20 HP Mercury and 20 HP Tohatsu Racing Propeller

[Ron Hill]

With encouragement from Bill Gohr and a few other from APBA, I', making a racing prop for the 20 hP Four Stroke.

The colored props are 3 D Print made by Winrace Propellers in Norway.
3D Printing is the future of racing propellers.

[dandrews75]

I was wondering when this was going to happen. Friend of mine who was making props had suggested it to me 15 years ago. Nylon props are nothing new. We have one from Mercury, 2 blade blue in colour for the 22 ci 20hp Mercury circa 1978 there abouts. I had recently did the torque calculation for a 20 HP motor and it is just over 10 lbs and as the rpm goes up the torque output goes down. So these small engines put out very little torque so you don’t need to get into an exotic overly complicated material.

[Albert]

This is just too cool. Imagine being able to print your own prop from nylon resin at home? I wonder what the longevity is going to be like?
Ron will you be printing these yourself or having someone local to you do it?
Did you receive your motor yet? Wish you were closer I’d love to help test this set up and learn about it first hand.

[Ron Hill]

Propellers are usually made in wax, then cast in Stainless Steel. This is called the lost wax process.

3D printing a prop in plastic, plastic will replace the wax.

The propeller will still be cast in Stainless Steel and be finished by hand of a CNC mill.

[Albert]

Any progress on the prop project?

[Ron Hill]

One problem I'm having is people keep buying props, so it is hard for me to make props and to give away.

I was told the APBA was given 2-20 HP 4 Strokes to test.

I offered Chris Fairchild, to send one to me. I'd pay the freight.

I said, Ernie Dawe builds boats and lives 120 miles away and 70 miles from a perfect test lake. Send me the motor, I'll get with Ernie and build a boat, and have Ernie's granddaughter, who races test it.

I was told he loaned the motors to Hearn and Pavlick.. Pavlick has had his since last year.

I thought well, you know, if they have their plan, why do they need me?

So, I'm making 12- 10 1/2 X 15 Semi Cleavers and 12-10 1/2 X 16 cleavers. But I think I'll put them on E-bay and sell them. APBA has A PLAN.

OH, 3D printed props are casting like POPCORN....Here is a picture of the first casting pictures soon! Came out great!

[Albert]

That looks great,
Some of us may even be willing to buy them as is and finish them ourselves.
I have been keeping an eye out for a used Tohatsu 20 4t but they are thin on the ground around here. Can't quite justify new this year but maybe next.

[dandrews75]

Take a look at the Winrace hulls online, very similar to Tim’s boat also. They are uncommon over here also but from what I gather they are using a 13’ boat in GT15&30. This would mean that a Delta, Critchfield, Voodo, Allison, Checkmate, etc would work. I also read surface riding props are the way to go with these boats, 10 mph difference.

[Mini Max]

Any boat with a 20 hp four stroke can race APBA in BSR or SSR15 in 2024 and 2025. Any boat, any weight, any prop shaft height.
Therefore any GT-15 GT-30 with a 20 can race in APBA. I am in fact looking at getting a 30 Hp Tohatsu to fit to a boat. Todd Anderson has supplied a LAK prop for it that came last week. I have had a new Yamato 331 on order for 2 1/2 years, so maybe they let me run that 30 hp as an exhibition in CSR? 100% I will make sure the boat will fit the GT-30 rules. How cool to go to Europe and race there?

[dandrews75]

So any boat and any 4 stroke 20 hp. So Mercury, Tohatsu, Suzuki, Honda and Yamaha. For me the Yamaha is a non starter at 126 lbs. all the others are between 94 and 104. I wouldn’t over look the used market for these engines either. I saw a Merc for sale for 2000 CDN that had 10 hrs on it earlier in the year. Saw a brand new Suzuki for 2770 US today. The Honda is interesting in that it is the largest displacement 20 and is carbed and has a long production run, been the same motor for eons. If I were you I’d put the 331 in the review mirror. There is going to come a time in the not to distant future where the exporting of this engine is going to stop. The race sites in Japan own these engines not Yamato and they answer to the race sites. They only build what they request. There is only one person handling the export shipments and that person is not very enthusiastic about the extra work. It wasn’t that long ago that Yamato brought in a consulting firm to review their whole operation to see where they could cut costs. Their whole business model changed and they saved millions of dollars. They are making changes to the motor frequently enough where things like ignition parts are not compatible with an earlier production motor. You’ve been waiting how long for one? The answer of what to do is obvious.