How Often Should You Change Oil

Nov 10, 2022

Clean oil in your boat’s engine or outboard motor is essential to its longevity and performance. The standard interval for changing boat oil is 100 hours. For most boat owners this is once a season. Boats that are run hard should change oil closer to the 50-hour mark. Diesel marine engine oil change interval varies from 50-200 hours depending on the manufacturer. The first change on a brand new motor is generally at 20 hours.

Best Time of Year to Change Boat Oil

The most important period is in the fall before storing your boat for winter. Research suggests that a motor lasts 50% longer by storing it with clean oil. That’s significant! This is because used oil has contaminants and moisture that corrodes the engine internals while it’s not being used.

If your boat is used frequently during the boating season, you may need to change the oil mid season as well. This is especially true if your boat is run hard, or used for towing.

If your boat is run year-round, you’ll need to keep track of the engine hours and oil change date. A good method for all boat owners is to write with a marker on the oil filter the engine hours and date of the oil change service.

What is the Best Type of Boat Oil to Use?

This question is best answered in the owner’s manual for your boat. If you don’t have the owner’s manual, look it up online for your specific boat model.

You will always choose marine grade oil that is designed for the rigor and demands of a boat motor. You should choose oil that meets or exceeds your manufacturer’s recommendation.

Marine oil performs at a higher level than automotive oil. A marine engine is under constant strain and often runs at high rpm’s. Marine oil is corrosion and moisture resistant and also contains anti-oxidants to enhance engine longevity.

You can choose single weight oil like an SAE 30, or multi-viscosity oil like 20W- 40. There will be a viscosity chart in your boat owner’s manual that will recommend what is the proper oil choice depending on the climate in which you operate your boat.

Is Synthetic Oil Better for a Boat Motor?

Generally speaking, synthetic oil is a great choice for a boat motor and has many benefits including low carbon buildup inside your engine. Furthermore, synthetic oil lasts longer between oil change intervals, extends engine life, will make your engine quieter, run smoother, and smoke less.

The biggest drawback of synthetic oil is its cost. Synthetic oil costs twice as much as standard oil, but the benefits likely outweigh the cost difference.

Before using synthetic oil, check your boat owner’s manual.

Required Supplies to Change Boat Oil

1) The right amount of marine motor oil that meets or exceeds the engine manufacturer’s specifications.
2) An OEM oil filter from the marine engine manufacturer or a high performance filter that exceeds specs.
3) An oil filter wrench to remove the old filter.
4) An absorbent Pad
5) A container to hold the used oil
6) A Funnel
7) An extractor pump to remove used oil through the dipstick tube, or a wrench to remove oil drain plug and possibly a kit that contains a fitting and drain hose to drain used engine oil.

How to Change Oil in an Inboard or Outboard Boat Motor

1) Warm up the boat engine to circulate the used oil and to make it easier to drain. Don’t make it too hot where it can burn you.
2) Remove the oil fill cap to vent the engine and make draining easier.
3) For removing old engine oil, most pros use an oil extractor pump that has a small hose to put down the oil dipstick tube and manually pump the used oil out. The extractor pump container has markings that tell how much volume of used oil you’ve removed so you can be certain you’ve removed all of the used oil. If you plan to change your own boat oil for the long term, you should invest in an oil extractor pump, because it keeps things from getting messy. As an alternative, some engines and outboard motors have easy to access oil drain plugs, however, most do not. For a difficult to access drain plug use an oil change kit with a fitting and hose that controls the flow of oil from the drain into your waste container.
4) After draining the engine oil, carefully remove the old oil filter using a filter wrench. Some people like to use an inside out zip lock bag to grasp the filter and capture any spills upon removal. Inspect that the rubber filter gasket came off with the old filter. Clean up any spilled oil with an absorbent pad.

5) Replace the engine oil filter with a new filter that meets or exceeds manufacturer specifications. Apply a coat of oil to the rubber gasket of the new filter and hand-tighten the filter so it’s snug. It’s a good idea to write the date of oil change along with engine hours and oil used on the new filter with a marker.

6) If you removed the oil drain plug, clean the plug and washer. Wipe the drain opening clean before replacing and tightening the plug.

7) Using a funnel, slowly add the recommended volume of new oil to the engine. Replace the cap for the oil fill. Let the oil settle, run the engine for a short while, then check the oil level with the dipstick.

8) Inspect for any oil leaks around the plug and oil filter.
9) Properly dispose of the used motor oil at a local service garage.

Is it Better to Use a Boat Shop to Change Boat Oil?
Do you change your own oil in your car? If the answer is yes, you likely have the confidence and skills to change the oil in your boat.

However, if you don’t change the oil in your car yourself, there are likely good reasons why you don’t.

Reasons to Use a Boat Shop for this Procedure

Peace of mind it’s done correctly by certified marine technicians.

  • For DIY, you’ll need to organize the purchase of the correct marine oil, OEM oil filter, and necessary supplies.
  • For DIY, you need a space to do the work, and if you spill some oil, you don’t want to make a mess that you’ll regret, like a stain on your driveway.
  • For DIY, unless you’re a skilled mechanic, you’ll likely make some level of mess that you’ll have to clean up from your floor, your bilge, or your boat’s carpet.
  • For DIY, you’ll likely need some specialty tools.

For DIY, you’ll be required to dispose of the used oil properly by taking it to a local garage.

If you schedule a boat oil change with Lakeside Marine, you’ll drop your boat off in the morning, and pick it up at the day’s end. Get the lower end or outdrive gear lube changed at the same time. Have a certified mechanic look over the entirety of your boat while it’s there in the shop, and be certain everything is in order so you can enjoy your boating season to it’s fullest.


Changing the oil in your boat’s engine or outboard motor at the end of every season is likely the most important aspect of boat maintenance. Every 100 hours or once a season, whichever comes first is the standard interval.

While changing your boat oil as a DIY project can save you money, there are many compelling reasons to have your boat’s oil changed by professional technicians at a boat shop.

Voted the Best Boat Repair Shop on Lake Lanier we have a proven track record for excellence in all aspects of boat maintenance and marine repairs. Get the performance that you desire from your boat by trusting the professional marine mechanics at Lakeside Marine to do your work correctly the first time. Our expertise saves you both time, and money.

Call and schedule our convenient same day boat oil change at Lakeside Marine (678) 322-7877 or schedule online at



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