Hi
The gear ratio would be good to know, along with speed and rpm as mentioned but...
If it's any help to you, I have the same basic engine in a 18ft bow rider at 1250kgs. I also was curious to know what the original prop was, after purchase and finding the prop that was fitted was too small.
I wrote to the manufacturer to find out. They should be able to tell you.
What I can tell you is that a standard version of my boat has the following specs, which you could use as a rough guide;
Weight-2886 lbs
Engine-5.0 mpi 260hp
Gear ratio-1.47
Length-18ft
Propeller standard form is a 14x19"P black max.
If your boat has the same gear ratio, I'd imagine a 20" might be slightly over propped, given the extra weight ?
That said, with the standard 19"p Ali prop, my boat would easily hit the limiter, with the wee extra tweaks the engine has.
For all round useability I now have a 13 3/4x19"P laser 2 stainless. It suits the boat well, as long as I don't let her run flat out and trimmed up. She will touch the limiter on occasion then.
I'd imagine the same prop wouldn't be a million miles away, with regards to your boat ?
Just as long as you are within the 4600-5000 rpm rev range which it should be in.
You may even find a 17"p stainless would be well suited, depending on your use and load onboard.
Sorry for the chapter and verse, but hopefully this will give you a decent comparison.
