Can You Fill Lower Unit Oil from Top? (Guide)

can you fill lower unit oil from top
can you fill lower unit oil from top

The brand and the model of the outboard have a huge impact on the servicing requirements. While the manual covers all serving the care requirements in extensive detail, it also helps to learn from a trained professional. That way, you will minimize the time it takes to service the outboard, and you’ll learn a ton of new techniques to help with managing the performance of your unit. Anglers often seem to be confused when it comes to filling the oil in the lower unit from the top. This gearcase can be pretty hard to manage when you’re adding more oil for the first time, so let’s go through some details on how you can fill lower unit oil from the top.

Can You Fill Lower Unit Oil from Top? 

While it is possible to top off the bottom unit with the help of an additional tube, it is almost always better to stick with the bottom inlet to fill the oil in the lower section. It is next to impossible to avoid the air pockets in the system while using the top hole without any extra gadgets. So, make sure to get a tube or a syringe to fill up the bottom unit from the top.

  • Start by cutting the power to the unit and then using the tilt trim to drain all the oil out of the lower unit. You’ll find an outlet at the starboard side of the boat, and a container should be placed below the outlet to avoid any extra mess.
  • Once the oil has been removed from the unit, you can put the screw back into place and rely on a lube pump to get the oil into the lower unit from the top hole.
  • Make sure to use a small diameter of the tube to get the oil into the lower section of your outboard. Otherwise, you will be dealing with a lot of air pockets, and the oil will start to leak once the unit gets a bit warm.
  • After a few pumps, the oil will start to leak from the top hole, and the tube will get covered with oil. This will indicate the motor has been filled with oil, and you can put the screw back into the top hole to complete the process.
  • Some anglers also prefer to rely on the tilt trim components to readjust the angle of the motor. This removes the extra air pockets from the oil, and you will ultimately get better performance from the outboard.

These steps might seem simple, but you will get far better performance by relying on the bottom hole to fill up the section. Even if you follow these steps perfectly, you will run into problems with the air pockets in the oil compartment.

However, this issue can be avoided by using a reliable oil pump in the lower section of your motor. So, keep that in mind if you’re struggling with filling the oil in the lower unit. The lube pump will only cost a few bucks and will have a substantial impact on the final performance of your unit.

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