Water psi Big tube headers
 

Hey guys, how many of you run water restrictors in the rubber hose on the back of the headers where it dumps in to the tail pipe? I have TONS of Volume just alittle low on psi. I know merc even makes these. Just dont want steam pockets or the top of my headers to turn brown.

Thank you :thankyouthankyou:

Are you running that bad boy with a single stage pump??

Best Regards,
Ray @ Raylar

Thank u. Yes I am

Most of the good marine high performance blower engine builders generally use 2 or even sometimes 3 stage raw water pumps especially if you are also using a chiller. I would ask this question of some of the OSO expert builders here like Eddie Young, Cobra Power, Whipple,Haxby Speed, etc. and I think they will give you some true good info on this subject for your monster. You got a lot of heat under power there to get rid of don't get yourself caught short.

Best Regards,
Ray @ Raylar

You say you have tons of volume. That's what you want. Remember, pressure is merely a measure of restriction. You need volume to keep the engine cool. Are you having a temp issue? Do you just think you need more pressure even though you aren't having a temp issue?
Eddie

Zero temp issue just low psi. Like 4-5psi at 40-70MPH and 8-10psi at 80-130mph Just fear steam pockets. Or u think i am good and just run her. Motor temp 100-135degs

THank you

But you also need pressure to fill the cavities, high flow with no pressure won't do that.

Skydog: Be sure to get rid of any air that gets picked up through your water pickup and the cooling might get better.

Those pressure numbers don't seem horribly low and the cool running kind of indicates you might not have any problems at all. I guess I would just recommend checking the calibration of your pressure readings with possibly a manaul guage? Just a thought. As for steam pockets I am not sure how higher system pressure resolves that kind of condition even if you had that situation. Maybe Eddie or others can clarify that?

Best Regards,
Ray @ Raylar

Ty guys!!! Yea I am feeding my sea strainer with two water lines in. One is the nose cone on lower unit the 2nd is a very nice threw the Bottom of the boat both should be seeing soild water with little too zero air in the water.
Well I think I will just run and keep a eye on my headers for discoloured.
Thank u guys

Higher pressure won't necessarily eliminate the possibility of steam pockets. it could actually make them easier to form.THere propensity to form is mostly dependant on the angle of the engine. If it sits lower in the front or is neutral, then it could certainly form some pockets in the rear. If the engine is higher in the front,then the odds of pockets forming in it are slim.

THe easiest way to eliminate the possibility is to put a bleeder hose off of the rear of the intake. You can come out with 1/8" NPT fittings. Go to #4 (1/4") hose into a tee. You can then send one 1/4" hose to a dump that goes overboard. You could also dump it into the headers if you have a bung. The other option is to bring it up front to the thermostat housing and tie it in there.
I prefer to dump it overboard. You can put it on the side of the boat and use it for a verification that you're pumping water. It will keep water flowing at the rear of the engine and release any trapped air.

Your pressure isn't really that low. Do the bypass for piece of mind and you will be fine.
Eddie

Thank u so much killer info! :)

This is only my opinion.. I think you'd benefit from higher psi as result of more volume instead of from a restriction. I'd add at least one more stage to your raw water pump like Ray mentioned earlier. Air is a highly compressible medium, if you have an air pocket in a corner somewhere the higher water pressure would make the pocket smaller, the higher the pressure the smaller the pocket, or possibly force it through the system and out the exhaust. Running dumps off the back of the manifold is always a good idea but it will bleed off a bit more of your already low water psi. I'm not sure how you're set up right now but you could run the drive pick up through the intercooler with its own strainer and then use the other one to feed to the raw water pump. You should be able to adjust that thru hull pickup to get any pressure you want and ultimately have enough that you can use a bypass valve to control it on the top end. I like 10-15psi at cruise, and 20-25psi up top.

Right on wow thank u :) :)

I've got Merc single stage pumps in my 604 quad whipples. Pressure fed intercooler. Zero problems. 10-15 cruise, 25 up top. I think pressure relief at the back of the intake is necessary if you don't have a circulating pump. If you are worried about losing pressure route it to the front of the intake.