K2FS18

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K2FS18
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Location: CenTex

Re: K2FS18

Post by K2FS18 » Tue Aug 22, 2017 1:21 pm

Prop Numbers.

Powertech 10" SRA4 9 pitch (4 blade SS) ---- Original was a aluminum 9.75" 11.25 pitch 3 blade

With the jack plate in the lowest settings and the manual trim in 2nd setting, the SS prop was doing 2250 rpm's and 22.9 mph.

With JP raised 3" and trim in 2nd setting, the SS was doing 2950 rpm's and 25.5 mph.

Any more height in JP the rpm's would go over 6000. But, she does run at full 6" height, just ease back on throttle.

***********

I lowered the manual trim to the lowest setting (1st setting) and re-ran.

With JP at its lowest --- apparently didn't write those numbers down.

I ran WOT and raised JP until i hit 2950 rpms. JP was at 4.5" up and speed was 25 mph.

With JP all the way to 6", prop ran good, just need to back off throttle so not to go over 6000.

**********

Not sure if this is the right pitch or not.

If I can figure how to post photos from the gallery I will post the JP setup. The JP is installed just about as high as possible on the transom. When in the lowest position, the cav plate is 1/2" below bottom of boat when the manual trim is in the 2nd position and cav plate is parallel to boat bottom and 1" below when it is in the lowest (1st) position and out of parallel with boat bottom. This is even with the motor mounted 1" higher on the JP (spacer was added). It seems I could raise the motor/JP another 2" or so if i could figure out how w/o compromising the JP or transom.



K2FS18
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Re: K2FS18

Post by K2FS18 » Tue Aug 22, 2017 1:43 pm

Image
The top of the 1"x1" aluminum tube is the bottom of the boat. The cav plate is 1" lower than boat bottom and is tilted down when it is in its lowest manual trim position.

Image
The cav plate is 5" above the boat bottom when JP is raised full height. Centerline of prop at nut is 1.5" below boat bottom.


Image
When motor is moved to the 2nd manual trim position, the cav plate is parallel with the boat bottom and 1/2" lower than bottom.

Image
When JP is raised full height at this trim position, cav plate is 5.5" above boat bottom and prop nut is 3/8" below boat bottom.


I was a little light in my weight when I tested as I did not have the second person.

TomW1
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Re: K2FS18

Post by TomW1 » Tue Aug 22, 2017 2:25 pm

K2 before I suggest what you might change your prop to, how far did you have to back off to maintain 6000rpm's. Like I said in my last post the calculations were between a 9 and 10 pitch, but let's make sure you don't need an 11 pitch. The next time you go out, go ahead and let it go past 6000 rpms and see if it will hit the rev limiter. This will not hurt the motor as Yamaha puts it in well before any damage can occur, its like the red line on a car.

Tom
Restored Mirror Dinghy, Bought OD18 built by CL, Westlawn School of Yacht Design courses.

K2FS18
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Location: CenTex

Re: K2FS18

Post by K2FS18 » Mon Oct 16, 2017 10:06 pm

Been able to run the FS18 around the flats lately. This boat does more than I expected. It is super quiet, goes shallower than I need to go, handles the chop pretty good and is much bigger and more roomy than I though it would be. Very happy with how she preforms.

Image

Getting some youngsters on their first Reds on the fly.

Image

Eric1
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Re: K2FS18

Post by Eric1 » Tue Oct 17, 2017 5:49 am

Good report! Thanks! :D

TomW1
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Re: K2FS18

Post by TomW1 » Tue Oct 17, 2017 1:38 pm

Nice report and you have bloodied her also. Well done.

Tom
Restored Mirror Dinghy, Bought OD18 built by CL, Westlawn School of Yacht Design courses.

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