In addition to regular oil changes, at the 100 & 300 hour mark, a more in-depth inspection and service is recommended on the outboard. We suggest this be done once a year, at minimum. However, if you use your boat year-round, this annual maintenance service checklist should be twice per year.

Here’s what you can expect at the 100 hr service:

1. Change the Engine Oil (4-stroke)

Outboards, just as any engine need oil changes too. Drain the oil from your outboard motor and replace it with new oil. Refer to your outboard manufacturer’s recommendations for what type of oil to use.

2. Change the Lower Unit Oil

Just like the engine oil, the lower unit or gearcase oil needs to be changed out. Drain and replace your outboard’s lower unit gearcase oil, again using the manufacturer’s recommendation for which type of oil to use.

3. Replace the Spark Plugs

A bad spark plug can leave you stranded out on the water, so make sure to change them all out. Spark plugs are a cheap and easy part to replace on your outboard.

4. Replace the Water Pump Impeller

On your outboard motor, water pump impellers are another cheap and easy part to replace. It is recommended that the impeller be changed once a year to help keep your water pump from failing. While replacing the impeller, be sure to check the water pump canister, and the lower plate or housing for wear or damage, and replace them if necessary. 

5. Replace the Thermostat

Thermostats don’t usually need to be replaced every year, but check with your outboard’s owner’s manual for how often the thermostats need to be replaced, and make it part of the annual service if it’s time to change it out. They cannot be serviced, so it should be replaced with a new one and the old one should be discarded.

6. Inspect Propellers

Check the propellers for damage. While minor abrasions and blemishes can be removed with a file, a propeller needs to be replaced if it has any serious dents or deformities on the blades. 

7. Grease the Fittings

Be sure to use marine grease to coat any grease fittings (or zerk fittings) on the trim-and-tilt, as well as steering mechanism.

8. Cooling System

If your outboard runs in salt water, flush the cooling system with a salt remover formula to remove any salt deposits before flushing it with fresh water. Then flush the cooling system for several minutes with fresh water. Salt, sand and silt cause blockages in the engine.

9. Engine Leak-down Test

Doing a leak-down test once a year can help you check if it’s in peak condition. This test is a good indicator of the overall health of an outboard engine.

These items are an important way in which a typical 100 hour & 300 hour service can keep your outboard in peak condition. However, this can change especially if you are considering winterizing your boat as well.

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