Stay with the 23. RPMs will not change (no more than 50 rpms anyway).
You are already over rated rpms (4800) so going to a 21 is going to be way
to small.
If you get a good performance SS like the Laser II the SS will help
tremendously w/ this problem. A standard black SS will have little to no
effect.

--
Tony
My boats and autos - http://t.thomas.home.mchsi.com



"Jay" wrote in message
m...
Greetings,

Have a '97 Chap 2500lb / 4.3 Mercruiser engine. Run 4900 WOT trimmed
up and that is where porpoising starts. I would like to replace the
alum 23' with a SS. Do I drop to a 21' SS or stay w/ 23'? Have heard
both.

Thanks in advance,
-Jay.