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FROM ANOTHER THREAD:

mattmak wrote:

DoktorC wrote:

the short 50 case doesn't bolt right on, does it?

Has anyone actually bolted one on and double checked lengths, spline mesh, everything, and ran it!?
Would be cool to get other gear ratios available for the 40/50.. but last I checked the 30hp ratio was also 1.85:1?

HERE IS JOHNSON'S WORLD RECORD YAMAHA MOD C
http://www.boatracingfacts.com/forums/a ... 1221568447

Modified, 35 cubic inch, 3 cyl Yamaha 30 (50hp carbs, hand-made tuner, specialized gearcase, motorcycle pistons, etc )

boat + driver + motor = 550 lbs

From UIM
Speed Record #2925
20/03/1988 J. JOHNSON USA Outboard Performance Class / Mod. C / Speed 80 mph
5 Mile Average lap speed record #2993
20/04/1989 J. JOHNSON USA Outboard Performance Class / Mod C / 5 m 69.37 mph
Motor had a nose cone, but no low water pick ups....NOTICE THE SMALL CLAMP BRACKET...original 30 hp part

HERE IS A 30 hp LOWER UNIT ON A 40/50 hp YAMAHA
This one has low water pick ups and running factory 40/50 clamp bracket....so you could add factory power trim
https://www.screamandfly.com/attachment ... 1194693853

IF THE 30 FITS THE 40/50....THE 40/50 FITS THE 30
You can see the difference between the 30 lower unit and the 40'50.
Here is a 40/50
https://images1.showmethead.com/nlarge/ ... 661198.jpg

That’s pretty cool.....
Now, can a small diameter case be made to fit on a 90hp 3 cylinder?

yes!

Don, I don't see the evidence in those pics. I just can't tell which is which.
Also, I just double checked my previous research - the 1987+ 3cyl 30hp (6J8) has 13/24 gears just like the 40/50 3cyl.

It is looking like they do both have the same driveshaft/crank splines.

The scream and fly link is a 30 with a 30hp gearcase but has a 40/50 clamp (which mine is getting over the winter) and the last pic is a 40hp tiller with a 40hp gearcase.

Why do we want to switch up the case on the 30? Prop selection would be reason enough for me but I don't think the limited prop selection for the 30hp would justify it for use on a 50hp. Overhub stuff would be ok I guess but small diameter thru-hub would be almost impossible to find vs. The merc stuff that bolts on the 50.

DOK. I have a short shaft 30 hp yamaha with the single ram 40 trim on it. I also have one of the original Mod C Jimmy Johnson lower units. I wanted to use it on my MOD PRO 50 short shaft because it is smaller, I have a prop for it, and it looks better. The stock 50 short shaft lower unit fits the 30.
As I mentioned on the other thread and you agree.....there is a much better prop selection with the 40/50 lower unit....ideal combo for the 30 is the 40/50 lower unit and the 40/50 factory power trim. It all works. IF? someone happens to have the later 40/50 version [1996 and newer] those models have a different shift system rather than the push-pull shift on the earlier 30-40-50 models

some pics from Don:

SUGGESTIONS:

IF? your looking for a 40/50 or 30 hp yamaha short shaft drive shaft?
Check the dealers used drive shaft stock.....when everything moved to long shaft.....dealers switched the drive shafts in their short shaft parts motors to long shaft or they used the parts from the short shafts to fix long shaft models.....the lower unit parts are the same on both the long and short......new short shaft drive shafts are NLA.

IF? your looking for 30 hp props.
You can get aluminium 9 7/8 X 14 thru hub for Approx. $120.00 on line
One of the best ideas for performance stainless props are Ron Hills changeable hub kits.
You can switch the hub kit to use the prop on different motors.....Kits cost approx. $100.00
The 30 hp yamaha has a smaller diameter housing so thru hub props for the 40'50 hp motors are too large.
Over the hub props can be used with a blow-out ring...same result.
Prices for Ron's props have increased.....the quality has improved as well.....most buyers have found his latest props work well right out of the box. FASTEST 50 HP YAMAHA ON A DELTA HAS A RON HILL PROP OUT OF THE BOX.....58-59 MPH!! ....IMPRESSIVE!!
Look for a used Ron Hill prop that has the hub kit......you only need to get the hub kit for your model motor.
http://www.boatracingfacts.com/forums/a ... 1505695032

E-MAIL
How does a Pro 50 with a non-worked Ron Hill prop get to 59 mph without any setup time?. Either the prop is magic or the motor is strong!!

GOOD QUESTION.....likely BOTH!......plus the boat must be very good......it is a light raceboat single seat, center steer....also that is it's top speed as a lake runner.......we can run 56-57 with our 50 hp Tohatsu on the straight during a race......if I went up from a 11 x 18 to a
11 X 20 we could run the same 58-59 mph......as a lake runner.....so it's doable

ABOUT THE 50 HP TOHATSU
Here our T750 class is dominated by the 60 hp 2 cylinder OMC.
In Europe the class is mostly 50 hp Tohatsu.
In fact the speed record is held by a Tohatsu at 65 mph.
Our OMC's if set up for the speed record would better 65 mph.

SO WHY IS OUR TOHATSU SO SLOW?
I wanted to help the T750 class grow, so we put together the outfit.
GIG found a short shaft Tohatsu on a pontoon boat in Florida for $250.00 american.
There were NO short shaft models in Canada at the time.
I got the Florida motor.....it had a welded block....bent prop shaft....damaged skeg.....terrible paint.
It ran fine......so loose and quiet you could hardly hear it running
Only change...plastic reeds.
We raced it as is.

Hounddog,


Do you have 30hp lower unit for sale ?