Change Lower Unit Oil Suzuki Outboard DF 70 80 90 115 HP

Lower unit gearcase oil is a lubricant derived from petroleum and made specifically to protect a Suzuki outboard lower unit gear case. The gear oil is made of a higher viscosity to adequately protect the gears.

Changing lower unit gearcase oil is critical for outboard reliability and proper operation. If the lower unit oil is not replaced on a regular basis, the lower unit can quickly become contaminated with water or run low on oil. Water contamination is the most common cause of lower unit failure. Water often enters the lower unit when fishing line or other foreign objects become entangled around the propeller shaft, and subsequently, damage the seal.

Gear Oil Change


It’s important to change gear oil on the Suzuki outboard every 100 hours of use (or 6 months). Follow these instructions and learn how to change the lower unit oil on a Suzuki outboard 70 hp, 80 hp or 90 hp engine.

  1. Position the Suzuki outboard motor perfectly upright and on a level surface.
  2. Position a suitable container underneath the lower unit.
  3. Remove lower unit gear oil drain plug first (located on the bottom of lower unit). Then take off the gear oil level plug and allow the gear oil to drain.
  4. Swap in new gear oil though oil drain hole. Only use recommended gear oil (Suzuki Outboard Motor Gear Oil or API classification GL5, Viscosity rating SAE # 90 Hypoid gear oil.) Fill the gear case until oil begins to flow out from the oil level hole (gear oil amounts: 28.7/30.0 US/Imp. oz or 850 ml 2009 thru 2011 models, and 1050 ml (35.5 / 37.0 US / Imp. oz for 2001 thru 2008 models).
  5. You will need to reinstall the oil level plug before you remove the oil filter tube from the outboard’s drain hole.
  6. Reinstall oil drain plug.

How to Change the Lower Unit Oil on a Boat

Never reuse gaskets once removed. Always use a new original equipment manufacturer part. To avoid premature lower unit failure. Recheck gear oil 10 minutes after replacing to allow for settling. If the outboard oil level is low, add more gear oil until its level is correct.

Personally, I’d recommended you inspect the lower unit oil before and after each use for signs of leaking oil. And check the lower unit oil level monthly by removing the unit level plug and performing an inspection. Lastly, never perform service or repair to your outboard without a factory repair manual present.

The change gear oil instructions provided specifically pertain to 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 Suzuki four-stroke, 4-stroke DF70, DF80, DF90, DF115, DF140 outboards (70, 80, 90,, 115, 140 horsepower).

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