It depends on a number of factors but my Tornado 5mtr does about 23kts flat out with a 60 merc 2S with 13" pitch prop, when I put on the 14" prop it has a bit higher top speed.
Things like hull design, load, prop pitch will all make a significant difference.
My 4.7m zodiac will do 39mph according to the gamin 550 with a mariner 60 4 stroke two up and full fuel load of 45litre at WOT. Your Humber should do something similar.
Weight will play a huge differnece in a boat of that size.
Mine was passing 31 Knts before the engine expired (nowhere near WOT). 14" prop with a skinny leg clamshell on the back (gearbox & leg size equivalent to most 30s these days) and the whole lot (not including me) clocks in at 420 Kg.
I guess you are looking at buying one? If so, borrow a handheld GPS & ask for a test run...
Just out of intrest do you do top speed in, speed over the ground? or speed over the water?
depends! If your going with the tide official FIBnet procedure is to measure it as speed over ground; for maximum performance reporting you should record your speed in "mph" but report the mph value as being in knots too
depends! If your going with the tide official FIBnet procedure is to measure it as speed over ground; for maximum performance reporting you should record your speed in "mph" but report the mph value as being in knots too
You can get a bloody good figure by leaving the GPS on while the boat is on the trailer
Actually with a maximum road speed limit here of 40mph on main roads I think that could count as incriminating evidence "No officer honest it was 54mph on the water"
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A Boat is a hole in the water, surrounded by fibreglass, into which you throw money...
I have a 5 metre assault with a 60hp stroke mariner.......... top speed 34mph according to the garmin 550.... this me (16stone) plus 2 x 25litre fuel tanks...
"No officer honest it was 54mph on the water" 
