Whats enough water pressure??

[blender over]

i got a 225 merc w/a sprotmaster lower unit, on a tunnel boat.
Wanting to jack my motor up level with my center pad, just wondering how much water pressure will i need to stay safe??

[Tom Brown]

Don't let it go below 15 lbs, or so, at 5500 RPM. It will probably be higher than that when everything is running right. If you jack too high and suck air, it will drop off sharply.

[blender over]

Don't let it go below 15 lbs, or so, at 5500 RPM. It will probably be higher than that when everything is running right. If you jack too high and suck air, it will drop off sharply.
thanks :)

[Towndrunk]

I have never had more than 5-7 psi at wot. I keep hearing about 15 plus but I've never seen it. Never had a motor go because of lack of water.

[timebomb1]

I have seen 25 psi with the sportmaster gear case and an external pickup. Now that I have had the tuner drystacked I never see over 18. Gary

[MONEYFURNOTHIN]

Merc recomends not less than 12 at w.o.t.

[dreamboater]

I have run as low as 7 at WOT with 300 promax's and sportmaster lowers. For safety reasons I would keep it around 10-12 for everyday running.

[votech]

i don't think mine ever gets to 12 it stays around 9/10 jacked up or not. 225 merc and stock lower/pick ups

[HavasuDreamin']

i don't think mine ever gets to 12 it stays around 9/10 jacked up or not. 225 merc and stock lower/pick ups
How is your water impeller? You should be able to get more.....you need more.

[spectras only]

Don't have a outboard , but two sterndrives with smartcraft gauges. Both gauges show 12 lbs max at WOT.

[votech]

i think i put in a new impeller last winter ,so i'm prob ready to replace it . plus i didn't have a guage till now , it does't over heat or get hot now might go up alittle w/new impeller ?

[h2oski2fast]

I have never had more than 5-7 psi at wot. I keep hearing about 15 plus but I've never seen it. Never had a motor go because of lack of water.
No one mentioned have a thermostat or restricters installed. If not then you will see low water pressure. The max I get is 5-7 lbs.

[spectras only]

I have thermostats , and water pressure is less than 1 while the T-stat is closed.

[Tom Brown]

No one mentioned have a thermostat or restricters installed. If not then you will see low water pressure. The max I get is 5-7 lbs.
Low water pressure won't necessarily cause an alarm unless it's really bad but it will cause flash insulation in the water jacket around the cylinders. You need the pressure to keep the water in liquid form at that temperature.
Sure... it will run with low pressure but your cylinders will go out of round over time and your engine will lose a little power. Merc specs that pressure for a reason.

[sorry dog]

Mercury sucks.