Re: omc 1979 stern drive
Grease both trunions (remove the bumpers on either side of the drive, zerks under the bumpers). Grease steering (assuming you have Tru-Course) zerks just under the gear to the starboard side of the ball gear on the intermediate housing (there's another zerks inside the boat on where the steering cable attaches to the intermediate housing as well).
As for oil, there's a fill plug at the bottom of the bullet holding the prop shaft on the lower gear case - the lower lube level check is just below the cavitation plate - both on the starboard side. The upper gear case has a fill plug just above the cavitation plate & level check dipstick in the top cap of the drive (near the 'OMC' emblem). Intermediate has a fill plug on the starboard side below the ball gears & a check near the boot where the upper gear case meets the intermediate.
Good luck - hopefully that all makes sense

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