[QUOTE=hugo;212056]that sounds great, thanks for the input. i will definetly try and get my hands on one. i see you stayed with 17 on all three props . . . QUOTE]
My 4B PowerTech is a 15x15. I tried a 15x17 but could only turn it about 5200 at max load with my motor, which is about 165 hp at the prop. The 15P turns 5450 which is right at optimum for my motor, and it turns that speed pretty much regardless of load in the boat. It runs about 5% slip at cruise, which is pretty good. In general, you'll probably want to drop a couple inches in pitch going to a 4B because of the increased blade area. A 4B will cost you a couple of mph in top end due to drag of the extra blade, but they're typically more efficient with lower slip numbers at cruise, and of course they're smoother. I think a 5B is overkill and would be hurt by additional blade drag.
I think the Merc Enertia is a pretty good 4B prop for your motor, although I think the Michigan & PowerTech props have a more robust 2-piece hub system. All the prop web sites have a prop calculator where you plug in all relevant boat info and what rpm you turn with current prop and it'll recommend a size. Ken at PropGods over in Tampa is another good source for props and info.
In general with a stainless prop if it's not the perfect size, I think it's best to have too little pitch than too much because a good prop shop can always add more cup to the blades, but it's pretty hard to remove it. When testing props, it's best to test with the heaviest load you think you'll normally run; fill some coolers with sea water for ballast if necessary to simulate max load. I think most folks don't do that and end up with too much pitch as a result. As Fr. Frank (who probably knows props better than anyone on the CSC forum) says, you want to prop for max rpm at max load. (or optimum rpm if you can find out what it is. E-Tec is the only manufacturer I know of that publishes the OPTIMUM rpm range in addition to the "recommended operating range", which is the only number most dealers seem to know about. The "recommended operating range" for my 150 is 5000-6000, but OPTIMUM range is 5400-5500.)
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