I'm trying to figure out what would cause high oil pressure? it idles around 60psi and goes up to 90 psi when i get on it. This happened after I got the boat back from having a large stereo/inverter installed and a few of my gauges do flicker and act up, however i think the high oil pressure is correct be cause i can see oil being pushed up the clear oil tube that injects into the flame arrestor.

Any thoughts on where to start?

Im assuming it has changed from what it was? Is it an electric gauge? If it is i would try putting a mechanical gauge on it and see if somehow when they wired up your stereo it jacked up something with your gauges.