3 blade prop

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deepdive's picture
deepdive
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Posts: 26
3 blade prop

I have a 1983 MKI..engine has been upgraded to a 25XPB by PO. I am going to replace transmission with a ZF 10. Also would like to up from my existing 15x10 two blade to a three blade. Catalina direct showes 15x9, 10 and 12 for our boast..I would appreciate any sage advice from other who have maybe traveled this path...thanks

David Edwards
Bridgeton, NC
C36 MK I hull # 11
S/V Starting Over

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GaryB
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[url]http://www.c36ia.com/forums/showthread.php?t=970&highlight=prop+gary+bai...

Here is a post from a couple of years ago I started with many comments and opinions, enough to keep you busy and probably confused. It sure did me. The final post is the summation of my experience and I am completely pleased with the resultss plus I saved some money with my patience.....Good Luck!

Gary Bain
S/V "Gone With The Wind"
Catalina 36', Hull #: 1056, Year: 1990, Engine: M-35
Standard Rig
Moored: Boothbay Harbor, Maine
Home: Auburn, Maine

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deepdive
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thanks Gary, Just the info i needed, I was wondering the difference the Campbell would make with the cupped blades.

David Edwards
Bridgeton, NC
C36 MK I hull # 11
S/V Starting Over

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deising
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I read the last few posts in that previous thread and have two comments about something that was written: "...showing 6.9 knots which is a bit over Hull Speed, so I am assuming the KM (knot meter) to be off some..."

1. With a waterline close to 30 feet, the hull speed on our C36 boats should be closer to 7.4 knots.

2. Boats can exceed hull speed; it is not an absolute limit. Your hull will probably squat quite a bit and the handling will be funny, but it can do it.

That doesn't help you choose a prop, but I had to correct that misunderstanding.

Good luck!

Duane Ising - Past Commodore (2011-2012)
s/v Diva Di
1999 Catalina 36 Hull #1777
Std rig; wing keel, M35B, Delta (45#)
Punta Gorda, FL
http://www.sailblogs.com/member/diva-di/

Maine Sail
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Posts: 324

You guys might also be interested in reading these posts:

[B][URL="http://forums.sbo.sailboatowners.com/showthread.php?t=140954"]Folding Prop Report[/URL][/B]

[B][URL="http://forums.sbo.sailboatowners.com/showthread.php?t=141820"]Folding Prop Is Gone[/URL][/B]

-Maine Sail
https://www.marinehowto.com/

 

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GaryB
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Posts: 570

[I]We ran at 3000 for almost 10 Minutes and the gauge did read about 190 degrees but the speed was showing 6.9 knots which is a bit over Hull Speed so I am assuming the KM to be off some.[/I]Sorry about that Theoretical hull speed would be about 7.4 knots, must of been a stray thought.

Gary Bain
S/V "Gone With The Wind"
Catalina 36', Hull #: 1056, Year: 1990, Engine: M-35
Standard Rig
Moored: Boothbay Harbor, Maine
Home: Auburn, Maine

caprice 1050
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Posts: 345

The way it was explaned to me by a marine engineer is hull speed has nothing to do with how fast a sailboat can go. After the hull speed is achived the sailboat will sit deeper in the water. The faster a sailboat goes above hull speed it will sink deeper in the water. If we can get a sailboat to go fast enough it can actually be sunk, but to get enough speed it would take an awful lot of power. This is true for all displacement boats. Plainning boats are just the opposite.

__/)__/)__/)__Capt Mike__/)__/)__/)__
Punta Gorda Florida
1990 Std WK M35 Hull #1050

caprice 1050
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Posts: 345

Gary
Are you only using you Knot Meter to determine you speed? Our two boats are only six hull numbers apart. My knot meter compaired to the "Speed Over Ground" reading on my chartplotter was always different regardless if I was going with the tide or aginst it. I pulled the K/M out and left it out now I don't have to pull and clean it almost every time I go out.

Also, I checked my engine RPM's with a digital RPM meter and found a substantial difference in the RPM given by the gage and the meter.

__/)__/)__/)__Capt Mike__/)__/)__/)__
Punta Gorda Florida
1990 Std WK M35 Hull #1050

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GaryB
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Posts: 570

Mike,
I use the KM for relative speed most of the time. I reset the tach several years ago with the correct dip swich settings, but I never have checked the Tach with a timing light on the engine. For the most part in comparing the KM speed to the GPS they are similar in taking into account current. Assuming that my tach is pretty close I have found that at the highest RPM I have the tendancy to run hot. Since installing the 3 blade prop though I have found that the boat moves at a higher speed for any RPM.

Gary Bain
S/V "Gone With The Wind"
Catalina 36', Hull #: 1056, Year: 1990, Engine: M-35
Standard Rig
Moored: Boothbay Harbor, Maine
Home: Auburn, Maine

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