Originally Posted by Rakuflames
I did not say I was moving at hull speed
under those circumstances.
No. what you said was "Until that 13 went belly up it moved the boat at near hull speed
if not against a current
." If the engine
moves the boat at "near hull
speed" in slack water
it will also move the boat at "near hull
speed" against a current
What you actually said implies that somehow an adverse current reduces your speed through the water
. I'm sure it was careless phrasing on your part rather than a misunderstanding of the principles involved, it is quite common to run into people who clearly misunderstand the effect of a current on boat speed: no effect on speed through the water, linear effect on speed over ground.
Your main point, of course, was that it didn't make sense to upgrade to a 30HP engine
. I agree completely. If you were satisfied with the 13HP's performance you will see some, but not much improvement going to a 20HP and a 30HP will likely yield little or no noticeable improvement over the 20.