Optimum Water PSI
#12
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Location: Okanagan Falls BC. Canada
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On my Merc 6.2 engines the water pressure sending unit is screwed into the power steering cooler, after the seawater pump, so I assume that's a good location for sending volume info regarding impeller condition. An additional water sensor is in the thermostat housing, they all tied in with the SmartCraft system. I have a hard line plumbed in the themostat housing as a backup, both, Smartcraft and mechanical gauges read the same exact pressures.Location marked in the picture.
#13
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Previous boat had a 496HO and at idle it was around 3psi, on the hose, slightly higher when in the water.
#14
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Dave, forum member motor's estimated pressure readings at idle is correct. The MPI Merc engines run at a very low [ 600 ] rpm, so there's volume but not much pressure buildup after the seawater pump. Your raise rpm to a 1000 and you'll have instant pressure readings on the gauge. WOT pressures up to 25-30 PSI depending on impeller condition is good. Pressure in the block will be slightly lower [ Bernulli's princpial ] actually because of the thermostat passage restriction but velocity will be increased into the block. 20-25 psi readings on the SmartCraft @WOT, it's all good.Reading pressures with hose on isn't accurate because of the utility pressure way too high, allowing bypass pressure added through the impeller vanes.
Last edited by spectras only; 05-29-2014 at 04:02 PM.
#15
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Dave, forum member motor's estimated pressure readings at idle is correct. The MPI Merc engines run at a very low [ 600 ] rpm, so there's volume but not much pressure buildup after the seawater pump. Your raise rpm to a 1000 and you'll have instant pressure readings on the gauge. WOT pressures up to 25-30 PSI depending on impeller condition is good. Pressure in the block will be slightly lower [ Bernulli's princpial ] actually because of the thermostat passage restriction but velocity will be increased into the block. 20-25 psi readings on the SmartCraft @WOT, it's all good.Reading pressures with hose on isn't accurate because of the utility pressure way too high, allowing bypass pressure added through the impeller vanes.
I think most importantly, I look for consistent readings.