I have a Revolution Marine Oil cooler 3" x 18 that I bought used from a member on this form. The front part is the power steering and the rest is the oil cooler. I have #10 stainless steal braided line for all the oil lines. Temps are still reaching 300 degrees according to the gauge the sender is mounted in the block above the oil filter adaptor. I'm sure that it should lower than that with that size cooler. I think the oil cool might be clogged not sure I tried calling them but get no answer any info would be great thanks.

Don't play around buy a new oil cooler, check all plumbing lines. Make sure water line from the water pump goes right into cooler first then engine. Check gauges and sender as well. You should never run oil temp over 275.

Before you go nutty, get it up to temp and shoot the filter with a infrared gun. Make sure you're gauge/sender are telling a true story.

Secondly, make sure you're engine is not LEAN. If truly getting up to 300*, that's friggin hot.

ok thx ill check it out

is the 300 temp after a hard run or just up cruising around? if after a hard run does it drop down quickly? 300 is way too hot but as Mild said you need to shoot it to make sure it is a real number. most of the ones I have built and run would get up to around 230-240 on a hard run at WOT but as soon as you ease off they would drop to 200 or so within a minute or so.

just cruising it will get up to around 240 after awhile. At wot for a bit it hits 300 and it does come down back to 240 ish pretty quick. 300 is as high as my gauge goes not sure if its getting hotter than that.

also my engine temp is between 150 and 175 never gone past 175. not sure if that matter or not.

Definately !

Your block is a cooler, not just a heater. Temps on both sides try to equalize themselves.

Merc mainly uses 140F thermostats for many different reasons.

300F way too hot. Hope you have high quality synthetic in there now until you figure it out.

2nd that, my engine oil I thought was running hot, hit it with no touch heat gun , bingo : 30* cooler

I don't have a oil temp gauge. Does hitting a part of the engine with an infrared thermometer work?