quick prop quetion

[troypolla]

Im sure you guys can help me out on this one. I have an 18 foot CC that at WOT is in the proper range 5000-6000 on an 05 Yam 115. Top speed it about 36-39 depending on the amount of fuel, and people on board. With a loaded boat and a full tank of gas I can get to 5200-5300rpm with 5 people. My question is if I move from the Powertech 15 cupped up to a 17 with or without cup would I have hole shot problems not reaching WOT problems? or anything else that yall can think of. I already have a set of the Bennet sport tabs with the wings or whatever they are called. Let me know what you guys think about my options.

 

[Silvertip]

Re: quick prop quetion

What is your OBSERVED wide open throttle rpm with an average load? 5000 - 6000 is too broad -- you need to be more specific. Actual observed WOT rpm if propped correctly should be at or very near the top of the recommended rpm band (6000 in this case). Cupping adds roughly one inch of pitch over a non-pitched prop. In your case, while you are probably propped ok for average load with the 15P, you fall a little short with a heavier load, going to a 17P (cupped or not) will pull even more revs off WOT and yes, you will suffer hole shot. There simply is no free lunch here. The real unknown is changing prop pitch as well as prop manufacturers. A 17P prop from manufacturer "A" may not and generally does not perform the same as a 17P prop from manufacturer "B" or "C".

 

[Dhadley]

Re: quick prop quetion

If 5 people is your normal load and you're only getting 5200-5300, that's too low now. Going to more pitch will lower the rpm even more. With a 4 stroke you want to get as close to 6000 as possible.

Rather than spending money on a low technology prop I'd suggest playing with the set up with what you have now. Have you tried raising the motor?

 

[troypolla]

Re: quick prop quetion

I have not tried to move it up yet because it sits off the transom by about 1.5 inches. I think the motor is in the right place cause it will start sucking air once I get to about 4/5ths of the trim. My average load includes 2-3 people and some gear. When I had 5 on board it was the most loaded I have ever had it. Also full tank of gas (40gal.) With average load and average amount of fuel I can reach about 5700. On the same note with little fuel and just 2 people I can hit 6000. I think I may just be on the right prop now.

 

[BaileysBoat]

Re: quick prop quetion

Like Silvertip says "No free lunch". This boat is rated for 150 hp, correct? That's a lot of boat for 115. I don't think you could add any more pitch, as you are struggling a bit with a full load.

 

[Randybeall]

Re: quick prop quetion

You are describing an ideal prop situation. The only way to improve is to go to more blades and start from scratch with size and pitch. More blades can give better slip numbers if the prop is designed well enough. However,as was pointed out the boat is rated for a lot more horsepower, it is not going to get 'A LOT' better than where you are now with the horspower you have.