I have the 310 HP 7.4 MPIs with 28P 4 blade merc props and 1:65 drive ratio. Low 60s is consistent. 64-65 when the stars align just right. Ditto on the "does not like to go slow comment" It does not really get on top until 45+. It will run all day in the 50 to 55 range.

As mentioned by others, you have to use tabs and trim in in the 30 to 40 MPH range our it will tend to get unsettled easily and porpoise. The throttle is your friend on this boat - use it to drop and lift the bow to run smooth in chop or swells/wakes. A well timed blip of the throttle makes all the difference when riding the rough stuff. I think prop selection could help a lot with the ride issues, but I have not played around with that.

Am I happy with it? Yes. It has been rock solid & reliable. Would I like more power? Who doesn't - :drink:

Had a 97 with 502s and she went low 70s pretty much how she was loaded, good boat, just need a few more feet, you know what I'm talking about.

Since we are talking about 312's and speed, I have a question. On another site someone asked about the speed and desirability of a 312 with 496's and Duoprop Volvos.

My understanding is that any dual prop design is slower on top end than a single prop and that the Volvo Duoprop drive, in particular, has a poor underwater profile and is less fast than a Merc Bravo3. Is that correct?

I believe so, who's running a 312 with 496's what do you get?

Not sure about hydro-dynamics but some of those VP duo-prop drives are damn near bullet-proof. There is a guy in the upper bay running a pair of Volvo (Innovation) 600's with duo-props on a 382 and absolutely loves the set-up. I think he claims about 80 in it and a number of local verify it.