BLUEMAGIC

I have two -4an lines off the back of my intake T'd into one -4an line to bleed out any air pockets. I would like to lower my water pressure a little more. Considering putting a -8an line off the front bung of my intake to a threw hull fitting with a ball valve to adjust pressure as needed. I have crossover with bypass and 5/8 restrictor in thermostat housing to build temperature. Is this a good location to bleed off water pressure? my concern is whether or not it would starve my exhaust of water being drawn from the front of the intake near the thermostat housing?? any input would be appreciated.. thanks

BLUEMAGIC

curious if this is a common setup??

ealesh33

What kinda pressures are you seeing at cruise and WOT? You using drive to pull water, or external pick up? Bravo or imco? If bravo is it a low water, side, or dual water pickup?

BLUEMAGIC

I have a transom mounted pick ups and they are adjusted as high as I can before introducing aerated water. At cruise my pressures are around 20 pounds. Have not opened up knowing pressure will just climb. I would like to knock it down to 10 pounds around cruise and 20 at wot. Would it be a good idea to pull water from the front of intake to a threw hull fitting. I have a ball valve there where I can adjust flow to get the pressure I want. Does it matter where you bleed water from on the intake? Is it possible that dumping water from the front would rob more water for the headers vs dumping water from the rear of the intake? Again I have bypass hose with crossover and 5/8 restrictor in thermostats housing to build temp.

ealesh33

You should get a WOT pressure, it may not climb that much. On mine with an imco lower I see 18lbs at cruise and 22ish wot. That's with a crossover no bypass, no restrictor, just an open flow system. I don't think you need to run a pressure relief until you know what the wot pressure is, at wot 20-25lbs is what most shoot for with an absolute minimum of 15lbs. I'm not a fan of the crossovers with bypass, in your case pressure isn't an issue, but often times pressure and block water flow is cause the bypass is so large. What does your oil temp run at cruise and wot? What's the reason for external pick ups vs using the drives?

BLUEMAGIC

I run oil thermostats so my oil temp is good I run 120 water temp. I'm just curious as to weather it matters to dump water pressure from the front vs the rear of the intake? I like the idea, of relieving pressure from the front with an 8an line to a ball valve at threw hull fitting to get the correct flow to get my pressure where I want it. I would like to leave my 4an line in the rear to relieve air pockets. Is it possible water would flow straight to my 8an dump and pass right by my 5/8 restrictor in the thermostats housing? Or would it flow out of the restrictor as it would my 8an dump ?

ealesh33

Water is going to take the path of least resistance, hard to say what path the water will take once it's getting pressure from the block. You have an oil thermostat so oil temp isn't a big concern here. The -4 crossover lines in the back of the intake dumping off is a good thing. If it was me I would first get a wot water pressure reading. If it was too high, then I would block off the bypass and remove the restrictor. That way all water goes through the motor, water in water out and has 1 path. I get what your asking, but no way I would want to add more rigging to the boat, more things to fail, and drill extra thru hulls when it doesn't have to be that way, that's why I'm asking the questions I am. Simple is better. JMO

indysupra

I would not bleed off the front with crossovers. The idea behind the rear lines with a crossover is to bleed air and insure flow thru the engine not just the front of it.
I know you don't want input other than what I stated above but who is to say that at wot/top speed you won't pickup air at the pickups? The pressure could drop. Had that same issue with a friends 35.

BLUEMAGIC

I would like to keep my restrictor in place to build water temp. Without it temperature won't move. Does using the front bung on the intake to dump water pose a problem? Does the by pass hose supply enough water to cool the headers if flow is decreased threw the restrictor plate? That is main concern.

ealesh33

The issue with the crossovers with bypass are they bypass too much water through the exhaust. I have personally seen a crossover with bypass drop block pressure to 0psi at wot even with a Tstat, so started restricting the bypass hose only and pressure started to increase. So for that reason I'll never run a crossover with bypass again, as there is no way to tell how much water is actually flowing through the block even with dumps from the back of the intake. This same thing happened on multiple boats, one had to have an external pick up installed to get pressure. So It's either a circ pump and Tstat set up or crossover no bypass or Tstat set up for me.