Yamaha Outboards: 4 stroke 70hp vs. 2 stroke 90 hp

[midsized johnson]

My boat is perfectly suited for the 90 two stroke. It's a 15 foot scooter with a tunnel bottom made to run skinny. Mine is powered with a 115 Johnson which is considerably overpowered, but holds okay. I'm looking to go lighter weight for a shallower drifting and hole shot.
A boat builder friend of mine heard that the 70 four stroke has almost the "balls" of the 90, due to increased torque, but with better fuel economy. Of interest to me is the lightness of the 70, only 255 lbs, vs my 115's 335 +/-.
He built a boat like mine that was powered with the 70 and was impressed with its performance. I know how well they run with the 90 and I wasn't there for the sea-trial, so I'm just wondering if anyone has an opinion or heard anything along these lines.

 

[robert graham]

A 90HP Yamaha 2 stroke could be more power than you need on a 15 ft. boat....seems like a 70HP 2 stroke might be the best power/weight mixture.....

 

[midsized johnson]

No Title

That may be the case, but I'm really curious if anyone has any idea how the Yamaha 70hp four strokes stacks up against the 90 two stroke. Very similar weight between the two.

 

[99yam40]

http://yamahaoutboards.com/owner-res...ance-bulletins

See if you can find any helpful info on here.

Being 20 less HP I am sure they use different props, but maybe you can find a boat set up with a F70 and one with a 90 2 stroke so you can compare the 2's performances on same hull

 

[midsized johnson]

Thanks 99, pretty interesting reading. Looking into the 70 today to see if the dealer can give me a good enough deal to give it a go.