View Full Version : Yamato 4 stroke 400 series race motor

07-08-2003, 09:44 AM
Fresh from Japan courtesy of Ric Montoya, North America's Yamato importer.

Before you do a whole lot of speculating this is just a prototype, the delivered motors may look exactly like this or nothing like this.

I see bosses for the valve guides spread far to the side of the head casting, indicating to me that this version at least uses rocker arms on the overhead cam. I also see a row of screw recesses on the lower unit that probably indicate a split lower unit rather than the current rear loader. My guess here is that the new powerhead needed a water pump. I also see a vacuum pot on top of the carb, I guess it couldn't stand to have the the throttle popped wide open at low rpm.

Don't get visions of converting the exhaust to a pair of open headers.......
Mod rules say any new motors may not have loud exhaust

07-08-2003, 11:10 AM
Dang that's a neat lookin' piece. Wonder what that sucker's gonna cost?

wild child2
07-10-2003, 07:54 AM
Sam how about giving a little credit to Brad Walker and HydroRacer.Net for these very rare photos :D

heath brinkley
07-10-2003, 03:14 PM
what kind of horsepower?

07-10-2003, 09:27 PM
Yep, Dan is right, you can find these on the discussion on his board and the images came to it via Mr. Walker.

HP is probably in the 30-35 range, weight is supposed to be within 10 pounds of the current 302 Yama-toe (as the makers pronounce it).

07-20-2003, 05:04 PM
Sold refurbished, not new, the current 300 series 2 strokes were $1400 last year, closer to $1900 now. Other than competition to grab the first ones, they probably won't squeeze racers too much for the 4 strokes.......I'd guess something in the $2000 range.

They get their money out of them when they are new......outboard racing in Japan is like horseracing here.....very much money.....millions and millions of dollars (hundreds of millions of yen) the few hundred thousand dollars the motor's cost to develop and produce is instantly absorbed.

Selling us the motors is kind of like horserace tracks selling used horseshoes or Greyhounds being rescued from dog tracks; on Hydroracer.net I equated it to selling used shear pins........the production cost doesn't really enter into the sale price.

08-03-2003, 02:59 PM
Originally posted by Mark75H

HP is probably in the 30-35 range, weight is supposed to be within 10 pounds of the current 302 Yama-toe (as the makers pronounce it).

Wish they'd get the HP up to ~50 on one of those motors - and keep the weight down close to what the 302 is.

Sam, what's your best guess as to HP of a D/E (44) mod?

08-03-2003, 05:59 PM
My guess would be about 60hp. Consider that they run pretty equal to the OMC 45ss which is in essence a 60hp twin with a racing lower unit.

There is no incentive for Yamato to increase the power on their racing motors. What the Japanese want to bet on is the driver's racing skill and the driver's prop modifying skill, with everything else remaining the same from year to year.