Engine cooling from suction housing

[CcanDo]

I am in the process of installing a 750hp Sterling APBA supercat engine in my jet. I am concerned about cooling using the 3/8" pipe bung in the suction housing to cool the engine. In our offshore boats, inlet line is 1 1/2" to a dual stage sea pump, then 1 1/4 to each side of water crossover. I apreciate the jet pump is pressurized, but am concerned about volume.
How are you guys cooling your 750+ motors?
Thanks

[poncho-pwr]

The water supply from the pump is PLENTY for any motor you want to throw at it!

[CcanDo]

I am sure the 3/8 pump outlet will show a decent temp on the guage, but the consensus in the offshore world is preventing water vaporization against the cylinder wall by packing as much water as possible through the block. Run the engine as cold as possible, then regulate internal expansions through oil temperatures using big oil coolers and cooler thermostats.
I use my jet as a lake boat (20'mod vp) and like to blast across the lake once in a while, rather than just a 1/4 mile spurt.

[poncho-pwr]

Trust me, it will run cool as a cucumber! It will most likely run cooler than your offshore setups run. I don't like to run a thermostat in a jet boat because I don't see the need. The only time your jetboat motor will run any kind of temp at all(above160) is when you are just idling around for long periods of time. As soon as you get on the gas it will cool way down even at cruising speed. A jetboat engine is probably one of the hardest engines to get to warm up as far as water temp goes if you are not running a thermostat or a control valve of some sort to limit the amount of water flow through the engine. That jet pump is a HUGE water pump that will give you all the water volume you want or need, and I don't see water vaporization against the cylinder walls being an issue. Oh, the big oil cooler is always a good idea in a jetboat..The bigger the better!

[Moneypitt]

My son has a jet with a Jacuzi pump in it that had one 3/8ths pipe out of the jet. It wasn't enough!! I added another 3/8ths pipe out the other side and it sure helped alot. My Berkley has 1/2 pipe (3/4 hose) and I've never had any heating problems, and that runs to a "T" (5/8ths hoses) to the inlets on the engine. What type pump do you have?............MP
PS, what is an APBA engine?

[CcanDo]

Pump is a Berk JG that has 3/8 outlet. Pump is set-back so a line runs from suction housing to transom / bulkhead fitting / to tee then to block. There is not a check valve or valve to control water flow. All outlet water runs to Lightening jacketed headers. Is this the right way to plumb the motor?

[SmokinLowriderSS]

Depending on how much engine you have, there may be 200, 300psi, or more coming thru that berk inlet line. The water is tapped from the pressure side of the pump, not actually from the suction. The least water flow is at idle with the most at WOT. The biggest problem is to reduce that pressure to an acceptable level for the engine seals to withstand.
Also, if the ID of that pipe is 3/8, it is nominally 1/2". Go to a hardware store sometime and actually compare to a piece of 3/8" steel pipe (not copper, the measurements are different). 3/8IPS(Iron Pipe Size) is some small stuff, 1/2"IPS has a lot more flow area.

[Duane HTP]

It is a 3/8" pipe, and it will give you more water than you need. More than likely you will have to restrict it a little. The offshore guys don't have the 200 to 300 lbs of water pressure available that you do. They have to pump their water in to their engines. Thus, the difference in line size. Read your PM.

[UBFJ #454]

Duane - What range of internal water pressure should a motor have ... From idle to WOT?

[SmokinLowriderSS]

I wouldn't want anything over about 20 psi. I think that is about the top end of sealed pressure capped automotive systems.