# Water Pressure



## Bruce J (Mar 4, 2018)

Thought I’d start a new post on this, but it’s a follow-on to my other one on compression plates, jack plates, etc...

I have a Maverick HPXT with an F70 motor. I show about 21-22 max water pressure up to about 3” on the jack plate. If I raise it to 4” it drops to about 15-17 psi. Any higher up and it drops off very rapidly. 

Does anyone know what a relatively safe but minimum pressure is for sustained running on plane, say 4-5000 rpm?


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## jay.bush1434 (Dec 27, 2014)

If the temp alarm goes off lower the motor or slow down. If not, your engine is happy. I'd be getting concerned around 10psi but again, if the motor isn't running hot, you still have plenty cooling water.


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## DONAGHUE (Nov 18, 2017)

Positive pressure is flow .... as long as u have flow u are good... anything above 2 psi and u are ok.... that motor has a fail safe on heat so u have plenty of safety factors to keep u in the green.... my take....


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## RunningOnEmpty (Jun 20, 2015)

I get real nervous about dropping water pressure. I tend to play it safe out of fear of damaging my power head. 15 psi is the lowest I run even though some consider 5 psi okay. I'm also interested to hear from others on this topic.


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## Smackdaddy53 (Dec 31, 2012)

DONAGHUE said:


> Positive pressure is flow .... as long as u have flow u are good... anything above 2 psi and u are ok.... that motor has a fail safe on heat so u have plenty of safety factors to keep u in the green.... my take....


You can have cooling passages and a water jacket covered in salt and scale and still have flow but burn up a powerhead because the crust creates a barrier between the aluminum and the coolant (water) and the cooling efficiency is lost.


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## Smackdaddy53 (Dec 31, 2012)

This is from personal experience. I bought a Maverick HPX Tunnel with a pristine 2001 Yamaha 70TLRZ 2 stroke and it ran great until the summer rolled around and the bay water temperature rose enough that the motor could not cool efficiently and would shut down on temperature all the time. I popped the water jacket cover and found this crusty mess that was killing my cooling efficiency. I got some StarBrite hull bottom cleaner in a spray bottle from Academy and a stainless brush and went to work cleaning it as well as the exhaust side coolant passages. Now I can run my motor sky high and only overheat when I really push it. My motor jacked all the way down is about as high as most people’s jacked all the way up. 
The next step is a nosecone pickup.


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## DONAGHUE (Nov 18, 2017)

Absolutely ..... flow is not gonna do much if the water isn't getting to where it needs to be.... I'm sure that buildup holds heat also.... dam sure doesn't help cool...


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## DONAGHUE (Nov 18, 2017)

I run my motors twice a year in a vat with vinegar/water hoping to prevent that mess... so far so good.... nice work on that cleanup.... looked like a major PITA but well worth it...


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