finally, I haven't ruled out the 150 yet so Ibwet, what do you use your boat for? is it mainly cruising? have you pulled any skiiers/toys?
Proportionally the larger the boat engine combo is, the smaller as percentage the skier becomes. I learned to ski behind a SR4, with a 60hp 2 stroke, so technique needed to be good, we changed props travelling /Skiing as has been suggested already.
I've never tried behind a Suz 140 but even if the 128hp theory is true, I can't see there being any issues (even on a mono) up to 6mtrs.
My boat has pulled a mono skier out with three adults up, obviously slower than just me aboard, but it's only a marginal difference. I've settled on a 25" prop, I've now never feel the need to change it for anything.
We use it mainly for island hoping pub to pub
kids, water toys, back up to another boat. Its covered trips of over 200 nm and never missed a beat
There was another 5.85 owner launching in the marina with the 140, we swapped over, the 140 was sweet and smooth but both of us thought the step down in go was marked.
I think the extra torque is allowing me to run the larger prop that levels out the consumption, the only time I use full power occasionally or to show off, as it chine walks.
I've never wanted for more power, that’s worth a lot on it's own. So as far as I'm concerned the only issue is you've got is weight.