Zero H2O pressure reading when running on muffs

[MExcelsior]

Quick question, my starboard drive is showing zero PSI H2O reading when running on muffs. Water is flowing great through the exhaust and the engine isn't overheating, but still wondering if the pressure from my garden hose is keeping the engine cool. My thought was that water cannot get through the pump unless it was running, but I could be wrong. Just want to make sure things are normal.

(My impeller is only 1 year old). Any thoughts...... Normally the H2O reading is low when on muffs, but it doesn't come off zero. The port is showing anywhere from .3 to .9 when I put at 1500 rpm. Usually in the lake, I believe the pressure is considerably higher.

Thanks in advance for your help.

 

[paulswagelock]

Just ran mine on the muffs this past week. .2 to .6 psi when on the muffs. I am thinking it was 2.6 or so when in the water just after I launched. All these were at idle rpm. Zero does not sound right, but maybe there was not quite enough flow from the hose to fully fill the pump and passages so you weren't reading anything. Odd that the sister motor under the same conditions showed pressure. Either repeat it and check it again with the hose on full flow, or put it in the water and check it asap before you run it much.