- Rinse the outside of the engine and bracket to remove salt.
- Tilt the engine up when moored or on the trailer, so the leg drains and is out of the water.
Fuel: the most common cause of trouble
Modern petrol absorbs water and goes stale over a few months. That leads to rough running, poor starting and gummed-up carburettors or injectors.
- Fit a water-separating fuel filter between tank and engine, and drain or replace it regularly. Our water-separating fuel filter catches water and debris before they reach the engine.
- Check the fuel line, primer bulb and connectors for cracks or air leaks.
- Use fuel stabiliser if the boat will sit for more than a few weeks.
At the start of the season
- Gear oil. Drain a little from the lower unit. Milky oil means water is getting past a seal and needs attention before it damages the gears.
- Engine oil and filter on 4-stroke engines, at the interval in your manual.
- Spark plugs. Check the gap and condition, and replace if worn or fouled.
- Water pump impeller. Many manufacturers recommend replacing it every one to three seasons. It is cheap compared with an overheated engine.
- Propeller. Look for chips, bends and fishing line wrapped behind it, which can cut the prop shaft seal.
- Anodes. Replace them when around half worn. Never paint them.
- Grease points on the swivel and tilt tubes, and check the steering moves freely.
- Kill cord. Check it is present, undamaged and that the engine stops when it is pulled.
At the end of the season
- Flush thoroughly and let the engine drain upright.
- Treat or run off the fuel, as your manual advises.
- Change the gear oil so the lower unit sits over winter with fresh oil.
- Fog the engine if your manufacturer recommends it.
- Remove the battery and keep it charged somewhere dry.
- Fit a breathable outboard motor cover to keep rain, sun and dust off.
Spares worth keeping on board
- A spare kill cord
- Spark plugs and a plug spanner
- A spare fuel filter element
- Shear pin or propeller nut and split pin, for older engines
- Basic tools, tape and cable ties
Products in this guide
- Water Separating Fuel Filter: removes water and debris before fuel reaches the engine.
- Inline Fuel Filter: replacement inline filter, see the product page for engines it fits.
- Outboard Thermostat Kit: for Mercury outboards.
- Outboard Water Pump Repair Kit: diaphragm and gasket kit for Yamaha 2-stroke outboards.
- Outboard Motor Cover: waterproof Oxford fabric cover for 6 to 15 HP engines.
Check the fit details on each product page, browse all outboard engine parts, or ask us and we will help you find the right part for your engine.