Prop Confusion...

[cordell]

Hello, I was at the river this weekend and my prop hit a rock, BAM! It is beat up beyond repair I pulled it off today to try and order a new one and this is where it gets confusing. By the bearing it has the numbers A625265 and PS625. I googled these numbers and nothing. On the side of the prop it reads 13 <RP> 17, though the 7 looks to be stamped over another number like someone machined the prop down to a 17. I looked at the prop a little more and found 19 stamped on it smaller and upside-down in relation the the other stamping. Is it possible to re-machine a prop down in pitch? I need a new prop but would hate to buy one that is not the one I need/want. I am OK with current performance, I wouldnt mind RPMs being higher unless it slowed me down. Slower is not good, lol. I get out of the hole pretty good, I also have a hydrofoil/whale tail on the motor. Any help, advice will be appreciated. The boat is a 1990 Bayliner Capri Bow Rider. It is rated at 90 HP and I have a 1987 Force 85 HP on it. Loaded down with fuel myself, wife, and 2 small kids I hit 4700 RPM at WOT and 30 MPH on a good day.

Thanks
cordell

 

[thompy]

Re: Prop Confusion...

as far as i know you can only work 1 pitch up or down and your rpm sounds a little low like it was over propped, does your motor have a tag with proper operating range under the cowl, my 140 Chrysler is 5000-5500, on its tag

 

[cordell]

Re: Prop Confusion...

as far as i know you can only work 1 pitch up or down and your rpm sounds a little low like it was over propped, does your motor have a tag with proper operating range under the cowl, my 140 Chrysler is 5000-5500, on its tag

My motor manual states WOT to be at 5500. I have tried to adjust throttle cable and it is maxed out. If I am/was a bit over propped I go down in pitch correct? And by doing this RPM should go up closer to WOT range, should speed increase with this as well or would I lose some MPH? Would it help if I upload a pic of the stamping on my damaged prop?

thanks
cordell

 

[Silvertip]

Re: Prop Confusion...

When going down in pitch, rpm goes up because the prop takes less bite therefore it must turn more RPM to maintain the SAME speed you had before. The opposite is true when going up in pitch. Speed does not necesarily decrease or increase unless the engine was being severly over or under propped with the original prop.

 

[cordell]

Re: Prop Confusion...

When going down in pitch, rpm goes up because the prop takes less bite therefore it must turn more RPM to maintain the SAME speed you had before. The opposite is true when going up in pitch. Speed does not necesarily decrease or increase unless the engine was being severly over or under propped with the original prop.

I see. I got a hold of a 15 pitch prop today. It has 15 C stamped on it. I am guessing 15 is pitch and the C is Cupped. I am going to take a little run with it and see what happens. If RPMs go up but speed drops I need a higher number pitch, correct. I was fine with the prop I had I just dont know if it was a 17 or 19 as BOTH numbers are stamped on it. I will report findings tomorrow...

thanks for all the help everyone
cordell

 

[cordell]

Re: Prop Confusion...

All prop logic I have read, been told is out the window. I went out today with a prop that has 15 C stamped on it. I was by myself, half tank, got to 30 MPH at 4050 RPMs. My prior prop was stamped 17 I also ran about 30 MPH but RPMs were 4800. Why did a lower pitch drop my RPMs rather than raise them? All logic is gone, no? What should I do now, I want RPMs back up, speed is the same so I did not lose anything but RPMs. Is running 1800 RPMs below recommended WOT bad for my motor? Please give me some incite here as I am 100 times for confused than I was when I started this thread!

thanks
cordell