OB17 vs FS17

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byboatbuilder
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Re: OB17 vs FS17

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Installed the new tach today and took her out to confirm that it was,in fact, the tach that had been giving me readings that made no sense based based on the way the engine was performing. My new Suzuki DF30A is rated at a max 6200 RPMS and with the boat fully loaded today with two adults and gear at WOT I was showing 5600 RPMS with a boat speed of 24.6 MPH. My guess is with one less person on board I would be close to maximizing the rated RPMS and probably gain a few more MPH. If some of you prop experts have some thoughts, please let me know since I am planning to purchase a stainless prop in the near future.

As always, thanks again for the helpful input that this forum provides

TomW1
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Re: OB17 vs FS17

Post by TomW1 »

What prop do you have on now, diameter and pitch. 5600 rpms with that load is not bad at all! It might be improved a little bit when you go to the stainless. I would like to see you set the rpm's with you aboard at about 6000 with the stainless. Then when you load it up your motor will not be over loaded. Remember a stainless is more efficient over an aluminum but we need to take into account the amount of rake and cup that the stainless has. I normally work with Power Tech props now, have not had good luck with some of the other vendors.

I will be glad to help you tune in your prop on your boat using my prop formulas..

Tom
Last edited by TomW1 on Fri Sep 09, 2016 8:15 pm, edited 1 time in total.
Restored Mirror Dinghy, Bought OD18 built by CL, Westlawn School of Yacht Design courses. LT US Navy 1970-1978

byboatbuilder
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Re: OB17 vs FS17

Post by byboatbuilder »

The prop that is on now came with the engine 10.5 X 12". Any help will certainly be appreciated.

Fuzz
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Re: OB17 vs FS17

Post by Fuzz »

Any way you cut it that is really good speed out of 30HP. Must be both a really good design and a boat built right 8) And it does not hurt it really looks good too :wink:

TomW1
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Re: OB17 vs FS17

Post by TomW1 »

byboatbuilder wrote:The prop that is on now came with the engine 10.5 X 12". Any help will certainly be appreciated.
Looking at the Power Tech props the SRA-3 in a 10 pitch may work very well for you. It has 20 degrees of rake and is cupped, so it will help you in turns and also allow you to raise your motor an inch or two. The other Power Tech props really don't provide much advantage over your current aluminum one. You would be as well off getting a stainless steel from your Suzuki dealer.

As Fuzz said you won't get much more speed, maybe a couple of mph but don't count on it with the load you had.

Hope this helps.
Restored Mirror Dinghy, Bought OD18 built by CL, Westlawn School of Yacht Design courses. LT US Navy 1970-1978

byboatbuilder
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Re: OB17 vs FS17

Post by byboatbuilder »

Thanks Tom for you helpful advice as I shop for an additional prop. The physics of your recommendation makes sense to me.

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remedy32
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Re: OB17 vs FS17

Post by remedy32 »

I went through much of the same stuff setting up my FS17 with it's little Yamaha 25 2-stroke. Another thing I found was that engine height had a big effect on top speed. 1/2" lifting raised speed by nearly 2 mph as I recall. But it was a back and forth between speed and prop ventilation. I still need to lower the current Yamaha 40 a bit to keep the prop better engaged when turning at speed. Looks like you are well on the way to sorting it all out.

When you get this fully sorted out I hope you'll post the results to my Aug. 2012 post "FS17 Performance". With a little luck others might be able to save some of the fiddling that we've gone through.

Bill
CT

byboatbuilder
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Re: OB17 vs FS17

Post by byboatbuilder »

I absolutely love this boat and will be more than happy to share my experience as I fine tune the engine position, prop and anything else that may be helpful to the future builders of the FS 17.

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