Posts: 3480
Location: Elk River, Minnesota | Hiya,
First thing I would be looking at is the pole setting on the tach. If it is only reaching 3000 but you are seeing 28 to 30 mph, the motor is definitely at a higher rpm than what the tach is reading.
That boat weights about 900 pounds, so the speed you are seeing is relatively close overall...maybe should be seeing 32 or so, but much of that as some have stated could be more of a prop related issue.
I would definitely start there with a lower pitch to see how things perform. A 4 blade as mentioned as well is definitely a good thought, although with the weight of the boat, I think you might be decent with a 3 blade.
In a general sense, going down in pitch (keeping same # of blades and diameter) you generally see a change of 200 rpm for every inch of pitch you change...in your situation, an increase. But...if you tie on another blade, the rpm increase you will see will be reduced some..probably to the tune of 100 RPM give or take. I honestly don't think you are going to be too far off the mark overall, but I could see that when you get 3 guys, all of their stuff, a full livewell, full gas tank, etc. a lower pitch just for that might be in order... That's a lot of extra weight...especially if the guys carry a little extra poundage themselves... 
So...First thing I would consider is the Tach...ensure your pole setting is correct, then consider the prop. An accurate tach reading is essential to properly setting up prop to rig.
Steve |
