Yamaha Outboard

[greenapple]

I was wondering if someone could answer my question. I have an Yamaha 75 4 Stroke DOHC,L4 on my 17'Triumph that I am very happy with. Looking at the specification on the 75hp and the 90hp, the bore x stroke are the same. Also the size (displacement) and weight is the same. The question is "are they the same motors"? And if they aren't, what makes them different in Horse Power?

Thanks,
Greenapple

[Putershark]

That little in horsepower difference is more than likely in ECU programming for the injection unit, and maybe camshaft profile. I bet if you were to call a dealer that you would find those 2 part numbers different for each engine.

[Tygh]

Go to Iboats.com and they have a Yamaha motor forum. Lots of resident experts there that can answer your question.

[greenapple]

Putershark and Tygh,
Thanks for the info. Putershark I believe that could be the answer on the extra HP. Tygh, I went to the site you gave me and if I was selling a boat that would be the place to go but I couldn't find any forums for Yamaha outboards. Thank you anyway~~~Greenapple

[Tygh]

Here is the link to their forums:

http://www.iboats.com/cgi-bin/ubb/ultimatebb.cgi

A wealth of information on motors on their site.

[greenapple]

Tygh,
Thank you for the site, went there and it is a wealth of info on everything. Great site!!!! Thank again.
Greenapple

[suitekids]

The only difference according to the part numbers is the ECU, The cam profiles are the same, Obviously the timing event on the cams and a richer fuel/air charge programmed in the ECU make the extra 15 HP. And in retro that is a significant HP increase on a small HP motor, This ECU is available and is very cheap for the gains (428.00) It is part #6D8-8591A-00-00. On your 17cc with a 13.25x19 Yami Proseries prop, 46mph is about top speed trimmed out with GPS, and hole shots under 3 seconds.Oh yeah I forgot to mention,you need to pull the restrictor out of the breather assembly. Hope this helps