It's getting harder to find the 20W50 on the shelf lately. Any problems with going to the 15W50?

What mills? It has served me well for many years in my engines. Currently running it in a 496 MAG.

http://store.avlube.com/mob1vtwinair1.html

I used Mobil1 15/50 for years and so did the prior owner.

using olny 15 50 mobil 1 in two 800 blower motors .

300 hours 15/50 Mobil 1 in 454 mags, no problems.

Any luck breaking a motor in with Synthetic??

None that I know of. Boat had over 20 hours on it when I bought it from Majic Float. (It was Formula's photo shoot boat) I don't think yjey were running synthetic. I have 110 hours on it now and still running strong. I've been using 20w50 since new but it's getting harder to find. Change oil every 30-35 hours. I have no problem going to 15w50. Thx.

I've been running Mobil1 15w50 for 6 years in two boats. Its great stuff.

15W50 it is!!!!! Thanks.