Evinrude G2 300 HP Outboards

by Bert
(West Australia)

WA Lobster Vessel

I have a 40 foot alloy lobster vessel, powered by two G2 300's it weighs about 7 Tonne and has a top speed of 40 knots in calm conditions. My problem is in rough conditions, wind speeds above 18 knots the props cavitate a fair bit. The answer is not lowering the engines.
The boat carries weight extremely well so I was thinking of replacing the outboards with a 450 HP diesel coupled to a Konrad 680 leg, this would add about 200 KG's to the back end which would be fine, the boat likes a bit of weight down the back. The other problem I am trying to eliminate is with the outboards, they can drop 400 revs in the troughs when travelling with a following sea. I would like to finish up with the same 25 knot cruise speed eliminate the cavitation by having a larger prop on the centre line instead of two smaller ones out from the centre, and reduce the rev loss in troughs with the higher torque of a diesel.
My question is would anyone have any Idea if I am on the right track, or would I encounter some other un for seen problem.

h.gomes@bigpond.com