Twin 509`s .. I installed a Canton oil stat on the starboard motor.

Getting the oil lines under the motor using a mirror was a good time pfft! had some nice lines made up to connect everything and the results are only about 20* difference before and after.
Instead of 160* it`s about 175* or so never over 190*.
Its supposed to open at 220*

I feel the lines and its bypassing the oil cooler it seems.. so I`m confused is Lake Michigan just too cold?

Interesting. Everything routed correctly I am assuming.

I have a Canton on my boat, wont make any oil temp at idle speeds, once on plane it comes right up to 210F or so and stays there. I did have an issue where the oil temps were not getting high enough when cruising around late last fall, the water temp was really cold so i figured that the block cooling was cooling the oil as well.

I am running a warmed up vortec 350. I was considering running an oil cooler (don't currently have one) but wanted to check my oil temps first.

Running at 3000-3500 temp was 180-190. After a minute or so of wot, temp went to 205.

I boat in maine and the water is cold. If I put an oil cooler with a 220 degree stat, it wouldn't open unless maybe I ran it wide open for a long time, or maybe later in the summer when the water warms up.

So basically if I installed an oil cooler with a thermostat it wouldn't be used.

Your real oil temps have a lot to do with where and how you are measuring the oil temperature. If this is a stock engine and has stock mercruiser oil system I would leave it alone, quit fooling with it and go boating. "If it ain't broke, don't fix it".
Mercury has already done all the work for you, don't try and re-invent the wheel!

Best Regards,
Ray @ Raylar

I wish I had this problem..I have 502's with crane 731 cams and stock heads.. At 3000 rpm Mine read 235* at WOT they get 260*plus some.. I'm reading the temp right at the filter remote from a 3/8" bung right were the oil inters the filter.. I have huge oil coolers a teague oil adapter and stock 5/8 mercury oil lines, I also removed the bypass valves and pluged the outer hole in the filter pad, and I cant get my temps down for the life of me!!

If anybody has any suggestions please chime in!!!

Don't mean to hi jack your thread!!!

Where are you taking the temp readings???? Readings can vary 50* or more depending on where you take them. If you are not getting condensation in the oil, then the temps are getting high enough some place.

I think thats great advice, its the stock oil system and I`ve never seen moisture but my oil did get dark really quick. I`ll leave other motor as is, Lake Michigan is cold at this time.