Re: 89 nissan outboard 3 stroke egine, needs prop...dont know what i need?
First, you need to tell us what HP your Nissan motor is. There is no such thing as a 3 stroke motor. It's either a 2 stroke or a 4 stroke; in 1989 I'd bet on 2 stroke for Nissan.
You can look up your Nissan motor in the prop section and see what props are available for it. The size (pitch) will depend upon what sort of boat it's on.