tomcat

I have been reading the threads on sea pumps, and I don't want to hijack them, but I have some questions. I know that the volume depends on inlet pressure (speed) and outlet pressure (restriction of block and plumbing) but what ballpark are we in?

Question #1:

How many gpm does a sea pump actually move?

Stock merc pump - ? gpm
Hardin single stage - catalog says 20% more than Merc?

Question #2:

How much engine horsepower will a single stage pump support safely?

Bonus Question:

When you use a triple stage Hardin and a single 1 1/4" inlet line is plumbed to a common riser that serves all three stages, (see attachment), do you think the volume delivered to each stage is the same?

Thanks,

Tom

CPPerformance

Well theres no hijacking taken and were more than happy to answer any questions. Actually you almost answered all of the questions with your entry statment.

What we can answer are some static examples.These examples are from our own testing procedures with our own equiptment.

Stock Merc Pump: Approximately 10.5 GPM per 1000 RPM.
Hardin Marine Single Stage Pump: Approximately 13 GPM per 1000 RPM.

These figures are based on 1" common inlet and pump exits.

This is probably the most debatable question out there and it really requires "Your" engine builders input for their specific application. Supercharged, naturally aspirated, etc. Engine builders have varying theories. In this area the pump may play multiple roles in the overall engine package. Some builders want to achieve maximum flow and cool water at all times, other builders want to slow down the water so that it spends more time in the engine. Builders even debate water pressure characteristics.

We build our pumps in custom configurations to our customers specifications and they (the customer) truly determine this answer. I am sure you have witnessed single stage pumps on everything from a 500HP application to a nearly 1000HP application, the correct use is determined by the end user/engine builder.

In a properly configured cooling system that provides adequate supply the answer is "Yes" it will.

In fact we build some individual fittings to work with the three stage common inlet. Part number 625-4402 - This fitting is a high flow 1-1/4" NPT x 1-1/2" hose barb and provides a 1-11/32" (1.7671 hole area) inch inlet diameter as opposed to say the standard 1" NPT common inlet with a 1" I.D. inlet ( .7854 hole area). This larger I.D. fitting when coupled to an adequate water supply provides an additional 30% of water flow.

Lastly as stated by both us and our competitors, as the boat speed increases and water pressure climbs there comes a point and time where the pump practically operates as the regulating source due to the increased water volume.

We hope this answers your questions!

Raceangel77

Hi the boys at CP are correct , and as they will tell you the flow requirement is dependant upon your engine set up, and they are correct in stating that a single stage can be run on a wide range of engine sizes.

We have flow rates at 4000rpm , but our results show that the stock mercury pump has the best flow rate at 42 gals/min at 4000rpm. The KPM and Hardin lets say are very similar as you would expect. But please remember that both of these pumps have to be designed and configured for every possible use so the design can never be optimised , unlike the merc pump. The flow of both the KPM and Hardin pump will be more than enough.

However, what might effect your flow is the plumbing , Remember that the pump is working ,when at idle, in two phases. One side is sucking and the other pushing in its simplest form. If you are trying at idle to draw water through a pipe system that has lots of bends , fittings etc this will dramatically effect your performance at idle until you are on the plane. Also watch for air leaks

Simple calculation.
In its purest form with no restrictions your three stage pump should pump about o.26 gallons a second at about 500 revs idle speed. To pull this amount of water through a 1 inch pick up would register a pressure of about 3 psi . but remember that you have pipes and bends that all reduce the flow. But most pumps would have an operating head well in excess of this requirement and you would obviosly pump alot more than this. With out knowing the exact set up it is difficult to determine.

With a 11/4" input you will have more than enough flow.

If you email me the following I can do the calculations for you on our water system simulation programme,
Pickup dia
total length of hose
strainer input and out put size,
number of 90 degree bends
number of 45 degree bends

Our competitors are also correct in stating that your requirements may want the water to stay in the engine a bit longer. The danger is that if you have to much flow that the water does not spend enough time in the engine to achieve full heat transfer. The water on the outside of a bore will tend to dwell with high laminar flow running through the center , and water does not transfer heat in a homogeneous manner. Think about standing in a pool.! your feet are cold with the water getting warmer the closer it gets to the surface.

Also Too little flow and the engine overheats and creates damage.



What I can tell you is that a number of our customers that produce big HP motors seem to run with two stage. They also feed each chamber individually with 1 inch pipe which is connected to a junction with a 1 1/4 main input which we make for them along with the pumps. Reggie fountains record v bottom ran a two stage and that was packing a lot of power.

