2004 Yamaha 60TLRD to 70HP conversion

[Jim311]

Does anybody know off the top of their head if it's a fairly straightforward conversion to make a Yamaha 60 two stroke into a 70? A quick scan of the carburetor parts shows different jets but I wanted to know if I'm missing something. Is it really that easy?

 

[Sea Rider]

For a nice conversion check if both models shares same CC power head, reed valves, carbs. If same CC can detune a 70 HP playing with time advance and carb synch, probably are different carbs, not just jets..

Happy Boating

 

[Jim311]

Judging from just the parts breakdown I've seen the carbs are basically the same other than the jets. Haven't been able to find a difference in any other place other than the jets. Maybe I'm missing something tho?

 

[99yam40]

think about it some.

does dumping Just more fuel make more HP?
I would think it would need more air to go with it.

Someone drilled out the jets in my C40 before I got hold of it.
took me a long time to find out why it had a high speed miss.
reeds might help
exhaust tuner might help some .
timing could do a lot too

check all parts of the 2 motors to compare

 

[Jim311]

In this case it certainly appears that more fuel DOES make more horsepower because all of the parts in the 70 are identical except for the carb jets. The block is the same, the intake is the same, the reeds are the same, literally nothing I can find is different other than the jets.

 

[Sea Rider]

Does the 60 and 70 HP motors shares same exact part number carb, if so, just change jets. If not need the larger 70 carb as definitely will have larger fuel passages compared to the restricted 60 HP one. Swapping jets will do nothing and only worsen correct motor performance.

Go for a prop maximization once have figured it out about carb differences. Check timing and carb synch, the 70 should have slight more of both if are fixed synched to each other or probably synch separately for correct full throttle operation.

Happy Boating