2010 F200 124hrs / Pressure relief valve?

[YamahaF200]

the water pressure guage on my console reads 15psi when i start getting under way and up to the point where the boat get's up to plain and cruises (at any RPM) momentarily, then it fall's to 11psi. the P stream seems to ok, no significant change in volume. i'm pretty certain that the pressure used to stay at 15psi.
is this drop in psi related to the pressure relief valve? or a water pump impeller? which was recently changed out at 115hrs?

thx in advance for any input my friends

 

[YamahaF200]

Re: 2010 F200 124hrs / Pressure relief valve?

i have a Yamaha Mechanic coming over Friday to show me how to replace my the timing belt on my LF200. so i'll ask him what he think's about the symptom. i did drop the lower unit and inspected the impeller and housing for any defects,...look's like when i installed it several month's ago