yamaha 70 ces

[Fede 97]

Attachment 57425

[fast213]

fede these attachments dont work I am very interested in 90 yamaha mods

[kellytheaker]

I happen to be reading this since all I could find was a 97 yamaha 75 and I could sure use some help bringing a bit more power out of this powerhead . I understand it has same block and such as the 85 and 90 so please forward what you need to do to make this 75 improve its baseline to the 90 specs . Thanks -

[coleindustries]

I happen to be reading this since all I could find was a 97 yamaha 75 and I could sure use some help bringing a bit more power out of this powerhead . I understand it has same block and such as the 85 and 90 so please forward what you need to do to make this 75 improve its baseline to the 90 specs . Thanks -

I cut and pasted the below info form somewhere on the internet, but it seems plausible. If you want to be sure, trawl through one of the online parts websites like megazip or boats.net or see what parts numbers change per year.
The carbs are exactly the same, it’s a common myth that the 90 has different carbs from the 75hp. The jetting is different but the venturi are the same. The physical differences are the 75hp had a low compression cylinder head and restricted exhaust tuner. 80hp had high compression head, restricted exhaust. 85hp low compression head, unrestricted exhaust. 90hp high compression head, unrestricted exhaust. The later 75hp may have had the high compression head fitted

[kellytheaker]

I appreciate the reply - still working on figuring this out . The carbs - square vs Round bowl is another question but possibly the square bowl are just on the premix motors like the 85 and such .
Another issue I have heard is when removing powerhead to do the exhaust tuner - the bolts are usually snap off . Hopefully when I do the changes to the tuner I can get them out reasonably with heat .

I cut and pasted the below info form somewhere on the internet, but it seems plausible. If you want to be sure, trawl through one of the online parts websites like megazip or boats.net or see what parts numbers change per year.
The carbs are exactly the same, it’s a common myth that the 90 has different carbs from the 75hp. The jetting is different but the venturi are the same. The physical differences are the 75hp had a low compression cylinder head and restricted exhaust tuner. 80hp had high compression head, restricted exhaust. 85hp low compression head, unrestricted exhaust. 90hp high compression head, unrestricted exhaust. The later 75hp may have had the high compression head fitted