I bought an 1875 HF PolarKraft new in 2003 with a 60 4 stroke and it runs just fine. It gets up on plain just fine and will run between 36 to 40 GPS. The Grizzly you are wanting is a little bigger than mine I would think you get about 30 to 35 out of it. But it might do better than that. I would think the 60 4 stroke would work fine on the boat. A buddy of mine has a Grizzly that is bigger than my boat and he has a 50 2 stroke and it does just fine.
I know I like the fuel mileage I get with mine it does great there.
Good luck.
CX.