I have a 2001 271 fastec with a 502 mag.When running at 40 mph and above for 20 min or so the oil temp climes to 230 and will go at times as high as 310 which turns on light and warning chime .The pevious owner repoorted this to the selling dealer and they went to formula and they state this is not abnormal for this boat with these gauges .Im not buying that .It has merc marine 25w40 oil .Water temp runs at 170 at idle or wot. oil pressure is spot on .I feel I should run around 210 tops ? water temp of lake is 68 degres .I have cked the oil cooler for blockage and all so flushed it .Will seinthetic help ? p.s. the boat only has 125 hrs. on it

310* is too high. You want consistent oil temps at cruise speeds to run over 212* to burn off condensation.

You need to get an infrared reading with a temp gun of the oil temp in the pan.

I have installed larger oil coolers on several 502 MPI's. The stock cooler is not quite big enough. A 3" cooler will solve your problems. I have had it lower the oil temp over 80 deg. in some boats. Conventional oil is breaking down at that temp. Synthetics don't break down until about 400 deg., so you may want to switch until you can have a bigger cooler installed. Hope this helps, Eddie.

The stock oil cooler is pretty small,buy a bigger one and never look back. You could also replace your oil relief valves in the block,they may be opening or hung open allowing oil to bypass the cooler and filter,Smitty

artic is very smart on this issue. I had oil temp problems in the past and I bought the big hardin cooler with a thermostat. Without the different bypass valve, it only dropped the oil about 10 degrees. The synthetic mobil dropped it a little more and it was tolerable, but the bypass valve was more important in my book rather than the cooler. I would take a infra red temp other places. There are alot of stock 502's with a stock cooler without issues. Search in the forum and you will find endlass threads on this subject. Good luck. Dan

although i have little experience with this issue on 502's, i have spoken with reps. on the mercury technician help line in deatial about this issue on 496 applications. they have told me that oil temps of 250 or greater are commpon and pose no threat to the motor or any related system. - from the horses mouth....