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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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

--

If you are just "looking" for information a great book written by Dave Gerr
is directed towards answering your question. It is called "The Propeller
Handbook". Lots of pics, charts and diagrams. Hope this helps.
regards,
Mike Brannon


"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

--
Ce message électronique et tous les fichiers attachés qu'il contient sont
confidentiels et destinés exclusivement à l'usage de la personne à
laquelle
ils sont adressés. Si vous avez reçu ce message par erreur, merci de le
retourner à son émetteur. Les idées et opinions présentées dans ce message
sont celles de son auteur, et ne représentent pas nécessairement celles d'
Aqua Services ou d'une quelconque de ses filiales. La publication,
l'usage,
la distribution, l'impression ou la copie non autorisée de ce message et
des
attachements qu'il contient sont strictement interdits.

This e-mail and any files transmitted with it are confidential and
intended
solely for the use of the individual to whom it is addressed. If you have
received this email in error please send it back to the person that sent
it
to you. Any views or opinions presented are solely those of its author and
do
not necessarily represent those of Aqua Services or any of its subsidiary
companies. Unauthorized publication, use, disse

Propcalc by Surfbaud is a free xls spreadhseet that does a pretty fair
job of selecting prop sizes. You enter HP, RPM, gearing, displacement,
LWL and a couple of other variables. By playing around with the
variables you can get a pretty good idea of what various effects will
be. I found it at http://www.yosc.bctalk.net/navsoft.htm

Castle Marine has another free calculator on their site
http://www.castlemarine.co.uk/pitch.htm
It is a windoze app and a bit more polished than the Surfbaud
spreadsheet and more oriented to powerboats than sail but it gives the
same results.


Sylvain Sirois wrote:
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


--
Glenn Ashmore

I'm building a 45' cutter in strip/composite. Watch my progress (or lack
there of) at: http://www.rutuonline.com
Shameless Commercial Division: http://www.spade-anchor-us.com