I'm a bit late joining in on this... Hardly been on Ribnet for ages... Too busy with work alas!
Anyway, 32 LPH is absolutely awful. I've done several checks on mine and it always comes out around 10 LPH for an average cruise.
I get 30 knots at 4,000 revs with a 23" prop and a full tank of fuel, and about 32knots at 4,200 revs as the fuel gets lower. Mine is a 6.3 Mtr boat weighing around 1.2 tonnes... (Those are maximum speeds... I usually cruise at about 23 knots)
So I would take a look at your setup.
Best of luck,