The Helmsman 31' (Camano 31 plus 2,000 pounds) is beautiful - boarded one at Trawlerfest years ago, but appears to ride lower in the water, and in the pictures I've seen appear to throw a huge bow wake at higher speeds. The more powerful engines like some D4s and the D6 would probably comparable in weight to the TAMD41, and have lower speed handling comparable to the Camano/TAMD41. Look at Helmsman's pictures and other source videos of the H31', and see for yourself.
I had my Camano over 15kt once, and the handling was surprisingly bad/scary. I was empty on water, probably 3/4 full on fuel, new bottom paint. I checked out hydraulics, etc., to see what might have made the handling so awful, found no mechanical cause. So, I don't know if going for more power and speed is a great idea for a semi-displacement hull with a 25% displacement torpedo shaped deep keel - good luck with that. The wind resistance at speed is not exactly slippery, either - in no way designed for speed.
I love my Camano - so "form fits function" as a small coastal trawler, timeless nautical heritage look, great engine, etc. If I wanted more speed I think I'd trade for a Rum Runner Mainship type design, what some people call a "picnic boat" - faster with bigger single engine or twin diesels, but without the cabin space, long cruise comfort of the Camano - completely different function might require a completely different design below the waterline.
For cruising around the awesome inland rivers and sounds of North Carolina, the deep keel/skeg protected prop, pretty stable, very livable for moderate duration cruises Camano is a well balanced, flexible cruising boat. Not a very good fishing boat (exhaust, casting room, keel, etc), not fuel efficient above 8 knots, not a lot of other things, but perfect for our needs. Thanks, Bob Warman!
By the way, Camano ICW cruisers, take a detour and visit Edenton, Elizabeth City, Belhaven, Bath, New Bern, Oriental, Ocracoke, Washington NC, etc. Lovely smaller towns, some pre-revolutionary, most have low slip rates, ample anchoring grounds nearby, not crowded, great food, cruisers welcome. Prefer something more remote? Try Rose Bay - as close to untouched in 400 years as you can find. Perfect Camano cruising waters!