I am not familiar with the outboard in question. Is there a 20 horsepower version that uses the same powerhead and lower unit for which remote controls are available? If so, I would think that the remote controls ought not know the difference between being connected to the 20 horsepower or the 15 horsepower version. That would be the first thing I would check in to.
There might some stateside product development engineers who work for Yamaha who might be able to answer that question. They used to do some product development stuff out of their facilities in Cypress, California. I don't know if they still do or not, or how to get in touch with the right people if they do.
But while I am thinking out loud.......
Is there a reason why the remote controls used is APBA race boats in some outboard-powered hydro and runabout classes couldn't be made to work?
What I am talking about here is a "cable and sheave" steering system and a simple, generic push / pull dual-lever control wherein one lever does throttle duty and the other does F-N-R shifting.
The steering system referenced above is what all remote controlled outboard boats used to use. My old 13' Boston Whaler that I used to have had this kind of system and it worked very well. That old Whaler had a darn sight more than 15 ponies hanging off her tail, too. It didn't have steeing kickback and the vessel didn't fishtail or do any of the negative things that boats with this kind of steering are sometimes said to do.
Basically, for those who've never seen it, it works like the steering on a soapbox derby car. You've got a steering wheel mounted on a shaft, and a drum is also mounted to that same shaft. Cable is wound around the drum, with the tag ends leading back to the outboard. Sheaves (pullies) are used where the cable has to make a 90 degree bend. They're also attached to a bracket affixed to the front of the outboard with one on either side. The cable ends go around those and terminate at smallish springs of 50 to 80 lbs rating on either side of the outboard. You turn the wheel to the right, the cable pulls the outboard to the right, causing the boat to go to the right. Same deal when you turn to the left. And the springs keep the cables taught if the motor is tilted.
I plan on re-powering my "can" with a 50's or 60's 18 horse Johnson / Evinrude and using the cable and sheave method for remote steering. The parts to make this work are still available from companies that cater to racing crowd.
Those same companies sell a throttle / shift control that is pretty much the same thing as my old Whaler had mechanically. You've got two handles -one for throttle and one for shift, with sector gears on the ends. These mesh with a rack-type flat gear affixed to the cable ends. The result is push / pull control. All that remains is fabbing up a little bracketry for cable stops, and you've got remote control.
This is pretty dang easy with 50's and 60's OMC outboards, which is why I'm looking to replace my 1960 vintage 10 horse Johnson with an 18 horse from the same period.
That said, I don't see why the race boat stuff couldn't be adapted to just about any small outboard.
Whether it is legal to do so or not I can't say. On an older hull like mine, made when cable and sheave stuff was still available through marine dealers catering to the pleasure boat crowd, I suspect it probably is legal. On a newer hull made when single push-pull steering was common, I suspect it would not be.
Don't know why it shouldn't be legal. Outboard hydros go a heck of a lot faster than my junk ever will and they use this stuff.
T-C
