I bought a used fishing boat last season with a 90-horsepower outboard motor that ran fine, but I want to do a thorough preseason maintenance check myself before taking it out this spring. I'm comfortable changing the lower unit oil and spark plugs, but I'm unsure about the impeller replacement schedule and how to properly inspect the fuel system for ethanol-related issues. For fellow boat owners, what is your essential checklist for annual outboard motor maintenance? How do you test the water pump's effectiveness and what are the signs that the impeller needs immediate replacement, and what fuel stabilizers or additives have you found most effective for preventing problems when the motor sits for a few weeks between uses?
Nice plan. Here's a practical preseason maintenance checklist you can run through in a couple of afternoons.
- Inspect lower unit oil (drain, check color, refill to spec).
- Check gearcase seals and anodes; look for corrosion signs.
- Inspect prop and hub; clean and grease prop shaft; torque to spec on reinstall.
- Spark plugs (you mentioned you’ll do these) and general ignition check if accessible.
- Fuel system: inspect hoses for cracking or hardening, replace with ethanol-safe lines if needed; check primer bulb for cracks; drain old fuel and replace with fresh.
- Impeller and water pump: plan to inspect; update schedule below; clean cooling water intake screen if present.
- Cooling system: flush out any built-up sediment with fresh water; inspect water cooling passages if you can.
- Battery and electrical connections: clean terminals, test charge.
- Fuel filter/water separator: replace if present; check for water in fuel.
- Storage prep: if you’re not using the boat soon, fog or stabilize fuel per manual, and consider winterizing if you’re in a freezing climate.
- Create a simple maintenance log: date, what you did, parts replaced, notes on condition.
If you want, share your engine make/model and whether you’ll be running in salt or fresh water this season and I can tailor a more exact checklist.