260hp I/o expectations

[1224bret]

Id like to start off by saying im new to the forum and new to the v20. Seems to be quite a wealth of knowledge around here! I recently purchased a 1983 v20 with a 260hp I/o 350ci engine I've had quite a time getting all the bugs worked out of it. I finally had a chance to run it this evening and I'm wondering if its running at its full potential. I was kind of thinking it would run high 40s low 50s tonight best I could get was 38 mph on gps granted that was with a full tank of fuel and three adults in the boat. Rpm was around 4200 which seems about right. It sounded good though I know it has some old gas. Does my speed sound about right or should I be going faster? I'm thinking of trying a different prop something along the lines of a mirage. Right now it has a random aluminum prop on it and I can't seem to find the pitch on it. Any imput would be appreciated.