Simon is pretty much on the money here, except that I think the V6 300 should
ONLY be run on Premium (Jim can confirm if this is correct or not). The actual tested power outputs for the Yams by the US EPA are 288 vs 264 Hp for the 300 vs 250 respectively (refer attached). Note that the 300 produces max torque at 5000 rpm, 500rpm above that for the 250hp. Your current 3.3L 225 provides 221hp (also from EPA data).
At WOT a simple calculation tells us that the extra 24 hp will give us a theoretical "SQRT(288/264) = 1.044" = a 4.4% increase in top end speed, all things being equal (i.e. prop efficiency, boat/engine setup, conditions etc). What we can't compare is how they perform at the important mid-range, as torque curves are a big secret in this industry. However Simon's comparison above is obviously a good guide.
At WOT the 300 will burn ~100L/h while the 250 will burn ~90 L/h.
I do like the new 300 V6, and I have done plenty of hours in a mates 685 with one - and it is indeed a sweet donk, however if I were choosing a donk for the 685 I would go the 250 every time as (IMHO) the additional 24hp is not worth it in this case.
Your case is a different kettle of fish again, as the 2601 is a fair lump of a boat. Knowing about your required/normal loading (from your previous threads) I would definitely be looking at all options, '250' and '300' and '300+' classes, all colours, (and I am a Yamaha man
![Grin](http://www.ausfish.com.au/yabbfiles/Templates/Forum/default/Original%20Smilies/grin.gif)
), including the 350 V8. Check out THT, thousands more 2601's over there than here, and I am sure there are relevant threads to check out re power options. Good luck.
Cheers
Brendon