Prop question

[JasonJ]

I pulled my boat out of the water yesterday and started doing some maintenance. I pulled my prop off toclean and regrease the shaft and was looking at the prop and then pulled my spare prop and noticed they were different. the prop I have been running is 13 diameter by 17 pitch, but the spare is 14 diameter by 17 pitch. Also, there were 1/4 inch holes drilled near the base of the blades on the 14x17 prop. I decided to put it on just to see what will happen when I take the boat out again. What can I expect to see? The engine (125 horse Merc I6) tachs near 6000 rpms with just me in it. Will I get a better bite, go faster, go slower? Also, what are the holes for? I have heard of them, are they some sort of exhaust relief?

 

[Dhadley]

Re: Prop question

Are they both the same brand? Both stainless?

 

[JasonJ]

Re: Prop question

They are both aluminum Michigan Wheels.

 

[The Marine Doctor]

Re: Prop question

The vented prop should give you better response off the bottom end. Its hard to say about the top end though..as the vents no longer function.<br /><br />TMD

 

[JasonJ]

Re: Prop question

Thanx guys, I may take it out this weekend and see. Gives me an excuse to take it out....

 

[ob]

Re: Prop question

I'm guessing with the wider diameter of the 14X17 that you will see lower WOT rpms.1" is a big jump.

 

[JasonJ]

Re: Prop question

So I got off early today, and instead of getting firewood, I decided to take the boat out and check that other prop out. I don't have power tilt and trim, so I left it where it was set for the other prop, and it did get up and go hole shot wise, but at full throttle it was bow steering and my rpms dropped to about 5100 rpms. I tilted the motor one hole farther out, and that made all the difference. My rpms went back up to about 5800-5900, and I was definatly faster. I have given up on my pitot speedo. I now stay even with traffic on the Long Bridge, a bridge that is over a mile long, and its speed limit is 55 mph, but the stupid pitot speedo says 35 mph. I need to borrow, buy, or recieve as a gift a GPS. I am working on that. It is the only way I'll know for sure. Soooo, in conclusion, the 14x17 works better than the 13x17. It makes me wonder, since I am hitting high 5000s, if I shouldn't go up a notch in pitch, or just leave it, thankfull that it goes pretty darn fast, and I have some breathing room for extra weight....