Low water pickup mounting height
#1
VIP Member

Thread Starter

DOES ANYONE HAVE EXPERIENCE WITH WHAT THE MINIMUM DEPTH YOU CAN GET AWAY WITH ON LOW WATER PICKUPS.
I have Latham Marine low water pickups mounted on the transom near the bottom of the V on a 30ft Sutphen with twin 502s. With the front edge flush with the bottom, the back is right at 1/2" deep and they are 2 1/4" wide. That's a lot of drag and probably a lot of pressure at 75mph. Previous owners have installed a 25psi water dump regulator and they start dumping right after planned off around 25mph.
Just to reduce drag I am going to grind the back edge off a little at a time until the 25psi regulators don't dump anymore. I have water pressure gauges connected after the water pump. Anyone played with this - that could add a mph or two. I have heard that some boats have them less than 1/8" deep and round the front edges to draw up the water better.
Also, what is adequate water pressure??? I would guess 10-15psi. Thanks.
I have Latham Marine low water pickups mounted on the transom near the bottom of the V on a 30ft Sutphen with twin 502s. With the front edge flush with the bottom, the back is right at 1/2" deep and they are 2 1/4" wide. That's a lot of drag and probably a lot of pressure at 75mph. Previous owners have installed a 25psi water dump regulator and they start dumping right after planned off around 25mph.
Just to reduce drag I am going to grind the back edge off a little at a time until the 25psi regulators don't dump anymore. I have water pressure gauges connected after the water pump. Anyone played with this - that could add a mph or two. I have heard that some boats have them less than 1/8" deep and round the front edges to draw up the water better.
Also, what is adequate water pressure??? I would guess 10-15psi. Thanks.
#3
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If you can put a small grove in the bottom of the boat in front of the pickup about 1/2 inch deep or so, and then start to grind and test. It will probably wind up close to leave with original bottom. An easy way to do this is put a temporary pressure gauge on the sea strainer can, and start from now when motors run cool, then make changes. 20psi is fine just remember volume cools engines not pressure, you need pressure to get the air out of the block. This is all assuming you are getting clean water.
#4
Platinum Member


If your PU's are in clean water, it is doubtful you are going to want 1/2" below the bottom....that may end up being a lot of grinding. Every 1/8" in WPU length will likely show on the GPS. We switched from transom mounted PU's (1/8" below the bottom) to thru the bottom PU's. Best I remember, this was worth about + 2 MPH at 90+ MPH. Originally we used a trough in front of the thru-bottom PU's but ended up filling in the trough with the PU's totally flush with the bottom. Still get 10 lbs of WP mostly from vacuum. As long as you have positive WP, IMO the amount of pressure is not important. The goal is water flow not pressure.
#5
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iTrader: (1)

I was thinking of switching to these:
http://www.cpperformance.com/p-12543...ess-steel.aspx
Kinda tired of grinding away my current pickups to change the pressure.
Anyone have experience with them?
http://www.cpperformance.com/p-12543...ess-steel.aspx
Kinda tired of grinding away my current pickups to change the pressure.
Anyone have experience with them?
#6
Registered

I was thinking of switching to these:
http://www.cpperformance.com/p-12543...ess-steel.aspx
Kinda tired of grinding away my current pickups to change the pressure.
Anyone have experience with them?
http://www.cpperformance.com/p-12543...ess-steel.aspx
Kinda tired of grinding away my current pickups to change the pressure.
Anyone have experience with them?
#7

If you can put a small grove in the bottom of the boat in front of the pickup about 1/2 inch deep or so, and then start to grind and test. It will probably wind up close to leave with original bottom. An easy way to do this is put a temporary pressure gauge on the sea strainer can, and start from now when motors run cool, then make changes. 20psi is fine just remember volume cools engines not pressure, you need pressure to get the air out of the block. This is all assuming you are getting clean water.
You have experience?

#9
Registered
iTrader: (2)

I was thinking of switching to these:
http://www.cpperformance.com/p-12543...ess-steel.aspx
Kinda tired of grinding away my current pickups to change the pressure.
Anyone have experience with them?
http://www.cpperformance.com/p-12543...ess-steel.aspx
Kinda tired of grinding away my current pickups to change the pressure.
Anyone have experience with them?
#10
Platinum Member
