How often to change gear oil?

[JohnWI]

New to me 1984 70HP Evinrude.

PO said it was last changed about 2 seasons ago and didn't use the boat "that often." OK...so that means about 50 hours per year or so in my mind.

Other than through the screws, I'm assuming there are other seals that keep water from intruding, correct? What do you guys suggest I keep an eye on?

 

[andrewddrennon]

Re: How often to change gear oil?

check the gear lube by cracking the bottom drain plug. If its black change it, if its milky you have a leaking seal.

 

[Cap'n Chaos]

Re: How often to change gear oil?

Most people change once a year when replacing the impeller, get into a routine and change it at the end of the season or beginning... could you run longer than that without changing either, sure you could.

 

[wired247]

Re: How often to change gear oil?

Most people? Most people change their oil and impeller NEVER or do so when they start overheating.

I know for a fact the impeller in my 1981 lower has been changed twice in 31 years..

 

[Cap'n Chaos]

Re: How often to change gear oil?

Well then call me odd, I also change the oil in my vehicles every 3 months or 3000 miles... I'll keep an eye out for your rebuild thread.

 

[mark1961]

Re: How often to change gear oil?

From the manufacturer......

"Drain and refill every 100 hours of operation or once each season, whichever occurs first."

In other words......its overdue.

 

[emdsapmgr]

Re: How often to change gear oil?

Another reason to change the oil annually: Most folks change their gear oil when the engine is winterized. If the lower unit suffers a seal failure during summer operation-water can enter the gear drive casing. If the engine is stored in freezing temps over the winter, the water/oil mix in the drive can freeze and burst the casing, a huge expense. If you change the oil each fall, you can see if you have water intrustion by the color of the old lower unit oil when it drains out.

 

[AEROCOOK]

Re: How often to change gear oil?

well then call me odd, i also change the oil in my vehicles every 3 months or 3000 miles... I'll keep an eye out for your rebuild thread. :d

x2

 

[JohnWI]

Re: How often to change gear oil?

Another newbie question...I know I need to replace a thrust washer, also.
If I'm doing that change, is the gear oil going to come gushing out (ie do I need to drain the L U first).

I'm asking as I think I can get some gear lube from walmart (Or do I need OMC lube as they only sell the Merc brand) today and do the change before I can get that washer ordered up online and received.

What seals might be failing to allow the water into the L U? Prop seals or? Is that broken thrust washer going to be indicative of a likely intrusion?

 

[hidef]

Re: How often to change gear oil?

Nothing will come gushing out when you change the thrust washer. All of the seals are in the gear case. Mercury gear case lube is fine as long as it is 85W90.