comparing water pickups

[iridebikes247]

Hey I was wondering how have most users fared using bottom flush mount water pickups? I have some installed on my big cat with them mounted at the very back of the hull the boat picks water up in the lines but it would see it only really starts shooting water out at speed anything over 40mph. I have my speedmaster rudder on another boat and have used the small brass tube transom mounted water pickups and they suck in water and let it out going even 10mph. Do these create significantly more drag? I just want my more expensive electronics to stay cool and for some reason I feel I'm not getting enough cooling. Thanks guys.

[kingwrench]

Every thing in the water creates drag run and take temps adjust to suit I make my own pickups for my cats and cool the sc first . On my saw boats I don't use jackets or cool the motors

[lenny]

iridebikes247 have any pictures of your setups in the boats ?

[siberianhusky]

How can you "feel" you aren't getting enough cooling?
Are things too hot after a run? What are the temps?
IR temp gun is only a couple bucks, everybody should have one in the field box. Only way to really know what your temps are.
Not really a grey area, either your temps are hot or not! If not the cooling is working fine.

[iridebikes247]

I will post a pic later. No temp gun and no things aren't getting hot...yet I'm about to prop up. When running my smaller boats I can see water spraying quite some distance out of the outlets I don't think the same amount of water is flowing out with the flush pickups. I ordered through hull water pickups from kintec for $1.75 each only they're the brass tube with the lip on the end, it will increase drag but also water flow. My boat runs about 85mph btw and this is the first time I've used a flush mount.

[SirBudman32]

I used those same thru hull pick ups from Kentec in a Genesis I had. I mounted one one each side of hull and they worked very well. You can cut them down if you want. just go a little at a time.

[lenny]

I heard these work very good for water flow,
http://www.offshoreelectrics.com/pro...?prod=oct-ocsw
large__31_03_2007_11_02_octura_water_pickup.JPG
Or this one to mount to the transom.http://www.offshoreelectrics.com/pro...prod=ose-80410
ose-80410-pickup_small.JPG

Hears a link with a lot of info on cooling and thermal transferring. http://forums.offshoreelectrics.com/...r-pick-up-ever!
Like optimum thermal transfer occurs when the water is there long enough to absorb the heat.
So did a test, And made a exit water limiter to keep the water around the motor can longer,
And the temps where a little lower on the motor.

[sundog]

Hears a link with a lot of info on cooling and thermal transferring. http://forums.offshoreelectrics.com/...r-pick-up-ever!
Like optimum thermal transfer occurs when the water is there long enough to absorb the heat.
.

I believe that is a myth. Slowing the water cannot cool better. That is old school thinking, there. I think that both Don and Jay had it wrong. It's basic science 101. It does not have to 'hang around' long enough to absorb the heat. Heat goes to cold. The colder (faster) it is, the faster the transfer rate. Ice cube to banana. Think about it, if you slow the rate and the cool water line heats up (because it's 'absorbing' the heat) at that point it is giving up heat, not transferring (removing) it, and thus not cooling as efficiently or effectively. Silly, really. If you slow the rate and it cools better, there is something else going on.

On the question of thru hull pickups. they do not need to protrude from the hull (stick out) to 'catch' the water flow. Flush mounts will flow water just fine, and without unnecessary drag. They do need to be at an angle, to direct the flow. And I believe in a modern cat with a stepped hull, the best location for continuous flow is at the rear of the first step in the sponson. Not the transom (which can break free of the water as the transom lifts at speed).

[Fluid]

You can argue this silly point all day long if you want, fine by me. Those with a science background know that water has a high specific heat - meaning it takes time to absorb heat and it takes time to lose it. That is basic thermodynamics and it trumps "comon sense" thinking every time.

Bottom line - believe what you want, the heck with the science, who needs it. We all know that mirror-finished props are faster than any other finish, that lightning never strikes the same place twice, that we get colds from sitting in drafts, and that dropping a penny from the Empire State Building can kill a pedestrian below......:


BTW always put your through-hull water pickups near the transom on cats, not forward where the hull may rise out of the water as it rides on the back of the sponsons. That back part of the sponson is always in the water and because it supports the back of the hull (where the CG is) it will always have the highest water pressure under it. It is the water pressure under the sponson which fills these fittings, unlike a rudder pickup which will begin to flow water at relatively slow speeds. The through-hull fitting needs more speed and the resulting pressure to fill with water. A poster above demonstrated that fact rather well. Personally I have used the through hull fittings on fast boats and they work great. They have no less drag than a rudder pickup however.



.

[Heaving Earth]

I agree with sundog.
If a thermostat on your car gets stuck open the engine doesn't get hot enough

[Heaving Earth]

I suppose if you're trying to make coffee with the water coming out, then restricting it is necessary, but were not trying to heat water here, we're trying to keep the motor cool.

[sundog]

BTW always put your through-hull water pickups near the transom on cats, not forward where the hull may rise out of the water as it rides on the back of the sponsons. .

Now, think about this, Jay. If you look closely at a stepped cat hull at speed, it is running on the formost step of the sponson. The rear of that step is in high velocity water, which is an excellent place for a water pickup. And if the transom pickup is the flush type, at high speeds it may come completely out of the water (when running on the bottom half of the prop). There was a time when a cats sponson would be mostly out of the water, but not with a modern 3-point boat. This is what I am talking about when I refer to old school info, just like the heat transfer misinformation. No offense, Jay. If I am wrong, please explain where to I can understand you. I am thick headed, you know.

[Heaving Earth]

It would be interesting to do an actual test. Run two of the exact same motors at the same voltage, and use two different sumps out of the same barrel of water to each motor and see if more or less flow works better.

[sundog]

I suppose if you're trying to make coffee with the water coming out, then restricting it is necessary, but were not trying to heat water here, we're trying to keep the motor cool.

Thank you. If you restrict the water coming out, it gets hotter. Not because it wasn't absorbing the heat in the first place, but because it is not being removed as well. Yes, I think that explains it much clearer. If I burn my hand, I put an ice cube on it, because it transfers (gives up) the heat faster than something at room temperature. It doesn't take a physicist. Thanks, man.

Sorry about hijacking your thread there, IRideBikes.

[Heaving Earth]

-)
Even full size boats use thermostats to restrict the amount of cooling so the motor can reach optimal temps using the water from the lake. Which tells me that more flow = more cooling. What argument can be made against that?
I've read about cooling computers CPUs with water and guess what, they use more water flow than less.