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Tohatsu propeller question 01 May 2021 23:50 #111350

I love that whole rig. It's sleek and lineal. Nice job.
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Tohatsu propeller question 01 May 2021 11:13 #111329

On my 30 horse,  9.9x14.  I hit 35 mph with it, but  I rarely if ever drive at WOT.  I like to cruise.  Need to get a tach..

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Tohatsu propeller question 01 May 2021 02:36 #111327

Yes, that's what I had assumed.  But I've read that my computer-controlled EFI 4-stroke Zuke enforces the rev limit by cutting spark to one of the three cylinders, as you say causing it to misfire.  So I chose a prop that doesn't quite let me reach the rev limit.

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Tohatsu propeller question 01 May 2021 02:02 #111325

There are all kinds of rev limiters, some are “soft” limiters that will just hold a set rpm, usually by retarding the timing and some are “hard” limiters that start to drop cylinders or lower voltage that creates a misfire. The computer controlled fuel injected motors can do whatever the manufacturer wants them to do, it looks like they would use a soft limit and just hold the rpms where they want without miss firing.
Proud Owner of 1956 Vagabond, 1950 Flyer, 1956 Rocket, Co-owner 1952 Flash, 10-1/2 less than VinTin
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Tohatsu propeller question 01 May 2021 01:40 #111323

I'll throw out that my Suzuki 25 HP motor came with an aluminum Suzuki 10 1/4 x 11 prop.  (The 30 HP Zuke comes with a 10 1/4 x 12 prop.)  I ran my prop for a few weeks and collected some numbers, then bought a stainless 12-pitch prop.  I didn't get the change I expected from the 12-pitch prop, so I took it and my original Suzuki prop to a local prop guy to ask him about cupping the stainless prop.  He started by measuring both props with a simple protractor-type thing.  The Suzuki prop, which is clearly marked as 11-inch pitch, measured as a 12-pitch prop!  The stainless one I bought also measures as 12-pitch (as marked).  Lesson I learned as that it is probably prudent to have a prop measured, rather than assuming it is what it says it is!

BTW, this local guy said he wouldn't cup the small stainless prop for me.  Said he'd be happy to do the aluminum one, but not stainless.  He told me he has to beat the he77 out of stainless to cup it, and he wasn't sure the splined tooling shaft he puts the prop on would survive the beating.  He said he broke a shaft once making adjustments to a small stainless prop.  And the shaft costs more than he could reasonably charge me for cupping the prop.  He said he does bigger props all the time.  But didn't want to do my small one.

I'm curious - how does the Tohatsu behave when you hit the rev limit?  My Zuke starts running rough like poo when you hit the limit, like it's punishing you.  I had assumed it simply wouldn't go any faster and I could just ride it at the limit.  But it starts running real rough - not where you want to be.
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Tohatsu propeller question 30 Apr 2021 23:32 #111321

Hey Ray,
The very little data I was able to get showed around a 0.5 mph drop. I didn't get a chance to really test whether the cupping changed other performance characteristics. I would like to put the Turning Point prop back on and redo some testing before reducing the cupping.

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Tohatsu propeller question 30 Apr 2021 16:09 #111319

Hey Nick,
Did you get a speed change along with the 700 RPM drop?
Proud Owner of 1956 Vagabond, 1950 Flyer, 1956 Rocket, Co-owner 1952 Flash, 10-1/2 less than VinTin

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Tohatsu propeller question 30 Apr 2021 14:51 #111318

Hey Don,
My 30hp Tohatsu on my Vagabond came with a 9.9 x 13 prop. The motor max rpm is 6250 and I have had the alarm sound and the tach showed 6250/6280 on a few occasions when it is windy and choppy. This is a WOT. This is the prop I continue to use.

My friend has the same motor on a Rocket II and it came with a 9.9 x 14 prop which I borrowed and ran. At WOT the rpm seemed to have dropped about 250 rpm and may have increased speed 1 mph. It is difficult to say much about mph with changes in wind, water chop, and river flow.

My friend purchased a Solas 9.9 x 13 to have a spare prop. It looked exactly like my Tohatsu prop and when I ran it it had the exact same results as my Tohatsu 9.9 x 13.

I purchased a Turning Point 10 3/8 x 13 prop to have a spare and it was setting off the alarm and the motor shut down one cylinder. I had the prop cupped a little and the WOT rpm dropped a surprising 700 rpm. I plan to have it un-cupped some someday. Meanwhile it is a spare prop.

forwhatitisworth,
Nick

 
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Tohatsu propeller question 28 Apr 2021 21:29 #111293

Hopefully Nick will chime in, he has experimented with props on his 30 Tohatsu.
Proud Owner of 1956 Vagabond, 1950 Flyer, 1956 Rocket, Co-owner 1952 Flash, 10-1/2 less than VinTin

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Tohatsu propeller question 28 Apr 2021 13:58 #111281

My Tohatsu 30hp came with a 9.9 x 12. It will over rev at full throttle.  Need to increase pitch at some point.Scoot
56/7 Vagabond 1, 57Clipper

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