Read as many oil posts as I could before asking these questions.

Previous owner used Royal purple 10W–30 HPS in motors, motors have about 1560 hours each. Probably a good idea because of the higher zinc content in the HPS but I think the 30 weight in our hot summers is a little thin. Boat would never run below 45 degrees F. I have pretty much decided to go with Rotella 15w-40 just not sure which one. The GEN set calls for 10 W – 30 when any temperature is below 50°. He gave me about 7 quarts of the Royal purple, may use that in genset, the Kohler oil specified for this advertises added zinc so assuming these are flat tappets. Generator only has 322 hours. Not sure what oil is in it now, was done by local service shop. No record of what oil.

Anyone see a problem with either one of these oils for the described? Also anyone have recent numbers as to the zinc and phosphorus content of the different Rotella oils. Hopefully they’re all above about 1200 which should be fine for these motors I believe.

Thanks