Full disclosure - I am no expert on props, but for what it’s worth I just repowered my 78’ inboard with a crusader - 330 HP same transmission as yours. When the mechanic took it for a sea trial he was doing 35 knots at 5000 rpm’s, 26-27 knots at 3500 rpm’s. I have a 16x16 Nibral prop.
This was on an empty boat with 30 gallons of fuel and 2 guys on it. WOT is 5200 rpm’s for my engine, but I am happy with the cruise - 5 knots faster than my old engine, but that’s with an empty boat. I may need to go to a 16x15 prop, not sure yet. As I said I am no expert, but reading all the posts on this site about it - seems you have to do some trial and error, but maybe the 16x16 or 16x15 gives you a starting point. I am sure you will get a lot of feedback. Lots of very knowledgeable people on this site. Good luck with the repower!
|