I agree with Insurance man on the HPDI, they are very fuel sensitive. Had one on my basscat and seemed like was having problems all the time, and I ran nothing less 100% 89 fuel n it. My mechanic changed out the water separator, and put another big fuel filter inline and never had another problem. Had a Mercury on my Phoenix and never had a problem out of it,think the fuel mileage was way better than the HPDI. My next boat will be powered by Mercury, think more confidence in it over the HPDI.

Both engines are good, even Gen 1 HPDIs which I have now without a problem. Had a friend lose his #2 cylinder a couple of weekends ago on a 3 years old Pro XS. My coils fried on my 08 Pro XS. It's about motor maintenance, and how you care for the engine. EVERY TIME you run your boat make sure you: warm your engine for at least 10 minutes IN GEAR(idling only runs 4 cylinders), use fuel additives(I use ring free+ and marine stabil) on every drip of gas, and preferably use ethanol free fuel, but if that's not an option find a station that sells a lot of fuel so you know it's fresh, and lastly don't hammer the engine every time you're running it. No engine is designed to be run at 6k rpms all the time. You'd blow a car's engine redlining it every time you ran it.

I have a 2006 HPDI with 350 hours on it and I run it hard and not one issue. It must depend on the motor. We were down in Destin a few weeks ago and there were HPDIs all over the place so I have trouble believing they are all that awful.

Get it serviced regularly whatever brand you choose.