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Raw Water Impellers
- mjk1040
- Admiral
- Posts: 1506
- Joined: July 30th, 2015, 8:15 am
- Vessel Info: 1998 355 AC/MY "Deja Vu"
- Location: Savannah, NY
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Raw Water Impellers
I'd Rather Be Boating!
1989 Sea Ray Seville
1986 Carver Mariner 32'
1990's Thompson 22' Cuddy Cabin
1990's 4Winns 245 Vista Cruiser
1980's Thompson 19' Open Bow
- g36
- Admiral
- Posts: 1937
- Joined: April 7th, 2014, 6:07 pm
- Vessel Info: 1997 Carver 405
- Location: Soddy Daisy TN.
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Re: Raw Water Impellers
Crusader xli
The Black Pearl
Soddy Daisy Tn.
- waybomb
- CYO Moderator
- Posts: 2404
- Joined: February 5th, 2013, 9:24 pm
- Vessel Info: 1995 Boston Whaler Rage15
1987 3697 Carver Mariner
1988 Cougar 46 Kevlar Vee offshore
1969 15' Glasspar / 1967 Johnson Electromatic 85
1996 Boston Whaler Rage 15 - Location: Saint Joseph,Mi
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Re: Raw Water Impellers
Even though these pumps have flexible fins, they are essentially a positive displacement pump.
Fred
1969 Glaspar Avalon /1969 Johnson Electromatic 85
1987 Carver Mariner
1988 Cougar Kevlar 46' with triple blown 572 ci
1995 Boston Whaler Rage
Past - 1988 2807, 1989 4207 Aft
- mjk1040
- Admiral
- Posts: 1506
- Joined: July 30th, 2015, 8:15 am
- Vessel Info: 1998 355 AC/MY "Deja Vu"
- Location: Savannah, NY
- Has thanked: 9 times
- Been thanked: 236 times
Re: Raw Water Impellers
Waybomb-my thoughts exactly! However the Sherwood pump when new comes with 12 fin impeller. Now I have open cooling, so it may be possible more water is not a better idea. I have never seen the dash temp gauge go over 140 degrees, even though that may not be the exact temp of the engines. However as I stated above temp was not reading high or above 140, yet I would start to get steam coming out of the exhaust when the bad impeller was still in. After replacement at 140 I did not see any steam after running at idle as before.
I'd Rather Be Boating!
1989 Sea Ray Seville
1986 Carver Mariner 32'
1990's Thompson 22' Cuddy Cabin
1990's 4Winns 245 Vista Cruiser
1980's Thompson 19' Open Bow
- km1125
- Admiral
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Re: Raw Water Impellers
waybomb wrote:Source of the post Here's a thought - if there are less impellers, there will be more volume available for the water. Per revolution, less area taken up by the blades means more water moved.
Not necessarily. It's the displacement of the fins that moves the water. If you have 12 "displacements" per revolution you'd get more water pumped then if you only had 10 "displacements"... the rest of the water is just there for the ride.
Nice video of a pump running: https://www.youtube.com/watch?v=ECv1VwW6RTo
- waybomb
- CYO Moderator
- Posts: 2404
- Joined: February 5th, 2013, 9:24 pm
- Vessel Info: 1995 Boston Whaler Rage15
1987 3697 Carver Mariner
1988 Cougar 46 Kevlar Vee offshore
1969 15' Glasspar / 1967 Johnson Electromatic 85
1996 Boston Whaler Rage 15 - Location: Saint Joseph,Mi
- Has thanked: 50 times
- Been thanked: 396 times
Re: Raw Water Impellers
If the cavity is 5 cubic inches, and the impeller takes up 1 cubic inch, each revolution will move 4 cubic inches of water.
Same cavity, impeller takes up 4 cubic inches, there is only enough room for 1 cubic inch of water to be moved.
Fred
1969 Glaspar Avalon /1969 Johnson Electromatic 85
1987 Carver Mariner
1988 Cougar Kevlar 46' with triple blown 572 ci
1995 Boston Whaler Rage
Past - 1988 2807, 1989 4207 Aft
- km1125
- Admiral
- Posts: 3338
- Joined: February 28th, 2017, 6:04 pm
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Re: Raw Water Impellers
waybomb wrote:Source of the post Beg to differ.
If the cavity is 5 cubic inches, and the impeller takes up 1 cubic inch, each revolution will move 4 cubic inches of water.
Same cavity, impeller takes up 4 cubic inches, there is only enough room for 1 cubic inch of water to be moved.
Don't think so!
By that logic, I could cut all the fins off my current impellers and improve my flow 500%!!
- waybomb
- CYO Moderator
- Posts: 2404
- Joined: February 5th, 2013, 9:24 pm
- Vessel Info: 1995 Boston Whaler Rage15
1987 3697 Carver Mariner
1988 Cougar 46 Kevlar Vee offshore
1969 15' Glasspar / 1967 Johnson Electromatic 85
1996 Boston Whaler Rage 15 - Location: Saint Joseph,Mi
- Has thanked: 50 times
- Been thanked: 396 times
Re: Raw Water Impellers
Fred
1969 Glaspar Avalon /1969 Johnson Electromatic 85
1987 Carver Mariner
1988 Cougar Kevlar 46' with triple blown 572 ci
1995 Boston Whaler Rage
Past - 1988 2807, 1989 4207 Aft
- Midnightsun
- CYO Supporter
- Posts: 2831
- Joined: March 27th, 2016, 2:27 pm
- Vessel Info: The Midnight Sun
2007 41CMY
Volvo D6-370's - Location: Montreal, Canada
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Re: Raw Water Impellers
-
- CYO Supporter
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- Joined: July 10th, 2015, 9:58 pm
- Vessel Info: 1989 Carver 3807 Aft Cabin
- Location: Ontario, Canada
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Re: Raw Water Impellers
For our applications, the number of blades is more about head pressures than volume. The more blades, the higher the head pressures the pump can deliver. The thinner the blades, the more they flex, this is desirable in some conditions as they are more forgiving but the pressures are reduced. The thicker blades offer higher pressures but are less flexible which is a drawback in some cases such as liquids that carry more debris.
To ensure you're pumping to pump design spec, find out what OEM impeller the pump manufacturer originally called for, then you can cross-reference to the same number of blades, thickness, etc., then stick to that if it works for you.
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