650 merc prop question

Yachtzee

Seaman
Joined
Oct 13, 2007
Messages
72
I have a 16 ft semi V aluminum runabout with a 1969 650 merc.
Prop is mercury 3 blade 13 3/4 X 15 I can get 28 mph wot. 3 people 10 gal gas.

Tach is brand new but a bit goofy, It shows 4000 at wot but it sounds a bit higher then the tach will peg from time to time.

Do you think a bit less prop could get a bit more top speed (if the tach is right one would think?) or should I leave well enough alone? I just spent $ to come down from 13 3/4 X 17 to 13 3/4 x 15
picked up almost 8 mph.

I'd be thankful for any advice and opinions
 
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