312 fastech motor upgrade
03-20-2009, 02:50 AM
#2
Registered
Join Date: May 2004
Location: Phoenix, Az.
Posts: 97
Likes: 0
Received 0 Likes
on
0 Posts
There was a time I was considering re-powering my 312.
I called the factory and spoke with them about it.
They knew of one guy who had put 500 efi's in his but I don't recall if they gave me his contact info.
Give them a call.
I called the factory and spoke with them about it.
They knew of one guy who had put 500 efi's in his but I don't recall if they gave me his contact info.
Give them a call.
03-20-2009, 05:54 AM
#3
21 and 42 footers
Platinum Member
Local mechanic put them in a 312 about 3 years ago. Pulled 454mags that had 30P props (1.65 drives) and borrowed my 34P's. The boat owner loved it even though I thought the props were a little too big....they claimed the boat ran well past 80 but that was on the speedo. (probably was running 80 GPS)
03-20-2009, 02:04 PM
#5
21 and 42 footers
Platinum Member
The 500's can't weigh much more than the 7.4......but with 190 hp more per motor it's worth it!!! I had a 312 with 502 Mags, that boat was 8,000 dry from the factory......it can handle the weight of BBC's in the back!!
03-20-2009, 09:01 PM
#6
Registered
With that, 80 mph on a 31 foot swim platform boat aint great.
03-21-2009, 07:29 PM
#7
Registered
Join Date: Aug 2006
Location: Nashville, TN
Posts: 198
Likes: 0
Received 0 Likes
on
0 Posts
I just test drove a 312 with the base 7.4MPIs at Robert's today and had this very conversation regarding the 312 and bigger motors. The original BoatTest.com report of this hull with 2 X 385 HP 454 Mags they got 72.4 MPH on GPS at 5,100 RPM with 22" props and stock Bravo 1s- 1/2 fuel 3 persons. The base 7.4 310HP model we drove today got 64 MPH GPS with 2/3 fuel and 5 persons 70 degrees outside temp. Given this - The 500s or 525s will get you well into the 80's The factory runs the props deep - switch to short lower units which will raise the props and easily get you 4 to 5 mph with that change alone. I think that with a 496HO and shorty lowers you could get 80+. And yes - I bought the boat.
Last edited by rubadub; 03-21-2009 at 07:31 PM.
03-21-2009, 08:02 PM
#8
21 and 42 footers
Platinum Member
I just test drove a 312 with the base 7.4MPIs at Robert's today and had this very conversation regarding the 312 and bigger motors. The original BoatTest.com report of this hull with 2 X 385 HP 454 Mags they got 72.4 MPH on GPS at 5,100 RPM with 22" props and stock Bravo 1s- 1/2 fuel 3 persons. The base 7.4 310HP model we drove today got 64 MPH GPS with 2/3 fuel and 5 persons 70 degrees outside temp. Given this - The 500s or 525s will get you well into the 80's The factory runs the props deep - switch to short lower units which will raise the props and easily get you 4 to 5 mph with that change alone. I think that with a 496HO and shorty lowers you could get 80+. And yes - I bought the boat.
03-21-2009, 08:55 PM
#9
Registered
Thread Starter
Join Date: Feb 2008
Location: new hartford ct
Posts: 114
Likes: 0
Received 0 Likes
on
0 Posts
So you think its worth doing the swap I have 400hrs and stock motors still pur but as always more power would be nice. boat is very clean just don"t know about return on $ spent down the road.
03-21-2009, 09:03 PM
#10
21 and 42 footers
Platinum Member
your boat will be easier to sell later...but you'll never get what you put into it. (so what's the speed increase worth to YOU?)
