One consideration here is the gearing between the prop and the engine. You may
have to increase that to match the prop better. For a heavy displacement hull,
you
want a slower turning prop with lot's of torque. If your current prop is
churning up
a lot of turbulence, increasing the prop surface area by adding a blade may
smoothen
things out. Not sure this is helpful, but I push my Westerly 22 with a Yamaha
outboard which has 3 blades and is toted as a 'pusher', mainly because of the
prop
and the higher gear ratio of 3:1. Most outboards have lower gear ratios around
2.5
or less. The best pusher I ever had was a British Seagull with a 4:1 gear ratio
and
a six bladed prop.

Sherwin D.

terry wrote:

Thinking of changing to a 3 blade prop?
Westerly 26 foot about 7000 pounds when in the water and occupied.
Engine is a Volvo MD1B (9 HP) with maximum speed of 1800 RPM via a 1:1
forward reverse gear.
Reason for change is we need a new prop.
Also advice some years back from a couple who took a similar size boat
cruising the Caribbean and claimed that the 3 blade was much better,
while experiencing no increased drag under sail!
Would welcome any comments/advice.
Terry