I range from about 260 to 310 and it has a deep oil pan and synthetic oil and a cooler it is a mild b and m blower I just bought this boat and if I keep it at full throttle for a 1 min it gets up to 310 at 5,500 rpm is that norm ? I don't know boats what should the averg temp be? and it has breathers on the valve covers with a little smoke coming from them no water in the oil thougth is that norm? Appreciate the help

Are you using the stock Merc oil cooler?310 is too high.My 540/871 runs 240.If you don't have one you need a 18" long x 3" cooler.

Where are you measuring? In any case 310 is too hot.

If its a gen 6 block make sure you have the 25 or 30 psi differential block bypass valves NOT the 5 psi automotive ones or all your hot oil may be bypassing the cooler,Smitty

I cleaned outmy oil cooler I do not have a filter system and it helped thanks

At 310 you are at high risk for an oil related engine failure. I would say 260 is the highest you should see. Temps in the 210-220 range are ideal. It could be that your oil cooler is too small or it could be running lean, detonating, wrong bypass, etc. We need more info on your set-up.

i'm haveing simular problems and i believe it has to do with the bypass articfriends is talking about. could someone tell us more about this bypass and where to find it and how to check, and change it out?? mine is a "1991" 502 truck block with the standard merc? relocate oil filter and cooler!!

Change your oil and keep it under 260* until you get it straight. Or you can fry that engine and do it right next time.