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Question for CD 25 owners with a 150 Yamaha

 
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alainP



Joined: 07 Oct 2016
Posts: 86
City/Region: Tucson
State or Province: AZ
C-Dory Year: 2011
C-Dory Model: 25 Cruiser
Vessel Name: deja la
PostPosted: Sun Jun 23, 2019 3:02 pm    Post subject: Question for CD 25 owners with a 150 Yamaha Reply with quote

What prop size and pitch are you using when in full cruising mode (heavily loaded that is) and at sea level? What max rpm do you achieve with that prop? my 15 1/4 x 15 is not to snuff I am thinking of trying a 15.5 x 13.
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thataway



Joined: 02 Nov 2003
Posts: 17792
City/Region: Pensacola
State or Province: FL
C-Dory Year: 2007
C-Dory Model: 25 Cruiser
Vessel Name: thataway
Photos: Thataway
PostPosted: Sun Jun 23, 2019 5:29 pm    Post subject: Reply with quote

What RPM at WOT and what is the WOT speed in statute or nautical MPH? Is the boat heavy or light loaded? Is your prop aluminum or SS, much cup, or none?

If you ever run your boat at higher altitude you will want the lower pitch--or even lower. than 13".

_________________
Bob Austin
Thataway
Thataway (Ex Seaweed) 2007 25 C Dory May 2018
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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alainP



Joined: 07 Oct 2016
Posts: 86
City/Region: Tucson
State or Province: AZ
C-Dory Year: 2011
C-Dory Model: 25 Cruiser
Vessel Name: deja la
PostPosted: Sun Jun 23, 2019 8:33 pm    Post subject: Reply with quote

The boat is mostly heavily loaded, aluminum prop, 0n a good day I'll get to 5k @ WOT playing around with tabs and motor trim. I usually reach high teens in knots then. This is all at sea level when sea conditions allow, hard to find a day with really flat water though, I am sure That makes a difference. As for the amount of cup, it looks like there might be some, I really don't know what constitute a lot or a little in that domain. I always seem to be stern heavy even with 150 fr of chain in the locker, I do have Permatrim on the Yamaha. How many rpm could I expect to gain going to a 13 inch pitch?
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thataway



Joined: 02 Nov 2003
Posts: 17792
City/Region: Pensacola
State or Province: FL
C-Dory Year: 2007
C-Dory Model: 25 Cruiser
Vessel Name: thataway
Photos: Thataway
PostPosted: Mon Jun 24, 2019 10:20 pm    Post subject: Reply with quote

The rule of thumb is that you get 200 to 300 RPM per 2" crop in pitch. But @ cup can make 100 RPM. SS will run better than Aluminums with less "flex".

You are at the low end of RPM for that motor. I would definitely drop to a 13". Is the Permatrim right on the surface of the water? That is where it belongs. If it is buried, then the engine may need to come up a hole or two....Too deep, will slow down.

For example, with a Honda 150, and 15" prop pitch, I get about 5000 and in the 20 mph range when fully loaded for a long cruise. As I use water, fuel, etc, even with the same gear, I can get up to 5500 and 25 mph. When the boat is light, I get 6000 RPM, and 29.7 mph...depending.....So, do I prop for the heaviest load, or for the average. I choose the "middle".
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alainP



Joined: 07 Oct 2016
Posts: 86
City/Region: Tucson
State or Province: AZ
C-Dory Year: 2011
C-Dory Model: 25 Cruiser
Vessel Name: deja la
PostPosted: Thu Jun 27, 2019 10:31 am    Post subject: Reply with quote

I got the 13" yesterday, blades look a little flatter than the 15", we'll see what happens when back in the water. Thanks
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colbysmith



Joined: 02 Oct 2011
Posts: 2864
City/Region: Madison
State or Province: WI
C-Dory Year: 2009
C-Dory Model: 25 Cruiser
Vessel Name: C-Traveler
Photos: C-Traveler and Midnight-Flyer
PostPosted: Thu May 21, 2020 10:23 pm    Post subject: Reply with quote

Alain, what did you find out going to the 13 pitch? I've got the Yamaha 150 on my new to me CD 25. Running it wide open today, I came up with about 32 mph, but at 5200 rpm. I'm probably going to order a new aluminum 15.25 x 13. Colby
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alainP



Joined: 07 Oct 2016
Posts: 86
City/Region: Tucson
State or Province: AZ
C-Dory Year: 2011
C-Dory Model: 25 Cruiser
Vessel Name: deja la
PostPosted: Fri May 22, 2020 11:12 am    Post subject: Reply with quote

Colby, I found out two things, the gain in rpm at WOT seemed very modest but the noise it produced at low rpms was very annoying, The noise was like a rattling can full of gravel and would disappear at around 1900 rpm. i do too much displacement speed while cruising and fishing to put up with that, I went back to the 15 inch pitch and kept the 13 as spare. The prop was a basic Solas aluminum.
I always have a lot of weight up front, in the back and really everywhere. Finding a truly calm day in the Sea with flat waters, no wind or currents for testing props and rpms is rare, especially in the Winter or Spring. so..I gave up on further testing for now, too many other things to fuss with.
32 mph at 5200 rpm is pretty good, you must have been light?
Alain
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colbysmith



Joined: 02 Oct 2011
Posts: 2864
City/Region: Madison
State or Province: WI
C-Dory Year: 2009
C-Dory Model: 25 Cruiser
Vessel Name: C-Traveler
Photos: C-Traveler and Midnight-Flyer
PostPosted: Fri May 22, 2020 10:13 pm    Post subject: Reply with quote

Had full tanks of fuel and water. But that was pretty much it. I'm still setting up the new boat to me. Colby
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