It will be fine. It should be rated API CJ-4, CI-4, CH-4, CG-4 and CF/SL which will be ok for what you are using it for. Once you run this and drain it, switch to a marine 40w which will take more fuel dilution and have better shear strength. But all fleet is a diesel oil and will take a pounding. For marine use lots of guys run diesel 15w40 or 40w Delo, Rotella or Delvac. Pennzoil also makes a Marine 40w that Walmart sells. I use 25w40 Quicksilver oil that has no viscosity index improvers that works well too. West Marine carries the whole range of Marine grade oils. They handle fuel dilution really well versus automotive brands.