GF16 in FL

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94'325is
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Re: GF16 in FL

Post by 94'325is » Tue Jan 24, 2017 1:37 pm

TomW1 wrote:
Tue Jan 24, 2017 1:28 pm
If you want some help in determining your prop pitch let me know and I'll run it through my prop calculators.

Tom
That's a really nice offer and I plan on taking you up on it, thanks!



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Re: GF16 in FL

Post by TomW1 » Tue Jan 24, 2017 8:39 pm

Rollbar I have my own calculators. They are pretty accurate and can get most boats right on or to within one pitch of what is needed. You always want to have the ability to exchange the prop that you buy the first time so that you can get it right. Right now I recommend Power Tech they have a wide variety of pitches and cupping in all sizes from 9.9HP to 300HP. For example they have 7 props for a 20hp motor. You can go to ptprop.com to look at them.

For recommendations please contact Cracker Larry 2 boats or Jacques.

If you want to do it your self you can buy David Gerr's book on Amazon, I don't remember the exact title but it is Propeller HandBook I believe but search by Gerr and you'll find it.

I did have one failure in that I and the person I was working with were not on the same wave length. I thought he wanted max speed and he wanted better hole shot. So he ended up getting a lower pitch prop on his own. Lack of communication, haven't let that happen again. I will ask lots of questions and may call you to clarify what you are using the boat for and to clarify anything that is not clear on the forum.

Tom
Last edited by TomW1 on Tue Jan 24, 2017 9:00 pm, edited 1 time in total.
Restored Mirror Dinghy, Bought OD18 built by CL, Westlawn School of Yacht Design courses.

Rollbar
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Re: GF16 in FL

Post by Rollbar » Tue Jan 24, 2017 8:56 pm

TomW1 wrote:
Tue Jan 24, 2017 8:39 pm
Rollbar I have my own calculators. They are pretty accurate and can get most boats right on or to within one pitch of what is needed. You always want to have the ability to exchange the prop that you buy the first time so that you can get it right. Right now I recommend Power Tech they have a wide variety of pitches and cupping in all sizes from 9.9HP to 300HP. For example they have 7 props for a 20hp motor. You can go to ptprop.com to look at them.

For recommendations please contact Cracker Larry 2 boats or Jacques.

If you want to do it your self you can buy Richard Gerr's book on Amazon, I don't remember the exact title but it is Propeller Dynamics but search by Gerr and you'll find it.

I did have one failure in that I and the person I was working with were not on the same wave length. I thought he wanted max speed and he wanted better hole shot. So he ended up getting a lower pitch prop on his own. Lack of communication, haven't let that happen again. I will ask lots of questions and may call you to clarify what you are using the boat for and to clarify anything that is not clear on the forum.

Tom
Thank you.

Found a link for Amazon in case someone needs it.

Link: https://www.amazon.com/exec/obidos/ASIN ... tdesignnet

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Re: GF16 in FL

Post by TomW1 » Tue Jan 24, 2017 10:23 pm

94'325is wrote:
Tue Jan 24, 2017 1:37 pm
TomW1 wrote:
Tue Jan 24, 2017 1:28 pm
If you want some help in determining your prop pitch let me know and I'll run it through my prop calculators.

Tom
That's a really nice offer and I plan on taking you up on it, thanks!
Make sure you have a tachometer of some kind to dial in the prop. Tini-tachs at about 50 bucks work well on small boats, tinitach.com. Your Suzuki 20 has a max rpm range of 5300-6300 rpms. We want to get a prop that gets it running above 6000. Thus the need for the tach.

With the Power Tech props there are 7 props we have to choose from if the standard Suzuki 9.25x10 doesn't work out. Don't know if that comes with the motor or not if not don't buy it and we'll do the calcs and see what should work best. Another problem with the Suzuki props is they only come in 7-11 pitches. With a boat as light as GF16 we may need something a little more.
Restored Mirror Dinghy, Bought OD18 built by CL, Westlawn School of Yacht Design courses.

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Re: GF16 in FL

Post by Rollbar » Tue Jan 24, 2017 10:30 pm

If you get the TinyTach MAKE SURE you buy the TT2A and the selection button to 360 for most motors.
OR,
You can buy a GMR pick-up and use a regular analog tach.

Note: TinyTach bounces/fluctuates since it is digital.

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Re: GF16 in FL

Post by TomW1 » Tue Jan 24, 2017 10:52 pm

Yes the TT2A is for gasoline motors, sorry I didn't specify that in my earlier post.
Restored Mirror Dinghy, Bought OD18 built by CL, Westlawn School of Yacht Design courses.

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Re: GF16 in FL

Post by 94'325is » Wed Jan 25, 2017 7:45 am

Got the transom bulkeads cut and glassed into place, used leftover 1/2" ply. The plans don't call for them but it serves me 2 purposes; 1. stiffen the transom even more and 2. give me extra storage. I'm planning on filling the outside compartments with foam and the middle will be open to allow for water to drain. I have 2 gallons of pourable foam so what that doesn't fill all the way I'll make a shallow storage compartment for tools/smaller items.

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94'325is
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Re: GF16 in FL

Post by 94'325is » Wed Jan 25, 2017 7:51 am

I bought this one already, I haven't tried it yet since I haven't fired the engine yet but my Dad has used this on similar smaller 4 stroke 2 cyl engines and has had good luck: https://www.amazon.com/dp/B0049IFX56/re ... uybG8HH989

Also this is the prop listed as the what comes with the engine, I haven't looked at it yet but will check tonight: 3-Blade Aluminum 9.25" Dia x 10" Pitch

Seems like it would need more pitch out of the gate, but it will be interesting to see what the real numbers are once it's out on the water. Since the engine is brand new, I'm thinking it will need to be broken in before figuring out what the maximum RPMs are but I'm concerned with running the factory prop and not being able to get to full throttle/bouncing off the limiter during break in. I'm wondering if it would be better to estimate the correct pitch and run that out of the gate and fine tune from there.

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Re: GF16 in FL

Post by jacquesmm » Wed Jan 25, 2017 9:55 am

We have exactly that same engine on my son's GF16 and it feels under propped.
We are still in the break in period, no figures and anyway, I don't care about 1 or 2 extra miles at top speed but if I buy a spare prop, it will have a little more pitch.
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Re: GF16 in FL

Post by Rollbar » Wed Jan 25, 2017 10:15 am

jacquesmm wrote:
Wed Jan 25, 2017 9:55 am
We have exactly that same engine on my son's GF16 and it feels under propped.
We are still in the break in period, no figures and anyway, I don't care about 1 or 2 extra miles at top speed but if I buy a spare prop, it will have a little more pitch.
B-4 you buy a extra prop, try some extra cup on the prop.

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