My initial reaction is that it might be prudent to try a two stage first and save some money.

If you phone fred at trick marine we have pumps and fittings that you can experiment with so you can decide which is the best application. These are pumps that we send to customers if they cannot decide what they need. They are a bit dented but ok in side. All we ask is that you pay for the shipping and leave a returnable deposit of $150. At the end of the day they are not cheap and we would hate for you to make a mistake.

Ps the pumps you saw on the web thread are now over a year old and most of the features completely changed or improved. These will appear on the web this week or see our website. teamkpmracing.com

Jules morgan
KPM

Cord

iTrader: (2)

On my past boat I had two flow restrictors at 20gpm each. At idle I had some suprising velocity coming out of them. This engine rarely built water temp, so I feel that the restrictors were still too large as there was too much water volumn moving through the engine. Next time I'll try some 15gpm restrictors and see what happens.

articfriends

iTrader: (1)

Jules, I am running the kpm body and impellor with my stock merc front cover and pulley. It was alot more work than I expected to install the retrofit/rebuild kit but regardless it is in place and it works. My questions are the motor seems to run 20-30degrees warmer than it did with stock pump from 3500 rpm's up but I also changed the power output when installing the pump. I'm running aprox 950 hp, I was running around 750hp before,I'm using a simple crossover that I have always used in the past and plumbing is the same with no added restrictions. I'm still sucking water through the stock pick-up in the outdrive,same outdrive so the net positive suction head distance should be the same. How does sucking water through the drive compare to using a external pickup?Would I still have this 90 plus psi at 85-95mph on the suction side?I'm concerned my innercooler(which is cooled by water tee'd off motor) might be getting hotter water than I'd like it to when engine temp climbs. The temp is stable though,it isn't like it gets hotter and hotter when it climbs,its just it climbs from its normal 100 degrees operating temp to 120-130 degrees. I personally think that I should probably just get a external pickup just for the innercooler so its water flow increases proportional to boat speed and engine would get benefit of all cooling water cooling it. I'm curious how returning to a stock merc pump would compare but it's extremely difficult to get to pump in my boat,any input would be greatly aprecciated,Smitty

tomcat

Thank you for your replies. I'm leaning towards the three stage because many engine builders use two stage pumps and have their preferred plumbing arrangements to coolers and block. If we add a third stage dedicated to the intercooler we "should" know that the intercooler is getting the design flowrate.

Just looking at the area, if one stage usually takes a 1" I.D. hose (0.785 in2), then two stages need a 1 7/16" I.D. hose and three stages need a 1 3/4" I.D. hose. These sizes might be overkill in practice since there is lots of pressure on the inlet at speed. I don't think there's a problem getting a big enough hose into place, but feeding three stages from one hose requires some thought about how you split the flow.

Mbam

I respectfully take issue with the idea that too much water flow will reduce heat transfer. What you say is true if the goal is to heat the water, but all we care about is cooling the engine. Increased flow will remove more BTU's. The net temp rise in the water is not as great, but there is more of it.

WETTE VETTE

Smitty,
Your stock side pick up drive will not generate as much ram as an Imco or thru transom pick-up. Even if you have a stock type LWP it will not compare to the Imco or a thru hull. Actually I like the design of the stock stuff because normally pressure controls aren't required. My motor isn't as powerful as yours, but with the same KPM pump the temp runs right at the thermostat setting of 142 regardless if I am cruising or running 6300 RPM. I do run an Imco lower and dump a hell of a lot of water through 2 dump valves to maintain 25 PSI maximum pressure.
Craig

hillbilly24

I've been in several discussions over the years about just this topic. Execissive water flow does degrade cooling ability. The closer to molecules are to each other temprature wise, the faster they meet in the middle. What this means in a cooling system is that the hoter you let the water get, to an extent, before it exits the engine the faster it will absorb heat. If you don't beleive me take two identical frozen pieces of meat, same weight aproxomite size ans so forth. Put each in an identical sized pot with the same amount of water in each. Fill one pot with hot or boiling water and the other with rom temprature tap water, see which piece of meat reached room temprature sooner you will be suprised. it is the same concept, the closer the two are in temprature to begin with the sooner they will equalize. I hope this made some sense cuase it does in my crazy mind.

bob

When I was running Bravo boats one of the first changes I made was going to a remote pickup due to the inherent weakness in the intake hose 90 deg bend in the transon assy. Is that hose design still be used?