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Prop size for TomCat

 
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squidslayer



Joined: 02 Jul 2005
Posts: 131
City/Region: El Sobrante
State or Province: CA
C-Dory Year: 2007
C-Dory Model: 255 Tomcat
Vessel Name: ShirleyMae
Photos: Shirley Mae
PostPosted: Thu Feb 03, 2011 2:32 am    Post subject: Prop size for TomCat Reply with quote

I got Honda 150's on my Tom Cat with S 3X15X19L Stainless Steel Props
I would like to get more torque in the low RPM's Out here off SF the swells can get BIG and if I happen to be out in them I would like to get a little more hill climbing power. Are their any other TC owners Honda 150's that run different props than what I have? I was thinking of going to a 3X 15X 17 prop
What would be the trade off in performance?
Any input who be appreciated.

DickE
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Discovery



Joined: 08 Dec 2003
Posts: 1239
City/Region: LOA, UTAH
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C-Dory Year: 2006
C-Dory Model: 255 Tomcat
Vessel Name: Discovery
Photos: Discovery
PostPosted: Thu Feb 03, 2011 8:27 am    Post subject: Reply with quote

We are using 3 blade stainless 13 X 17 Honda props on the Honda 135 HP. I am satisfied, but have not tried anything different.

Brent

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Wefings
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Joined: 29 Nov 2005
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PostPosted: Thu Feb 03, 2011 11:37 am    Post subject: Reply with quote

Dick , the 17s will make a big difference for hole shot and acceleration . Those hondas dont make their power till the V tec kicks in at about 4400 RPMs . Just dont run them over 6k and you will be fine .
Marc

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journey on



Joined: 03 Mar 2005
Posts: 3593
City/Region: Valley Centre
State or Province: CA
C-Dory Year: 2005
C-Dory Model: 25 Cruiser
Vessel Name: journey on
Photos: Journey On
PostPosted: Thu Feb 03, 2011 12:25 pm    Post subject: Reply with quote

Just for contrast, we have a Honda 150 on Journey On, a monohull. At present there is a 15" pitch propeller on the engine. When I change to a 16" pitch, there is a noticeable effect on the engine in that it revs slower. You're running 19" pitch on a catamaran (with 2 engines) so obviously you need far less thrust at the lower speeds and are saving the power for when you're going fast. Much faster that I go on Journey On.

Boris
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thataway



Joined: 02 Nov 2003
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City/Region: Pensacola
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Vessel Name: thataway
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PostPosted: Thu Feb 03, 2011 3:14 pm    Post subject: Reply with quote

The question I would ask is what is your WOT RPM currently, and the speed at WOT. Most likely you will do better with the 17's.
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Thataway
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squidslayer



Joined: 02 Jul 2005
Posts: 131
City/Region: El Sobrante
State or Province: CA
C-Dory Year: 2007
C-Dory Model: 255 Tomcat
Vessel Name: ShirleyMae
Photos: Shirley Mae
PostPosted: Thu Feb 03, 2011 11:33 pm    Post subject: Reply with quote

Wide open with the 3X 19s the highest rpm I believe I can go is about 5400rpms@ 37 mph
I think I am going to put on Some Honda 4 blade 17s aluminums for a trial run. The shop says that 4 blades will help also with low rpm torque

Thanks
DickE

quote="thataway"]The question I would ask is what is your WOT RPM currently, and the speed at WOT. Most likely you will do better with the 17's.[/quote]
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Doryman



Joined: 03 Oct 2006
Posts: 3807
City/Region: Anacortes
State or Province: WA
C-Dory Year: 2006
C-Dory Model: 255 Tomcat
Vessel Name: Lori Ann
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PostPosted: Fri Feb 04, 2011 1:07 pm    Post subject: Reply with quote

Marc, Matt -- I want to buy a set of backup props for my cruise this summer. Probably aluminum, possibly the Piranha that I believe Roger uses on Dreamer. What size should I get for my 150 Yamahas and do they make counter-rotating versions? Would they be the same size as what folks use on 150 Hondas?

