I have a 95 Nordic 28 heat with an engine oil temp gauge. Running a 468 bbc and the engine oil is around 300* (give or take 10* Is this normal? The engine temp stays right around 160*

Way too hot. Should be around 180*-190*. Check by pointing an infra-red temp gun at the oil pan.

engine oil ???? don't think so....thats a little to high..depends on what you have been doing running hard for long time....mine would get to to about 280 after running hard..did find the wrong 11psi valve in the block(gen VI) they say that will make a big diff putting the 30psi one

Which valve are you talking about. I have gen 6 502's and tend to run a lot of oil temp. Have heard about this problem but never in specifics.

I was told to never let it exceed 240 to keep things safe.

The Mercury 525 service manual puts the max at 220* so I would start to get concerned about that temperature. I don't know anything about a pressure valve but it sounds like the oil cooler is not working. Do you have an oil thermostat? Could the oil cooler be plugged?

Do a search on oil bypass valve, you'll get a lot of hits. Around 95 is when they were having problems with them. 300 is into the danger zone.

Also make sure you have an oil cooler. As crazy as this sounds I have seen some boats with them by passed or oil filters on the motor.

Gen IV block, 468, not run that hard 4200rpm for about 30 min, It is in a 95 nordic 28 heat. Oil filter is on the motor. It has the bolton/spinon oil filter adapter. I have an oil cooler mounted on the stringer that the sea pump flows through first before going to the block. It gets feed from 2 lines dirrectly above the filter. No oil thermostat. Just added the oil temp gauge with the sending unit in the bottom of the pan. Also it is a dooley 14qt oil pan.