How do I change my oil?

[Brylk1830]

I have a 97 4O hp 3 cylin Mercury outboard and i'm wondering how to change the oil?

[tuantom]

I could be wrong; but I'm pretty sure you have a 2-stroke. Therefore - you don't unless you're talking about the gearcase.

[marshmat]

A '97 Merc 40 is most likely a two-stroke.

Engine lubrication in these comes from the TCW2 or TCW3 oil that you are either mixing with the gas or pouring into the oil injector tank every few trips.

Changing the gearcase oil is usually a once-per-year procedure for typical pleasure boats (if you put on a lot of hours, change it mid-season too). Is this what you're talking about?

[Brylk1830]

My engine does have 3 cylinders but in my maintenance and warranty manual it briefly mentions Quicksilver NMMA/BIA Certified TC-W3 2-cycle outboard oil.
It also is of the oil injection type so I don't need to mix oil with the fuel each time. I'm wondering how to drain the oil that's in the oil injection system and replace it?

[marshmat]

It also is of the oil injection type where I do not need to mix oil with the fuel each time. I'm wondering how to drain the oil that's in the oil injection window and replace it?
Generally speaking, you don't. If you accidentally put a bad batch of oil or the wrong kind in there, you can unbolt the tank and remove the pickup hose to drain it. But generally you just keep that tank topped up and the outboard will decide how quickly to burn it off.
You don't have to use Merc's Quicksilver brand. Any marine 2-stroke oil with the TCW3 rating will work. And I'm not aware of any problems with blending different brands in there, so long as they all meet the TCW3 rating.