Thanks,
Warren

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Wefings
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Joined: 29 Nov 2005
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PostPosted: Fri Feb 04, 2011 4:22 pm    Post subject: Reply with quote

Warren, You probably have 19s on the boat now as I remember . I would go with aluminums as spares and you can get them as counter rotators . When I was on your boat it performed very well and I would stick with that pitch . I am not a fan of plastic props except on movie sets, sushi bars and in window box fans .
Marc
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thataway



Joined: 02 Nov 2003
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PostPosted: Fri Feb 04, 2011 4:22 pm    Post subject: Reply with quote

If you have SS props on now, the Aluminum props will flex more, and the sized down will seem to be more than the 2". Also generally the 4 blade prop will give more stern lift, and a slightly lower planing speed. Four blades may not necessarilly give you more low end performance. There are many factors in prop design, including cup, rake as well as pitch and diameter. Some times it is trial and error. It will be interesting to see what the RPM and speed does. If you can deal with a place which will loan the props until you have it dialed in correctly.

The Suzuki outboards have a different gearing, and use a much higher pitch prop--plus a slightly larger diameter--and most of us get a higher speed out of the boats.
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Doryman



Joined: 03 Oct 2006
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City/Region: Anacortes
State or Province: WA
C-Dory Year: 2006
C-Dory Model: 255 Tomcat
Vessel Name: Lori Ann
Photos: Lori Ann
PostPosted: Fri Feb 04, 2011 7:28 pm    Post subject: Reply with quote

Wefings wrote:
Warren, You probably have 19s on the boat now as I remember . I would go with aluminums as spares and you can get them as counter rotators


Marc -- Thanks for that info. I was hoping someone could also tell me what the "usual" pitch is for 19" props, for my engine, so I know what to order.

thataway wrote:
If you have SS props on now, the Aluminum props will flex more, and the sized down will seem to be more than the 2". Also generally the 4 blade prop will give more stern lift, and a slightly lower planing speed. Four blades may not necessarilly give you more low end performance. There are many factors in prop design, including cup, rake as well as pitch and diameter. Some times it is trial and error. It will be interesting to see what the RPM and speed does. If you can deal with a place which will loan the props until you have it dialed in correctly.


Bob -- I am not looking to change the performance of the boat. As Marc says, it is running well with the SS props. I just want to take a spare pair to Alaska with me, and am trying to find out what I should order.

Warren
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squidslayer



Joined: 02 Jul 2005
Posts: 131
City/Region: El Sobrante
State or Province: CA
C-Dory Year: 2007
C-Dory Model: 255 Tomcat
Vessel Name: ShirleyMae
Photos: Shirley Mae
PostPosted: Sat Feb 05, 2011 10:35 am    Post subject: Reply with quote

Bob& Marc

You said that we Alum 4 blade17's "the sized down will seem to be more than the 2".

Do you mean the the alum 17's will actually perform like 15's??
my dealer is willing to let me try them out
Talked to a gent yesterday that has twin hondas on his heavy Cat...he told me he likes the big seas performance of 15's on his cat best
Do you think 15's are to low??
thanks

DickE


thataway wrote:
If you have SS props on now, the Aluminum props will flex more, and the sized down will seem to be more than the 2". Also generally the 4 blade prop will give more stern lift, and a slightly lower planing speed. Four blades may not necessarilly give you more low end performance. There are many factors in prop design, including cup, rake as well as pitch and diameter. Some times it is trial and error. It will be interesting to see what the RPM and speed does. If you can deal with a place which will loan the props until you have it dialed in correctly.

The Suzuki outboards have a different gearing, and use a much higher pitch prop--plus a slightly larger diameter--and most of us get a higher speed out of the boats.
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thataway



Joined: 02 Nov 2003
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City/Region: Pensacola
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Photos: Thataway
PostPosted: Sat Feb 05, 2011 3:50 pm    Post subject: Reply with quote

DickE; I don't think you can predict what the performance will be until you try those specific props. I would try the 4 blade 17's and see how they work. I don't think they will be exactly like 15" SS props. But you may get a few more hundred RPM than you expected--which would be fine, as long as you don't exceed redline. I have run more aluminum props on outboards than SS props. It just happens that currently I have SS props on both of my boats.

Warren; The aluminum are great as back up props--and what I always carry. With any luck you will have no problem at all, but it always is a good idea to carry a spare set of props, with extra pins, cotter keys, thrust washer and prop nut etc.
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