So my port side motor always runs around 165-170 cruising around and normal usuage, but when I run it hard it goes up to 185-190 range. This motor also steams out of the exhaust always and it diesels on shut off sometimes.

And what have you checked?

check the timing if its dieseling, will cause it to run hotter, do you have water flow not just pressure,

if it is jetted to lean it will cause a lot of heat,that and retarted timing may be the issue.what is the total timing?

I will check the timing. I don't have water pressure gauges so not sure on that. Sea water pump is brand new and did the same thing with the last seawater pump. I did have the seawater pump fail in less than a year on that motor but it was a sea choice or some knock off instead of a mercury. I wondering if there's a restriction someplace.

maybe not a bad idea to install transparent hose between steering cooler and thermostat housing to see if any air bubles in the system