C19 Stretch and re-build - Launched!!

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TomTom
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Re: C19 Stretch and re-build - Launched!!

Post by TomTom »

Hi TomW - my engine is a 2012 F150BET - I believe having looked it up that it’s max rpm is 5500 … so maybe I am closer than we thought?

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TomW1
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Re: C19 Stretch and re-build - Launched!!

Post by TomW1 »

Okay Tom the motor spec I got were for 5000-6000 and peak HP at 5500. But let's go with yours as they have made motors for other parts of the world before, I also just found the same specs today. So, in that case your prop needs no change. If you want to go to a 4blade drop to a 15 pitch if you can find the diameter, it should be on the barrel of the prop. Or if not get me the manufacturer and I can probably find it. They usually use one diameter with multiple pitch sizes. Or, if it is from a local shop you can take it to them and have them give you the diameter and recommend a 4Blade.

Let me know what you want to do on the 4Blade. Tom
Restored Mirror Dinghy, Bought OD18 built by CL, Westlawn School of Yacht Design courses. LT US Navy 1970-1978

TomTom
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Re: C19 Stretch and re-build - Launched!!

Post by TomTom »

TomW1 wrote: Wed Jan 19, 2022 3:23 pm Okay Tom the motor spec I got were for 5000-6000 and peak HP at 5500. But let's go with yours as they have made motors for other parts of the world before, I also just found the same specs today. So, in that case your prop needs no change. If you want to go to a 4blade drop to a 15 pitch if you can find the diameter, it should be on the barrel of the prop. Or if not get me the manufacturer and I can probably find it. They usually use one diameter with multiple pitch sizes. Or, if it is from a local shop you can take it to them and have them give you the diameter and recommend a 4Blade.

Let me know what you want to do on the 4Blade. Tom
Thanks Tom - what do I buy myself with a 4 blade?

Could I get lower RPMs at trolling speeds?

Could I get a faster top speed?

Ive heard certain propellers are better at keeping the nose down on a boat ... is this true?

TomW1
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Re: C19 Stretch and re-build - Launched!!

Post by TomW1 »

TomTom wrote: Thu Jan 20, 2022 11:41 am
TomW1 wrote: Wed Jan 19, 2022 3:23 pm Okay Tom the motor spec I got were for 5000-6000 and peak HP at 5500. But let's go with yours as they have made motors for other parts of the world before, I also just found the same specs today. So, in that case your prop needs no change. If you want to go to a 4blade drop to a 15 pitch if you can find the diameter, it should be on the barrel of the prop. Or if not get me the manufacturer and I can probably find it. They usually use one diameter with multiple pitch sizes. Or, if it is from a local shop you can take it to them and have them give you the diameter and recommend a 4Blade.

Let me know what you want to do on the 4Blade. Tom
Thanks Tom - what do I buy myself with a 4 blade?

Could I get lower RPMs at trolling speeds? A couple hundred.

Could I get a faster top speed? No top speed will decrease slightly.

Ive heard certain propellers are better at keeping the nose down on a boat ... is this true? Yes, read on, it depends on rake and cup.
You will lose 3-4 mph top end but gain an easier handling boat. Also, in rougher water it will help in steering and handling. This means keeping the nose down, but this depends on the rake of the prop. There are 4 parts of a prop diameter, pitch, rake and cup. The diameter and pitch set the basic size of the prop and speed of the boat. Rake and cup indicate how the prop will perform. Increasing rake or cup by too much will increase bow lift. Each increase the water held on the blade.

In conclusion a 4blade prop with low to moderate rake and cup is what you are looking for. In whatever diameter you find by 15 since we decided the 17 pitch was fine. Let me know what brands are available to you and I can help. Solas are available worldwide, I don't know what is available to you.

Let me know if I can help more. Tom
Restored Mirror Dinghy, Bought OD18 built by CL, Westlawn School of Yacht Design courses. LT US Navy 1970-1978

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Re: C19 Stretch and re-build - Launched!!

Post by TomTom »

Hi TomW - many thanks. I will measure the diameter next time I am near the boat.

If my sole intention was to be able to troll at the lowest possible rpms would a 4 blade still be the way to go and do you think I could shave some rpms off my 2000 rpm/ 7kt speed?

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Re: C19 Stretch and re-build - Launched!!

Post by TomW1 »

Tom, I would say yes as the 4blade grabs more water, you should be able to get down to 800-1000 rpms. This should give you 3-5 mph.

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

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Re: C19 Stretch and re-build - Launched!!

Post by TomTom »

TomW1 wrote: Sun Jan 23, 2022 11:54 am Tom, I would say yes as the 4blade grabs more water, you should be able to get down to 800-1000 rpms. This should give you 3-5 mph.

Regards, Tom
I have measured the diameter and it is 13.3/4 inches with 17-N on it….

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Re: C19 Stretch and re-build - Launched!!

Post by TomTom »

TomTom wrote: Tue Jan 25, 2022 1:49 pm
TomW1 wrote: Sun Jan 23, 2022 11:54 am Tom, I would say yes as the 4blade grabs more water, you should be able to get down to 800-1000 rpms. This should give you 3-5 mph.

Regards, Tom
I have measured the diameter and it is 13.3/4 inches with 17-N on it….
Also have some updated speeds … these are off the digital speedometer that works on a pitot tube/ water pressure…

5400 = 40 mph
4500=34 mph
3600 =25mph
3400 =23mph
3300=21mph
2800- 15 mph
2400 = 11-13 mph
2000- 2200 = 10 mph
1800 - 9mph

TomW1
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Re: C19 Stretch and re-build - Launched!!

Post by TomW1 »

TomTom wrote: Tue Jan 25, 2022 3:23 pm
TomTom wrote: Tue Jan 25, 2022 1:49 pm
TomW1 wrote: Sun Jan 23, 2022 11:54 am Tom, I would say yes as the 4blade grabs more water, you should be able to get down to 800-1000 rpms. This should give you 3-5 mph.

Regards, Tom
I have measured the diameter and it is 13.3/4 inches with 17-N on it….
Also have some updated speeds … these are off the digital speedometer that works on a pitot tube/ water pressure…

5400 = 40 mph
4500=34 mph
3600 =25mph
3400 =23mph
3300=21mph
2800- 15 mph
2400 = 11-13 mph
2000- 2200 = 10 mph
1800 - 9mph
Tom was that your top speed at maximum rpm? Did you have any rpm's left? Tom
Restored Mirror Dinghy, Bought OD18 built by CL, Westlawn School of Yacht Design courses. LT US Navy 1970-1978

TomTom
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Re: C19 Stretch and re-build - Launched!!

Post by TomTom »

If I trim up slightly I can pick up about 2 extra mph … I haven’t seen the rpm go above 5400.

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