I said I'd write this morning, but got caught up with work at work oddly enough so couldn't
The 140 Suzuki 4-stroke on the back of the 6m Humber Destroyer is a good combination I reckon. When I first wrote to Humber at about this time last year (in speculative mode), I asked them for costings of a reasonably priced 6m rib (mentioned the Destroyer), and a suitable engine to go on the back (4-stroke pref).
They came back with the 6m Destroyer, with Suzuki 140 4-stroke package including trailer and everything. At the time, I had only read reviews of the 140 unit, which had come out quite well.
If I remember right, sometime beginning of last year when it was new out, they tested the Suzuki 140 on the back of an Ocean Extreme 7m Humber in RIB International - I don't recall a bad word said about it.
Anyhow, to actually see the engine, I trundled down to the Southampton boat show, saw a 225 Honda with water trickling out the back, and thought 'wow'. I think about 3 boats across was a zodiac rib with twin suzuki 140 4-strokes on the back, also with water trickling out the back.... but where was the noise?! Both units were running, but they were pretty much silent.
I then went on to have a look at the Humber Ocean Pro which had a 115 Suzuki on the back, equally as quiet. Unfortunately, doing a trial was out of the question cos of the low speed limit down there in soton, so I took everyone's word for it being good
Eventually ordered the 6m Destroyer, with 140 4-stoke from Humber, and took delivery in December last year. After a painfully cold run in time, the engine didn't reach max revs, but now, I have changed to stainless, I am reaching nearly 6000 revs, and maxing out at 43knots with trim right out. Obviously you don't go flying everywhere at that speed, but the boat will cruise quite nicely at 26 knots using about 4500revs on the engine (which Suzuki reckon is the most fuel efficient).
I did my powerboat L1 and L2 2 day course with a local diver charter company on a Destroyer 7m rib I think it was, with Johnson 200hp venom engine - I can never forget the power, and the dry ride, even in the rough stuff.
An alternative engine I'd guess now could be the Yamaha 150 4-stoke engine which is new out this year.
Bit of a long'n that - if you want any more info, feel free to pm or e-mail me.