My oil temp is running between 140 and 150.. What are the pros and cons of running this cool.. I have heard that you can damage your engine or loose HP if it runs to cool..

That's really low. You will not burn off any of the water/condensation that WILL be in your oil (part of boating.....unavoidable). You need to be able to get 200+ degrees when you run it at WOT to burn off the water. And yes, it's probably robbing a bit of hp too......but probably not enough to notice.

What boat are you running......what motor......what hp????? How many rpm???

My engine is a 1999 HP500 carb. It also does have a crossover. I don't know if it has a thermostat....

Mercruiser supplies an oil thermostat on all blue motors.

Maybe something is stuck in the t-stat.

Or, if there is a crossover, maybe somebody has changed the plumbing around incorrectly (HP500s dont come with crossovers)

I had the same problem after a crossover install, Keith eickert oild themostat is the answer quick heat up and a constant 215 degrees

Did you try another sender for the oil pressure temp? Maybe yours is shot? Just trying to help, if I'm way off sorry

removing the recirculating pump and replacing it
with a cross over set up on a engine already equipped
with a oil cooler thermostat (like the "blue motors")
shouldn't change oil temp
water still flows from the sea pump outlet, thru
oil cooler, the to either the water dist. block on
the intake manifold, (stock) or the inlet to the
crossover.
on merc's setup, oil is not allowed to flow
thru the oil cooler til thermostat opens ( approx 200*)
the oil cooler thermostat is located in the oil filter
housing, there is a plug with a snap ring holding it in,
remove the snap ring, return spring should push out
the plug, the thermostat is now accessable,
check to see if the return sping is broken,
or if the thermostat "push rod" is extended, or
stuck in the open position.
this would allow oil to flow thru the cooler at all times,
oil temp should still come up after "long, hard runs"
though.