Drain gear oil to service water pump? F70

[chartscharts]

Don't have the parts yet for my water pump service, but thought I'd change the gear oil today. But the service manual page 8-3 says to drain the gear oil as the first step of removing the lower unit. If true, I should wait till I have my parts and do the gear oil change when I do the water pump.

But the videos I've seen about water pump service never talk about the gear oil. In which case, I could change my gear oil today, and when I do my water pump later, I wouldn't have to change it again.

Does anyone know if the service manual only says that because it assumes you're going to go further than the water pump in the lower unit?

Do you really need to drain the gear oil to service your water pump?

[robert graham]

The gear oil change and the water pump service aren’t related…..I change my gear oil about once a year at the end of the boating season. Then I check/change water pump about every other year, depending on service.

[99yam40]

just a good idea to know if there is water in the oil, and may need to be resealing the lower while you are changing the water pump

[fairdeal]

Does anyone know if the service manual only says that because it assumes you're going to go further than the water pump in the lower unit?

Yes, that is the way it is written.

Do you really need to drain the gear oil to service your water pump?

No, you do not. The two are independent.

[chartscharts]

Thanks, everyone!

[Keithbaja]

1st thing I do on any outboard or out drive is crack the bottom drain/fill screw and check for water. That determines next procedure. After 45+ yes in the biz, it's standard procedure. If little water, pressure test. Don't drain gear case if lots of water till you have seals on hand to replace. If you drain it then wait for seal%s to arrive. you have invited rust to start inside and not sea it.

[byron.akhavi@gmail.com]

The lower unit is pressure tested to check for seal leakage. The manual notes this and that is why it is noted with the water pump change. 10 PSI of pressure for 10 sec will confirm your lower unit does not have seal leakage. Also, checking the oil and looking for water in it (milky color). That test is why the gear oil needs to be drained. However, it is not required for a water pump change. I change my lower unit in the fall during winterizing. Then check the oil for leaks and pressure test. Then the water pump in the spring to start the season with a new impeller. I know the seals were good before the winterization.

[Keithbaja]

The rules..... Salt water duty 50 HRs change/ck lwr unit gear oil... Fresh water... 100 hrs this well established for many reasons. And pressure test a any/all gearcase's at 14 PSI and turn shafts. Also spin drive shaft and prop shaft during test. Don't forget shiftshaft seal too. Then do vacuum test at 10 kpg vacum while spinning said (3) three shafts. Using windex or soapy water in a spray bottle is OK if unit is going to be used, soon. The guys that build these units lay it SOOO simple in the service manual....