500 HPs in a 312 fastech
 

I sold my Formula 312 this summer but a local mechanic I know is installing 500EFI's in a 312. The boat had the 454/330's and he is asking if I can suggest a prop pitch. Mine with 502 mags and 1.65 bravos (1.65 was standard) ran a 30 pitch 4 blade.
I seem to remember someone had put 500's in a 312 but don't remember who. Anyone familiar with a 312 that had the power upgraded? Looking for prop suggestions.

Re: 500 HPs in a 312 fastech
 

If it has 1.50 Bravos then I would start with a 32" Bravo 1.

Re: 500 HPs in a 312 fastech
 

1.65.....I asked if they were changing it to 1.5 and he was planning on discussing that with the owner.

Re: 500 HPs in a 312 fastech
 

Strongly suggest 1.50 gears. 1.65's will require way large props that will be very ineffieciant on a 312. We Procharged a 312 with 454 Mags several years ago and the 1.65's just would not work. We wound up with 1.50's and 34 Bravos labbed down to 33's.32's might be about right with 500's.

Re: 500 HPs in a 312 fastech
 

Did Phantom Chaos have 500s in his 312?

Re: 500 HPs in a 312 fastech
 

What kind of speeds will a 312 w/ 500's run? That seems like a lot of hp for a 31 Formula. How do they handle at those speeds?

Re: 500 HPs in a 312 fastech
 

The Procharged boat ran low 90's if I recall,but that was maybe 8 or 9 years ago,my memory is really bad. I do recall it handled well up to high 80's, a little loose above that,but customer ran it hard for several years with no issues.

Re: 500 HPs in a 312 fastech
 

I expect it will run near 80, maybe more on a "good" day. I remember reading somewhere that the 312 would chine walk from the low 70's to the high 70's then it's fine. Mine would chine walk at 72-73, but that's all I could get out of her.

Re: 500 HPs in a 312 fastech
 

I would have thought it would run north of 80. How much does the 312 weigh?

Re: 500 HPs in a 312 fastech
 

my old 311 had 502's and had 26's, straight hull older and heavier, I would start at at least 30's...

Re: 500 HPs in a 312 fastech
 

Depends on if your looking at the speedo or a GPS. :rolleyes: My 312 had stock 502 mags and was 8,000 lbs dry. Regularly saw 76-77 on the speedo, but the GPS was 71-73 (my bottom could have used slight work for better speed). Remember the 312 has a step, but it's a small single step. I figured the extra 55 HP per side will give it another 5-6 MPH. This guys boat should be ready soon.....guess we'll find out then.

Re: 500 HPs in a 312 fastech
 

The 312 is an entirely different boat than your old 311. A good 2 feet shorter, lighter, and looks more narrow at the bow (and the single step is only slightly beneficial). Every 312 I'm aware of had 1.65 drives and 30 pitch 4 blade props when powered by the 454 and 502 mags. I believe the 454/310 had 28 pitch but not sure.