1986 Merc 75 hp gear oil

[alhntr]

Hi all,

New here. I have purchased a used 1986 Merc 75 hp to re power my old 65 16' Starcraft aluminum V hull. Got it started after carb clean. Now I am ready to change lower unit oil. I see the oil recommended for less than 75hp......what weight is ok for 75 hp 1986 lower case. 85/90 ? Thanks

 

[kavie]

I think its sae 80W-90 or SAE 90 as Mercury lists as the latest one:

Quicksilver 858064Q01 High Performance SAE 90 Gear Lube for Mercury Outboards and MerCruiser Sterndrives. ​

 

[timguy]

Hi, welcome. That is correct what Kavie says. I change gear oil yearly on the boats that we use regularly. Drain and refill for the storage season. That way in the springtime you can see if any leaks have developed in the prop shaft seal, or even in the shift shaft (if applicable) or the input shaft.....if its stored laying down. Remember always insure that your prop cannot spin when towing your boat on its trailer. Why? The outer seal, or outer seal lip, (whichever applies to your shaft seal design), will dry out and melt. This is because when your in the water, that seal is lubricated and kept cool by the water itself. I am very surprised how many boaters don't know this.

 

[alhntr]

Hi, welcome. That is correct what Kavie says. I change gear oil yearly on the boats that we use regularly. Drain and refill for the storage season. That way in the springtime you can see if any leaks have developed in the prop shaft seal, or even in the shift shaft (if applicable) or the input shaft.....if its stored laying down. Remember always insure that your prop cannot spin when towing your boat on its trailer. Why? The outer seal, or outer seal lip, (whichever applies to your shaft seal design), will dry out and melt. This is because when your in the water, that seal is lubricated and kept cool by the water itself. I am very surprised how many boaters don't know this.

Thanks for tip guys.