New D Class Engine

[14-H]

Please check out the SORC Agenda for the proposal on the new three-cylinder D Stock Motor. I'd be interested in your thoughts posted here.

[14-H]

Engine & Lower Unit Specifications

Bass Machines Tohatsu M50D2 Engine Specifications

Three cylinder, two cycle
Manufacturers Rated HP: 50 HP at 5,500 RPM
Displacement: 42.5 cu. in. (697cc)
Bore & Stroke: 2.68 X 2.52 in. (68 x 64 mm)
Approximate Weight: 150 lbs
Lubrication System: Fuel Mix
Induction: Loop Charged
Ignition System: Capacitor Discharge, one coil per cylinder
Dual Swirl Combustion Chamber Heads
Manual Start With Recoil
Thermostatically Controlled Cooling System
Water Pump: In Tower housing above Lower Unit
Enclosed Tower Housing Exhaust
Lower Unit Prop Shaft Diameter: 11/16th in.

General Power Head Description

The Tohatsu M50D2 is a lightweight outboard engine with most parts readily available from Tohatsu/Nissan dealers. The M50D2 is a carbureted model that must be imported under an EPA special competition exemption.

The engine is easily disassembled for repair and inspection. The M50D2 RPM will peak at 7,000 to 7,200. Alterations to prepare the engine for racing include disconnection of the RPM limiter, removal of the tiller handle and installation of a throttle connection, and the crankshaft pins will be spot welded by Bass Machines.

General Tower and Lower Unit Description

The tower is a durable heat treated aluminum casting with an integral water pump and enclosed exhaust housing. The lower unit is manufactured from a high strength heat treated aluminum casting with a smooth brush aluminum finish.

Lower unit gear gears are manufactured from alloy steel, are carbonized, hardened, and spline mounted to high strength shafts.

Assembly and disassembly of this lower unit requires no special tools or jigs. The shafts, bearings and gears are all assembled onto a bearing block that is inserted into the housing and held in place by a locking bar and bolt. The unit is o-ring sealed against water intrusion.


Tower Housing and Lower Unit for Stock Tahotsu M50D2

Dimensions +- 0.25
H D (each side)
8.5 .75

Note: Cast exhaust snout, no dimension, must retain as cast surface.

Minimum Finish Dimensions (inches)
Q T U V
11.7 5.0 3.0 4.0


Minimum Finish Dimensions (inches)
W S R
4.4 1.95 1.95

[crankbearing]

Ed,

Can you post the Agenda on this site for us to read or a link to where we can find it please.

What Powerhead?
What Size?
Manufacturer?
ETC...

Regards,

[crankbearing]

Sorry Ed!

We posted at the same time and you beat me to the punch. By Bass Machines do you mean Sid Bass?

Interested to see pictures.

Regards,

[crankbearing]

Is there a prototype and has it been dyno'd. Tested under extreme conditions for any length of time yet.

What is the projected cost and sources for parts other than Bass Machines?

Regards,

[Eric Engler]

I have a feeling this motor will kill the Merc.

Has anyone run one?

[modifiedoutboard]

Engine dimensions of the Tohatsu pretty much the same as the Yamah 42.6, they are both copies with a few minor differences.
Carbs are small and same size as the Yamaha, I think 1.060" dia , Keep in mind that these little triples have VERY LOW EXHAUST PORT TIMING and a truly STOCK Tohatsu and Yamaha do not have alot of over rev. These engines were designed in a diffrent era to get good fuel economy! I am not saying they are bad, just designed for torque. i think the mercs may have an advantage in the over rev dept.

The Toahatsu and Yamaha bottom ends are bullet proof and will take alot of abuse.

[CSR4C]

The D Stock class is broken and needs to be fixed! It is the only class where there is a Mod equivalent of that there is more mods than stocks. The making of 44SX towers and other parts is just a band-aid for the problem.

I like Sid Bass’s engine proposal. The tower was on display at the Seattle APBA meeting. He has been making gear cases for some time and has a nice product. The question is, will it sell?

Here is a proposal I have that is “out of the box”. It is more or less what the Cal-Ore River Racers are doing. They have more boats at their major races than we have at our nationals in D Stock or D Mod.

1. Power head – Mercury 44 (40 years of production, very large supply of used motors) Stock with 1” KA type carburetors. Possibly allow some aftermarket parts such pistons. Any flywheel, with a minimum weight.
2. Use a spec. external bolt on exhaust tuner that brings the noise level below 90 db (about the same as a 45 engine). Lee Tietze and others could bid on it.
3. Any make tower. V dimension maximum, same as 55H; minimum, same as 44XS.
4. Foot, any make – Specify minimum R dimension and gear ratio range.

With this motor, there would be ample easy to find parts to built it. Price would range from low for a “junk yard special” to moderate for a well built power head and all new lower unit parts. Suppliers such as Sid Bass would have customers for their racing products.

Darrell

[fitsracing]

Starting to sound like a MOD in the stock category.

