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Pescador2
Joined: 19 Nov 2016 Posts: 8 City/Region: Duluth
State or Province: MN
C-Dory Year: 2007
C-Dory Model: 255 Tomcat
Vessel Name: Uno Mas
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Posted: Fri Sep 25, 2020 5:11 pm Post subject: Tomcat prop question |
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I have a2007 tomcat with twin Suzuki 150 hp motors counter rotating prop on starboard engine permatrims installed 3x16x21.5 SS props I am generally very satisfied with performance ...3200rpm 21-22 mph. 3800 rpm 27-28 mph 5100-5200rpm 42 mph. Primarily Fresh water use. I am considering going to a 4 blade to achieve a lower plane rpm as well increasing wot rpm to increase wot speed ....I have found a Suzuki Water grip 4x15.25 x22 SS prop.....what can I generally expect going to a 4 blade and is the above 4 blade a good match...other recommendations |
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thataway
Joined: 02 Nov 2003 Posts: 20808 City/Region: Pensacola
State or Province: FL
C-Dory Year: 2007
C-Dory Model: 25 Cruiser
Vessel Name: thataway
Photos: Thataway
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Posted: Fri Sep 25, 2020 7:03 pm Post subject: |
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Is your WOT the 5200 RPM and 42 MPH? We had a 4 blade Power Tech (I believe) and our WOT light boat was almost 50 mph at 6,000 RPM. I am not positive about the pitch, I may have the build sheet and can check. I believe it was 19 or 20 inch pitch.
You need more RPM, and putting on a 4 blade, with more pitch will actually lower you WOT RPM. You are lowering the diameter slightly--My best guess is that you will not get the increase of RPM--but I don't know the cup and rake etc of the "Water Grip" props. A 4 blade does give more stern lift and more low end performnacnce out of the hole, But generally 3 blade props are faster.
You also want the Props to rotate in, which you have. --instead of out as a normal twin screw. The motors have to be set at proper height, so you just see the top of the antiventiallation plate when on a good plane.
I found that Permatrims didn't really help the plane at lower speed--they thru a lot of water, and were almost counter productive. I had put them on attempting to get a lower planing speed. _________________ Bob Austin
Thataway
Thataway (Ex Seaweed) 2007 25 C Dory May 2018 to Oct. 2021
Thisaway 2006 22' CDory November 2011 to May 2018
Caracal 18 140 Suzuki 2007 to present
Thataway TomCat 255 150 Suzukis June 2006 thru August 2011
C Pelican; 1992, 22 Cruiser, 2002 thru 2006
Frequent Sea; 2003 C D 25, 2007 thru 2009
KA6PKB
Home port: Pensacola FL |
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Pescador2
Joined: 19 Nov 2016 Posts: 8 City/Region: Duluth
State or Province: MN
C-Dory Year: 2007
C-Dory Model: 255 Tomcat
Vessel Name: Uno Mas
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Posted: Fri Sep 25, 2020 8:39 pm Post subject: |
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Yes 5200rpm 42mph medium weight in boat. Motors trimmed up Antiventiallation plate at water level on plane I did notice more stern lift with permatrims water rises up on motors a bit more a lower speeds And they throw more water. I cruise mainly on Lake Superior with short wave sets so I’m mostly attempting to keep on plane at lower rpms I do understand that 3 blades are faster not a big issue as I Seldom cruise at wot ...however it’s still puzzling why I can’t get over 5200 rpms At wot? Ideas? Sounds like your 4 blades Are what I need. Thanks for your response Joe |
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