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.

[Ron Hill]

https://www.ebay.com/str/ronhillsignaturepropellers/Mercury-V6/_i.html?store_cat=3155846012

https://www.facebook.com/winracepropellers/

We are casting these for Ollie. I don't know if he wants to sell castings.

Ollie and I have been friends for many year, he's a damn good propeller maker.

[dandrews75]

LMAO! APBA has A Plan? You doing standup now Ron? They have a plan alright………..The people putting rigs together right now have done more than those guys have done the last 2 years with the engines that were given to them! People putting outfits together are buying their engines! Buying a Morse steering kit, go figure………..you said that right off the hop lol. This is so far ahead of where racing is currently at, you can buy engines, parts, props from anyone. Your motor has resale value everywhere because when done with it someone will buy it to put on their fishing boat. With these props your making here, everyone is getting the same thing. With the current situation with stock outboard props it’s a crapshoot at best.

[Ron Hill]

When I was three, my dad blew his C Service motor all to hell. For at least two years, my dad would have me re tell the story to any of his friends that had not heard that he'd "Blown his C Service all to hell."

I enjoyed the attention, and teaching for 38 years allowed me to tell jokes, that many of my students liked.

When APBA had Conventions and people got to speak, I usually got more laughs than anyone. Frequently people asked to speak before me, and they didn't want to follow my "ACT".

The sad part of APBA, it the "Powers that Be" have positioned themselves to be in control. There was a time, if a Maverick, like Bob Nordskog wanted to be President of APBA, he ran for the office.

NASCAR talks "Business Model" all the time. They plan for growth and they are getting it. But, NASCAR sponsors races, they don't sit in their Ivory Tower tell racers to send them money...

A B Runabout class, being brand new, could shake up the racing day. Maybe run, 30 lap heats. Or run two 15 lap qualifier's. Run some 660 Foot Drags...The reason people have a trailer full of boats they want to be on the water more.

Run B Runabout 15 minutes, plus one lap....

Start a "Youth" Division and an "Adult" Division. Same boat, different weights.

Run time trials, start off docs slowest first....or fastest first.

As far as stand up goes, get me a beer or two and a crowd of boat racers and I'll have them laughing all night...

I could talk about the time, Marcel Belleville rode with me in F Runabout, and when I'd scoot back, Marcel's butt would hit the spark plugs and he'd jump on top of me...Monsieur you are sparking me he'd yell over the top of my Konig. (He spoke French but only when excited).

[GoFast Cracker Bay]

The Tohatsu and Mercury 20's are remarkably similar. I wonder if Tohatsu is making them for Mercury or if they started with the same deisgn and made it theirs.

[Mini Max]

The Tohatsu and Mercury 20's are remarkably similar. I wonder if Tohatsu is making them for Mercury or if they started with the same deisgn and made it theirs.

All Mercury badge engines 30 hp and under are manufactured by Tohatsu.

[Ron Hill]

Made some 15, 16 and 17. Reported speeds were 44 with the 17.

[Mini Max]

Made some 15, 16 and 17. Reported speeds were 44 with the 17.

True, but it was a one time, first try with a 480 lb motor, boat and driver. (I am 200) No Tach fitted.

The Carolina Virginia Racing Association has purchased a 4 stroke Tohatsu and commissioned John Runne to build a purpose built runabout. It will be raced and used in their driver school. John has all of the Hill Marine props and will give them a fair test. We think 50 mph is a reasonable expectation.

[Mini Max]

The four stroke engine is legal to race 15SSR and BSR APBA Stock Outboard. 2023 there were 30 drivers scoring points in 15SSR and 0 drivers scoring points in BSR, although 63 drivers scored points in BSH. I assume the wisdom is that the 20 four stroke can race with 15SSR provisionally but when numbers justify then BSR would race as a four stroke 20 class.

[dandrews75]

What rpm were you running and prop diameter? In my opinion we need to build new boats to match the engine. For a utility I’d look closely at the GT15, 30 and Dillon boats for design baseline. For a hydro you need a longer, wider, deeper boat with rear shoes to decrease hull drag. Would also go to a boat mounted water pickup to allow the motor to be jacked up as high as you want. I’m thinking bigger diameter props and keep adding pitch til you hit the rev limiter. Use an adjustable jack plate or transom to make height changes quickly to figure this out quickly. We ran 40+ with 20 Merc’s on tiny titans and flat bottom river racers back in the 70’s and 80’s as kids. The speed is there, just have to unlock it. This is an EFI engine which is totally opposite of a carbed engine in that the carbed motor you can under prop it and spin the hell out of the wheel to get speed out of it. As a point of reference I had a 16 ft crestliner utility with an Evinrude 50 Etec on the back. I quickly found out I could not under prop it, hit the rev limiter right away. I kept putting more pitch to it til it ran out of steam and that was 21p and 46.4 mph. Respectable but given the power to weight ratio should have been able to run 52-55 which I believe could have been achieved with a low water pickup nose cone. So in summary here’s what I would concentrate on; prop match to EFI and new hull with the least amount of drag possible. For a hydro I would use a bigger version of the HARM J boat (same boat that HRL novice drivers built last winter, Karelsen/Kelsen design similar to the 70’s early 80’s boat Ron posted on BRF FB). Wider cockpit, the extended nose on the boat would accommodate hotfoot for sit down ride. Make the seat movable for/aft to help find the balance of the boat. So 10’8”, 40” wide air trap, 2.5 degrees AOA, etc. I see that a group headed by Dewald has decided to adapt a racing foot to the 20 4 stroke. I would say the ROI is not good considering the gains that could be made with a low water pickup nose cone or remote water pickup for a lot less money. Speeds were 51 on the utility and 48 on a hydro. I am certainly not a proponent for a specialized foot and perpetuating the current status quo which does nothing but hinder growth and opportunities in boat racing.

