Suggested prop size for a 1997 90hp Yamaha autolube 2 stroke

[Rigaud]

As some have clearly mentioned here going from a 15 to 17" pitch means nothing if thier not the exact same prop other then the pitch. I went from a 19 to a 23 pitch but totally different styles of prop just for fun since I don't pay to test out props. Well my top end was exactly the same @ 50mph and within 50 revs of each other. Boat set-up was identical to make certain I was comparing fairly.

Just some food for thought and the problem might be simpler than most think.

[Jeff J]

Both the 17" and the 15" were Yamaha K props if that means anything.

Am i right in thinking that i should get more top end than 24 to 28 mph from this engine though.

Would going up in prop size to 19" or 21" make any difference ?.

[Nos4r2]

Originally Posted by Jeff J

Both the 17" and the 15" were Yamaha K props if that means anything.

Am i right in thinking that i should get more top end than 24 to 28 mph from this engine though.

Would going up in prop size to 19" or 21" make any difference ?.

Both ally? If they were both ally K series props then start investigating other causes.

BTw,you won't turn a 21" properly with a Yam 90 on a boat that big.

[Jeff J]

Ok Nos4r2 thanks for that much appreciated info and yes they were both the k ally props.

Any ideas as to where to go next then guys.

Cheers

[Downhilldai]

Originally Posted by Jeff J

...Any ideas as to where to go next then guys.

To an outboard service workshop.