Pontoon Boat & Deck Boat Forum

I bought my boat last year and it was only slightly used (a dealer's demo boat) and I have always been slightly concerned about the water pressure the gauge shows. At idle it displays 2-3 PSIG and at full throttle (5500 RPM) it displays about 7-9 PSIG. It has never given me any reason to think it's overheating and the engine's pee stream appears to be ok. Do I need to be concerned. I bought a new impeller and thinking about replacing it to see if anything changes, but it's only a 2008 model and I wouldn't think it would be bad already? Any suggestions?

I think your ok as mine shows around 10 WOT

I'll double check mine this weekend, but I believe it is around 5psi @ idle, and 20psi @ WOT.

I had similar pressure on my 90 4 stroke.... There was no water pressure specification listed in the owners manual so I asked the dealer and they said that was normal. The owners manual did say it was a presurized system so I wondered if that was correct and did some more checking and finally ordered a service manual from Mercury. The water pressure at WOT is supposed to be somewhere around 20 to 30 PSI as I remember.

In the service manual there are some details as to how the Mercury Smart Gauges hook up so I looked at the plumbing on my motor with the standard analog gauge and it was quite different. My gauge was hooked up to the line going to the pee hole. This line does not see water jacket pressure, it is a low pressure line. These motors have a pressurized water jacket in addition to the thermostat. Anyway, I argued with the dealer and finally got them to hook my water pressure gauge up to the same water pressure port as the smart gauges and amazingly the pressure is about 20 psi at WOT. I have about 10 psi at 3000 rpm and feel a whole lot better about it. They argued that the port was only for smart gauges and I argued that it doesn't matter what type of gauge it is. By the way, it does take a special water pressure fitting on the 4 stroke for that port.

I don't know if your Optimax is similar to the four stroke but I do know it also has a pressurized water jacket. Hope this give you some ideas to follow.

mine is at 10 psi, I did at one time had trouble because of a blockage in the thermostat that made the pressure rise to 25psi at full throttle and overheat the engine. I think you'll be ok