Sylvain:

Please consider contacting a professional propeller distributor for a
sizing. They have the ability to properly size both the propeller and gear
ratio, as well as look at all of the other associated issues - selection of
the right number of blades and BAR, proper material type, cavitation levels,
need for cupping, suitability of your existing shafting.

An alternative is to contact a propeller specialist. While our company
provides prop sizing software to most of the inboard dealer/distributors
(some 150 companies to date) - and going to them would be my first
recommendation - we could provide you with an independent sizing/analysis.
The cost for this service is typically about US$500. This may seem like a
lot to pay for a prop sizing and performance analysis, but considering that
a pair of new 24" bronze 3-blade propellers will cost more than US$1800, and
I'm sure the gear boxes are not free, this is cost-effective insurance.

If you are interested in considering our services, you can contact us
through our web site at http://www.hydrocompinc.com.

Regards,

Don

Donald M. MacPherson
VP Technical Director
HydroComp, Inc.



"Sylvain Sirois" wrote in message
...
Hi, first, excuse my english.
I am in the process of buying an old 44' rescue boat.
http://home.online.no/~lawford/xrl/xrl.htm, and restoring it.

It was originaly equiped with detroit diesel, serie 53. ± 200 hp

Cruising speed was 13 kn and top, 16kn.

Now, the engines are twin cummins 220hp at 220 RPM
The gear box are different, one is a twin disk 2.0 to 1.0
The other is a Borg warner 2.5 to 1.0

The prop are 24 x 20 3 blades.

I would like to restore the original performances of the boat, without
changing the engines.

What combination of gear box and prop i need ?

Thank you

Sylvain
Baie-Comeau, Québec

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