Hmmm. 405HP and 450 Ft-lbs out of 383 cid sounds more like a diesel than a gas motor. I've never seen anything like that ratio of ft-lbs/$ in a legitimate marine set-up before. Adding the exhaust manifolds, tstat housing and raw water pump is a grand or so (?). I'm bookmarking that one for the future... A couple of gallons of octane booster could fix the problem with 91.

That kind of torque is well past what is recommended for an Alpha and I think it's a bit past a basic Bravo spec. It may be close to the spec limit for a Bravo 1X... That said, Seacrafts are light enough that drives seem to last a long time if you're nice to them.

The 383 stroker mpi is a nice motor but I think it is a bit much for a 23 seacraft. My brother has one in his and it is nice but I think the 6.2mpi 320hp instead of the 383mpi with 350hp is just as good and prob a little more economical.

Island Trader has a 383 stroker in his 1964 21'. It runs real good with a ton of mid range torque/Power. I think his WOT is 50+

Here is the 383mpi stroker.

Decided to put a 383 stroker in my 73 Tsunami when I restored her last year when she turned 40. It is paired with a bravo one and will hit 52-53mph top end and cruises at 28knots. Had a 350mag prior and although it was more economical it is a totally different boat since dropping in the 383.

http://www.classicseacraft.com/commu...pictureid=1681

http://www.classicseacraft.com/commu...pictureid=1682

How is the fuel economy cruising at 28kts?

On the 21 at 28 knots my burn rate is around 9.2 gals /hour...or 3.2 miles/gal.

WOT...25 gal/hr.

Unfortunately I do not have a floscan on boat, but figure burn rate is about 2 miles per gallon based on total burn. The 350 mag was definitely a little better on fuel for me compared to the 383 but not noticeably worse. Was originally thinking of going with an outboard and bracket, but am very comfortable with the performance of the boat paired with a mercruiser with bravo one drive.

Is the outdrive capable of handling the torque over the LONG term ?

Bravo 1 is good for about 500-550HP for a couple of thousand hours if properly operated and maintained (for the newer 'sweptback' design). Older ones slightly less. The real limit is in torque though. Not too many small blocks can break them. Do a bunch of exits/re-entrys with the throttle improperly managed and you can break anything though.