CcanDo

Recently,there was extensive discussion about this subject.My understanding is, the pumps are all basically designed to deliver 30 PSI pressure and various volumes from pump to pump.However,the rule of thumb,in that discussion,was "ADD ONE PSI PRESSURE FOR EVERY ONE MPH ABOVE 30 MPH".Based on that,the ram effect would put the PSI at 100 with a speed of 100 mph.That is, unless the pump also serves as a pressure regulator VIA distorted impeller vanes.If that is correct,how much aeration (bubbles) occurs,after the pump.Therefore,should there be a pressure relief valve before the pump inlet to bypass the pump to a over board dump? .......Last,other than debris,should the sea strainer w/ a air dump be after the sea pump rather than before?

CcanDo

In other words, relative to the above post:Any insight, someone may provide, would be much appreciated. It seems to me,the water plumbing diagram and method of flow is as important as any other part or component (s) of the engine. For example,some have used, routing from the sea pump to a freeze plug on each side of the block,instead of sea pump to the traditional cross over. However,with that I worry about thermal shock....... Ideally,I would like to move as much water volume as possible,at the lowest pressure,with the least amount of aeration (bubbles) and least amount of negative influence on the sea pump.

MOP

It is a good idea to limit the pressure, Merc offers a pricy relief valve or you can rig a simple check valve before the sea pump. The idea is the pump will hold it shut as long as the demand is higher then the pickups pressure, at high speed the check valve will open the water can be used to feed a shower or just dumped. Rigging a check valve is pretty fool proof, I have a slow 65mph boat I swapped from a Blackhawk to a BravoX dual pick up. After a couple of WOT runs I found water in the bilge, It was forcing its way out of the strainer cap. The dual pick drive adds a lot of pressure to the system as does transom pickups. At speed like mentioned above the pressure gets real high, high pressure can blow hoses and on raw cooled engine can cause head gasket weep-age. I believe in letting the raw water pump function as designed, it is not a "positive" flow pump! The rubber impeller when subjected to the back pressure that builds inside the engine as speed is increased "will bend away from the pumps bore and not pump as much, all over pressure conditions stem from the water pickups not the pumps!

Phil

monstaaa

i have installed both items mentioned above.
on this instalation i used a -12 line overboard from a blow-off valve which is plumbed into the strainer/ water catch can, as well as a -4 air bleed. the bleed must be installed below the water line or it will cause the pump to lose prime by breaking the suction. after on plane the natural water psi will bleed off here as well as getting rid of the air in the cannister.
the blow-off valve is set to 35 psi .
the water pump is a 2 stage billet unit that is internally by-passed( according to spec).
the exhaust dumps over board. as does the intercooler. the water is also dumped from the back of the intake.

one thing i have heard mentioned which is as important if not more(especially when using a big cube eng.) is volume. another words the volume of water and how disturbed or undisturbed it is.. travelling thru thw water system

in the above said install the theory was to allow the pump to use as much water as possible that is un-airated, by bleedind it off and letting the blow off relive the excess psi( which also causes issues) before the water even reaches the pump, you end up with pretty clean water.any excess air or pressure at this point is relieved by the dumps in the intake, which are -10. this method has produced about 20-24 psi at speed(well over the 100 mark) and very exceptable temps. good pressure and good volume.
sorry to ramble , just sharing.

CcanDo

There are a few other points you may care to discuss......Such as;we have opened up the heads,and port matched a larger opening on the top of the head to a enlarged opening into the manifold.The manifold water passage has been ported and polished.......The original manifold water dump is replaced by welding on a new 1.25" bung,which receives a deburred,sweeping 90*elbow aimed at the headers.The 90* fitting receives a 1/2" bung for tying both sides of the manifold together.That cross over is also used for terminating -6 hoses coming from the steam ports at the rear of the manifold......The hose coming off from the 90* fitting toward the header is 1" ID....... Fabricated headers are believed to have varying tolerances between the two stainless pipes,effecting volume and imbalance.......Therefore,we have a "y" fitting,with one leg going to the header distribution manifold and the other leg going to a pressure relief valve,then on to an overboard dump.(I'm not sure the valve shouldn't be replaced w/ a calibrated washer and tuned w/ a flow meter).....The head gaskets are port matched to the manifold. The next sets will have graduated holes along the side of the gasket......Please keep your thoughts coming!

CcanDo

There are a few other points you may care to discuss......Such as;we have opened up the heads,and port matched a larger opening on the top of the head to a enlarged opening into the manifold.The manifold water passage has been ported and polished.......The original manifold water dump is replaced by welding on a new 1.25" bung,which receives a deburred,sweeping 90*elbow aimed at the headers.The 90* fitting receives a 1/2" bung for tying both sides of the manifold together.That cross over is also used for terminating -6 hoses coming from the steam ports at the rear of the manifold......The hose coming off from the 90* fitting toward the header is 1" ID....... Fabricated headers are believed to have varying tolerances between the two stainless pipes,effecting volume and imbalance.......Therefore,we have a "y" fitting,with one leg going to the header distribution manifold and the other leg going to a pressure relief valve,then on to an overboard dump.(I'm not sure the valve shouldn't be replaced w/ a calibrated washer and tuned w/ a flow meter).....The head gaskets are port matched to the manifold. The next sets will have graduated holes along the side of the gasket......Please keep your thoughts coming!

CcanDo

Has anyone tried the new Stainless Marine sea strainer?

monstaaa

they work well. as for the dumps and y's on the rear of the engine , have you found the balance yet?

CcanDo

Hi monstaaa,

We have not run the engines,in the boat..However,plumbing is done as discussed above with everything but tail pipes in the place.

The tail pipes have an elbow in the exhaust stream W/an orifice, screw in bung for discharge of the header water...Therefore the headers and tail pipes will be kept full...The remainder will be metered flow and go out through the Y...The orifice diameter is subject to pipes and water temp....
Theory is,there should be less thermal shock and blued headers.

We have the new style Stainless Marine Sea Strainers...The lite springs are in the pressure relief...Whereas,there are reports of cometic gaskets leaking @ high pressure, we'll leave the lite springs in and see how everthing works....Any suggestions ?

Also,we need 60* gauges for oil and water...and single gauge/dual needle boost and vac....got any ?

502ss

iTrader: (3)

Along the same lines, Can anyone think of a reason why it would be a bad idea to place the oil cooler after the sea strainer but before the pump, Instead of after the pump? I am re plumbing my twins and this would make for a lot cleaner install. The only difference I can think of is that they will be on the suction side instead of the pressure side, but only when the boat is sitting still, Once you start to build speed the suction will turn to pressure as you mentioned above.