Mercruiser Says To Use Their Motor Oil Does It Matter , Does The Engine Last Longer Or Perform Better I Would Like To Hear From Some Other Boat Owners Before I Put Oil In My Fresh Rebuilt 7.4 Any Help Would Be Appericated Thanks James

Put in Regular mercruiser spec oil for the first 10 hrs then swithc to a good synthetic such as Mobile 1 or Amsoil or Valvoline.

Use Rotella to break it in for 10 hrs or so. Then switch to a high quality conventional oil or synthetic. I prefer Mobil 1 15-50.

I've been told that Mercruiser oil has additives that are designed to meet the challenges of the marine enviroment.Besides that , it is good oil ..meets or exeeds boating industry standards and they do have a synthetic if you intend to run Wide Open throttle all day.

Rotella 10+ hours, then switch. I have had great results with Mercruiser Synthetic blend 25W-40

I agree with the use of a regular oil for "break-in" period of the first couple of hours. But look at the top engine builders and see what they use. Royal Purple and Mobil-1, (both full synthetic) seem to be two top choices.

I use Mobile 1 15/50.
I have supercharged motors.

I used to use some royal purple 20w50 in my engines (525sc clones), and this oil is a very very good one.

But what do you think of the new verado oil it is a 20w50 synthetic blend, with some specials additives....??? someone already have tried it ???

I run Amsoil Dominator 10w-30 racing oil, it's designed for high load applications. I run on Lake Huron and it's 30 miles to get to the nearest anything and I run hard. On top of that at the start of boating season Lake Huron is 34 degrees, and late August the rivers are mid 70's. I can run hard on the Lake and then idle for a hour down the river and the oil pressure stays real constant.

"after break in" i run royal purple 20w 50 Raceing oil, not off the shelf royal purple and im very happy. it's $16.00 a quart but the inside of my blower motor look's and check's like new.