[CSH12M]

Someday I think Mod and Stock will truly combine and maybe D Stock will die as we know it and be replace by D mod. I am "kind of" against altering classes to make them like other categories. I don't care for CSH and OSY400 and ASH and FAH. Lets let nature take it's course and finally get around to combining all "kneel down" outboard racing catagories.

That said if Bass has a "Stock" motor he would like to get approved I would be all for making it probationary in the D class.
My next question to him would be....can he make a similar motor for the B class using the 20hp 2 cycle Tohatsau of America powerhead? No their is a class that has some market potential. Maybe is he produced both "stock" motors his business could make more profit.

Just a quick two cents worth,

Dean
12M

[brian]

Look at the costs...

This moter will have to be around $5500-$6500 for Bass to turn a profit. The foot and tower are what 1800, now. It is like a 6.5k fishing motor.

I like The Bass product but I think I like being able to build my own powerhead from factory parts. Would we still be able to do this?

Brian

[crankbearing]

Sam and Brian. We did get the 44's approved from Parts and this certainly puts a stain in my shorts with the amount of $ invested to date.

The other point to be made is if you go to the Tohatsu web-site that motor is not even listed as current. So how long before we are in the same situation as we are now for parts availability.

D is an expensive class to get into no matter how you slice it. Everyone says there are no parts but when people work to try and make parts nobody wants to buy them. SO what do the "D" racers want.

I have had this driveshaft thing on hold for over 4 months and so far we have 10 shafts committed to. Why bother!!!!

Jerry Palmquist has 12 - 44xs gearcases empty Brand New, for everyone who wants a gear case - Nobody wants to buy any.

16:21 gears Jerry has 20 - 30 sets. Nobody will buy them. Phil Mcdaniel had 30 + sets of gears in stock for over two years for "D" until he lowered the price and dumped the inventory nobody would buy, now! That there all gone the complaints are well there are no gears available.

So what is the bottom line. I think absolutely nothing will ever change and we will always be in this limp mode becuase everybody wants but nobody will do.

Regards,

[pro350hydro]

Originally posted by crankbearing
The other point to be made is if you go to the Tohatsu web-site that motor is not even listed as current. So how long before we are in the same situation as we are now for parts availability.


Crank

I'm pretty sure this motor is in production as a fishing motor, as I have seen these at my local dealer. It's a nice looking motor.

Unless the part number is slightly different or something

Mike

[14-H]

Originally posted by crankbearing

The other point to be made is if you go to the Tohatsu web-site that motor is not even listed as current. So how long before we are in the same situation as we are now for parts availability.

Regards,

This powerhead will soon not be sold in the U.S. for service engines since it will not meet EPA emissions guidelines (that's why you won't find it on Tohatsu's website for U.S. sales). However, my understanding is that Mr. Bass is seeking an EPA exemption for this motor so as to allow his company to import this powerhead solely for racing purposes. Tohatsu will continue to produce this powerhead overseas for service use for sale in places other than in the U.S.. There is little risk this powerhead will become obsolete. Moreover, it should be possible to continue to purchase parts for this powerhead from dealers into the future.

Interesting point: Mercury is not be able to do this under U.S. law if the manufacture of the powerhead took place in the U.S. even if the engine were sold exclusively overseas. And we wonder why U.S. manufacturing jobs are leaving the country....

[brian]

Just wanted to put this up top.

[121TUB]

i looked in to this briefly and found out that this engine is not avail as a retail engine in us or canada (where i am) But it is still a production engine in the country of origin which means that parts would be available but at what cost. parts would more than likely be pricey but what racing is not expensive its a hazard of pushing engines that far. however parts will be available from cross overs like the 40 horse engine or such but dealers might be a challange(at least where i am from) i think the yamaha route should be considered there are plenty around. the only problem i see by introducing a new engine is that you might end up with a situation like what is happening with the A Merc and the A Omc. i think that you will end up with ond dominating the class which ends up causing racers on a budget to drop out or getting pissed off cuz they cant keep up. saying this the people that did the research might have looked at the power of the tohatsu and found that is the nearest match so that the people that have the 44's can still be competitive

[crankbearing]

What I See is a creation of the exact same problem we are in now. They are allowing a prototype motor in that does not have easily accessible parts. Price will be high as the discussion has determined.

I would have a positive opinion if the motor was from a manufacturer and available parts were around. The fact that the 44 mid is available and could be utilixed to develop a new motor makes all the sense in the world.

The 30 or 40 Merc, 30 Yamaha, etc.. The Yamaha 30 short block is 1500 CDN replacment "New" and is legal currently.

We will have to see what comes of it all.

Regards,

[17W]

OK- It is probationary, why is it not being adapted to the "APBA" Midsection. Our organization outsourced & now has a new midsection (D/25) it needs to be used! At this time, is a new "D" engine needed? (No) (my opinion)

I do appreciate Mr. Bass's efforts & willingness to look for alternative engines.

We need a "B" engine, if service parts for the Hot-Rods are obsolete or just not being manufactured. Time Will Only Tell....

17W :rolleyes:

[17W]

Approximate Weight: 150 lbs, current "D" boats are not going to be compatible for this engine. i.e. weight & displacement.
:rolleyes:

17W