[Mini Max]

Engine height I set with the same APBA Brown height checker I use on my CSR Yamato. CL of prop shaft 3/4" below the bottom. Up to 85 mph the round nose mercury gear case on the 300 hp Mercury's I use on some cats I build is better than the pointy nose low water pickup "Sportmaster" There isn't going to be any gain from spending a lot more money to modify the 4 stroke with parts no longer made.

Yes you might want to use the left hand rotation gear case because of all the props on dusty shelves but the European prop makers LAK and Winrace provided me thru hub exhaust props from the GT-15 classes and Ron Hill sent me over the hub exhaust RH props he made.

The numbers I heard with the 20 four stroke modified with a "A" racing lower unit were the runabout 44 mph and hydro 51 mph. 44 was the speed the first time I tried the box stock Tohatsu with either the European props or the ones Ron made. I come at this as an average guy, not from a racing family. It took me a year to find a good C Yamato 102 and a refurbished D Tohatsu 50. To get the 20 took 15 minutes, the time it took to drive to the marina and take my pick of the ten 20 hp Tohatsu's in stock.

[Mini Max]

The c/l of the prop shaft 3/4" below the bottom is the same as the UIM GT-15 and GT-30 classes and the APBA stock runabout classes. The Tohatsu has a electronic guardian mode for overheating and no need for modifying the engine for low water pickup has become evident. There are many "tricks" we use to get water to a stock engine that are non invasive but why? The engine cools without messing with it so far.

By buddy Harry Schoell is also building me a prototype prop. He is 80 and we are working to get him to the Top of Michigan Marathon 2024. Before Todd Anderson provided me my first props from LAK, Harry designed a prop for the four stroke 20 that he is building in his garage. Props and boats. Boats and props. My DSR came from a sketch he made of his CSR he built in the 60's.

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[dandrews75]

Ok, so no cooling issues so nothing to do there. If you are going to run that boat you need to add a pad to the bottom. I would say 1” thick by 8” wide and 2’ long blended into the boat. It might not handle well with this. Other option is to add steps. You have to much drag at this point. Really need a Dillon boat or a smaller version of a delta, critch or voodo. In fact, I saw an 11’ delta on kijiji in the summer, they are really uncommon. A Zorkan might work also. I think this is a boat issue at this point, need something to handle the high c of g and be able to set the balance. My dad had a 1973 14’ Springbok with a 1985 Mariner 25 hp that would do 42 mph with just me in it. That whole outfit weighed 292 lbs. The GT 30 kilo record is almost 60. So there is a lot on the table with these 4 stroke engines. Might want to check with the TBoat guys on the High Performance Boating Canada website.

[Mini Max]

APBA stock outboard has a very few boat rules but one is no more than a 5/8" longitudinal step in the hull bottom and no transverse step. Tim Kurcz bought me the Dillon plans and these photos are of his Ropp/Kurcz design DSR "Summer Daze" a high point champion. His pad has the outside edges beveled. This makes the boat track better and gets the thickness to within the rules.

My friends had a rule when bar crawling which was "go ugly early" then the pressure was off to find someone better to take home that night. I never bar crawled but I have had a lot of boats and I suppose "go ugly early" got me boat riding first, and now the pressure is off to find something better.

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[dandrews75]

You were reading my mind, I was coming back to comment about Tim’s boat. I think an 11-12 foot version of this boat would be the ticket. I also believe we may need to get away from the current rules governing utility boats. I can see class realignment including or resembling GT15/30, T750 and T850. The TBoat classes are raced in Ontario and I really think they should be included in stock outboard. Will be interesting to see what HRL has up their sleeve. They attempted a takeover of CBF at the November AGM. Wondering if an outboard series is in our future. NBRA has made the engine legal for hydro classes. So change is coming. I think we are pretty well at the wall with the current boats being tried. Like anything once more people get involved advances will come quickly. Too bad Ed Karelsen wasn’t here still, I’m sure he would’ve sketched something up.

[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.

[Mini Max]

Daniel Pearson is a Suzuki Dealer and gave a 20 hp engine to one of the racers. Unfortunately they were too busy to put another boat together. The Suzuki prop shaft is a 10 spline, different than the 14 spline Tohatsu. I did have a Suzuki GT-15 prop from Winrace in Norway on standby this year but they elected not to purchase it. Ron Hills props have a pressed in hub fit for Tohatsu but easy to fit a Suzuki or Yamaha hub.