Low water pickup depth below bottom
 

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 plan on cutting water channel groves into the bottom of the hull feeding the pickups and allowing to raise them higher.

3" below the bottom 92 mph I'm at 28psi

The pickup @ 3" deep cost me 3mph but the motor doesn't get hot.

you must have steps.

mine are almost level w/ the bottom of the boat,,maybe 1/8th" max.25-27psi of water pressure at 90+mph.

was told to do that by Ritchie Sutphen,said I may get alittle speed out of it.

On a flat bottom 1/4"-1/8" at the rear is normally enough.

Latham has the depth built into them as long as the front edge is flush to the bottom that is where Latham says to install them. Cutting some grooves in the hull is a good idea. Latham creates the angle in the pickup. I just install the same one on my 26 sutphen and Lathams instructions said to mount front edge flush with bottom. Kind of wish I would have ground some channels now though.

[ATTACH=CONFIG]533773[/ATTACH]Here's the on I just mounted, unfortunately I don't have any side angle pics.

My suggestion is to call Sutphen and see what their suggestion is to reach your goal.

I'd put the water pressure line or sender up on the thermostat housing.as for grinding,take a little at a time or you'll be grinding into the hull alittle to gain back water flow.bending the trailing edge up a little to help as a scoop works,just remember to keep it down more as you'll have less pick up in the water.

My pickups are rectangular shape. The bottom side that faces down, has a plate welded. It is then drilled with a bunch of small holes for water to pass thru . it filters out any debris from entering the system.

Coolerman made adjustable pickups if I remember correctly. That may be a option for you also.

My water pickup is maybe an 1/8 Inch below the bottom of the boat at most.
It was the same on my Pantera. Both had/have plenty of water pressure and no issues.

thanks for info.
Sutphen30 - it doesn't have steps.

Ya'lls info gives me a little more confidence that I will be able to take off quite a bit from the just under half inch they are now but I think best to go 1/8 at a time until I get the pressure down to 20psi or so as long as its cooling good. Hopefully may gain a couple mph if I end up at only about 1/8 deep. Will let yall know but will be a few weeks, rebuilding one motor now.

I know you don't have steps.was asking Black baja,3"'s is-really deep.only saw it like that on my friends formula.water pressure is perfect at 110mph.

Yes, stepped hull. Every boat is different when it comes to water and cooling motors. Some boats have water problems. Proper setup of a water pickup is trial and error. There is no magic formula.

have you thought about running low water pick ups and ditching the transom mount.may pick up a lot of speed.

Been there done that even tried modifying low water pickup on the drive. Nothing worked. Had a transom mount pickup right off the bottom of the hull (boxed one just like everyone else) no go. I think the steps out a lot of air in the water I was seeing 18psi with drive pickup and flush transom hull pickup. Motor would get hot. Only thing that worked was burying the pickup. I talked to a guy that has rigged a ton of boats he said sometimes you get a hull with these issues.

Its got bravo ones so if it came with the factory hose setup through the transom plate from the standard water pickups everything would be fine. Previous owners had problems with corrosion at the fitting going thru the transom plate and choking off water flow. Very common problem.

THe problem is they should have just kept it simple and corrected the corrosion issue. THen no deep scoops to drag the boat down possibly 1-3 mph, and much much less mud/sand is picked up by the the standard Bravo pickups when beaching a boat like we don around Lake Charles, La several times each day when were are out.

I agree,,alot of trial and error till it works.

There is a proper way of setting up an offshore pick up. There are adjustable ones and others that have to be ground. In most cases the trailing edge should be around 1/16 to 1/4 " below the bottom. The best way to determine the X height is to pace a Tee & a 0 to 15 psi gauge between your pick up & sea pump; and have a water pressure gauge for the motor. You need NO MORE then 5psi ram pressure @WOT. anything more is just a waste and will be a speed loss. When I did testing of sea pumps on a pump dyno, the magic # was 5 psi @ wot. Then check your block pressure. Anything from 10 to 30spi is good there, don't get all hung up on thinking you need a ton of block pressure, you have the biggest supply of cooling water. If your worried about steam pockets drill & tap the back of the intake for air bleeds. If your pick up is more than 1/2 dragging, then fix your bottom. I have seen guys run high block pressure & blow buy in intake gasket &/or wonder why they have water in the bilge after a run???
Oh forgot to add you also can do this with the drive pick up by drilling and tapping s/s set screws in the holes or add hole as needed. Its all in the fine details guys & taking the time to do thinks right; NOT "its ok it works for me"....

That's good information , thanks .

Sounds good to me. I was going to grind off until I see 20psi motor pressure and stop there.

Doing that you will be fine

Where is the proper location of water pressure readings? Mine is right after the freshwater pump on the PS cooler and before the engine oil cooler which acts as a strainer somewhat since the exchanger holes are only about 1/8 to 3/16". I am going to move it to the engine as I think the reading should come after the engine oil cooler which can restrict the water.

Should it be on the thermostat housing below the thermostat, or down on the block?

Should there be much difference in pressure between these two locations? Assuming a clean block.

I like to tap into the back of the intake to get my block pressure. Some guys tee into the block drains, only problem there is soot & sand will plug your sending hose. Before the thermostat will be fine. And yes , if you take pressure readings taken before restrictions, like in coolers that can have blockage, you will see high readings at that point. Too much block pressure can blow thru your intake gasket into the oil galley.... bad buzzzzzzzzz. Like I stated in earlier posts, you don't need a ton of block pressure. Its about water FLOW (GPM) not pressure . http://youtu.be/HWGcvwHZSE8

thanks bawana

you sure thats not youre speedometer pickup. :-) jesus how do you keep that from getting ripped off the boat ... you must always have a rooster going :))))))))) just playing

Mine were 1/2" deep and the pressure was getting over 30psi@ 4000rpm
At 3" it must be like 70psi lol

Over on River- Daves , there's a thread from Teague about installing water pick-ups...

My boat has two steps there is roughly a 6" difference from the bottom of the first step to the pad. This is on a 25' bottom. My theory is the water is getting a lot of air in it. I'm seeing 28psi at over 90mph I don't think its all water air compresses and shows up as pressure. Not many know this but some boats have very elaborate water systems to get the air out of the water b4 it enters the motor to cool. Believe me I went through the ringer with this thing to try to keep it cool. Dual stage pump, two other pumps, hardwall hose, softwall hose, water hose in the transom assembly, t-bolt clamps, worm gear clamps, double clamps, 5200 on nipples then clamp the hose, rigger up a leak down tester, modified the low water pickup many many times, tried low water pickup in conjunction with transom pick, sea strainer, no sea strainer on and on and on. Believe me I don't give up to easy but I was starting to think about used motor oil and a propane torch to take care of the problem. I buried the new adjustable pick-up and bam. Problem solved. The other nice thing about having the pickup buried I don't have to ride with one tab down and one up to keep the boat level. Both tabs up she's dead level. You wanna talk about a fun ride without the tabs. Let's just say that's how I ended up breaking the cockpit...,

TTT for sonic 700