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View Full Version : Water Pick Ups, lowest drag ??



mphatc
11-13-2010, 07:55 PM
There's several options . .

1. through the drive
2. through hull
3. transom

Options 2 & 3 allow for adjustment of the depth . . .

My application of interest is my Magnum 27, which has 2 through hull bronze fittings 6' forward of the transom . . I desire to find a way to make improvements here as my drives have nose cones and closed off water intake ports . . . so do I leave it alone or change?????

Mario L.

maddad
11-13-2010, 09:55 PM
Mario, I don't think it's a good idea to use a Volvo drive to get the water. I picked through the hull, it was advertised as a "high speed" pick up. A little work with a router got it flush, bedding it in 5200 after a coat of resin on the cut glass keeps it secure and water tight. If there is any kind of real drag, I don't notice it in speed or handling. It's on the starbard side about 18" from the transom and 10" from the center line.
http://www.donzi.net/forums/attachment.php?attachmentid=59792&stc=1&d=1289703056

HIGH LIFE
11-13-2010, 11:28 PM
Mario, All the boats I have ever owned the the intake on the transom. The pickup was app. 3' wide X 6" long , cast bronze w/ a 1" thru hull fitting thru the transom where I installed a ball valve, hose to a sea strainer, than to water pump. P.S. I have 2 in stock that were on my previous MAGNUM. "HIGH LIFE"

gcarter
11-14-2010, 07:18 AM
In the past, I've had issues w/things that were bottom mounted off center causing trim issues. These were'nt my boats, I simply noted the problems.
I've had good success w/Stainless Marine transom mounted pickups. The model I've used extended below the bottom +/- 3/8" and was about 1 1/4" wide and had a 1" NPT connection inside the hull.
I believe a speedo pitot can cause drag although it's insignificant until the speed is over 100 MPH because the water in the tube is deadheaded and in compression.
Conversely, a pickup doesn't add any appreciable drag as the water being scooped up is carried away in the internal plumbing w/little backpressure. I suspect that the only drag associated w/a pickup is the the water being scooped and forced into a 90* bend, plus the difference of the inside and outside areas of the pickup material (which is pretty small). I think it would be pretty easy to calculate both of those numbers.

http://www.donzi.net/forums/attachment.php?attachmentid=54334&stc=1&d=

The Hedgehog
11-14-2010, 08:34 PM
I have one like GCarter's SM. I think mine is a Latham not that it really matters. I use a water pressure gauge and my pickup works great. I have run north of 100 with no problems. I give it a thumbs up.

mphatc
11-16-2010, 08:59 PM
Thank you all . . .

Presently the boat has two like Madad's picture, but not in equal port starboard locations . .plus they are 6' forward of the stern and I feel they'll disrupt the flow under the hull.
I like what George's picture shows . . and most of all the comfort of someone using these at speed with a water pressure gauge . .
I'll price out some options and see what is reasonable. IMO some of this offshore stuff is grossly overpriced!

Mario L.

gcarter
11-16-2010, 09:50 PM
Thank you all . . .

Presently the boat has two like Madad's picture, but not in equal port starboard locations . .plus they are 6' forward of the stern and I feel they'll disrupt the flow under the hull.
I like what George's picture shows . . and most of all the comfort of someone using these at speed with a water pressure gauge . .
I'll price out some options and see what is reasonable. IMO some of this offshore stuff is grossly overpriced!

Mario L.

Mario, the SM pickup is, I think, pretty expensive, at about $160 each, I think. But they are beautifully made and very well built in SST.
I've been able to find several on eBay for about $50.00 each.
You have to be patient because they don't come up very often and a search of "Stainless Marine" turns up a bunch of hardware you have to sift through. But one thing you have is time.