285ssi

Hello everyone, I have just purchased a formula 312 2001 with 2x6.2mx engines, I want to change the engines for 2x454 mag I am wondering if someone has already done it? the holes for the exhaust arrive at the same position in the transom? do the engine mounts need to be changed? and my ration is 1.65 which pitch should I go 30? thank you for your answer and help

AllDodge

iTrader: (1)

The boat doesn't have enough width to install BB, only 8' 3"

285ssi

the boat left the factory with either 2x6.2 2x454 and 2x502 I do not understand that you say that

SabrToothSqrl

Yea, I think I've seen 312s for sale with 502s or 496s Seems like a big jump from a 350 or 377.

I just replaced the 350s in mine last winter, not much fun, but I'll follow along here for pics

t500hps

Wrong. Very few 312's built with small blocks. My 98 312 came with 502 mags. 454 MAGS with 1.65 came with 30's (502's did also). Boat should run LOW 70's with 454 MAGS. If you're considering regular 454's don't bother with the switch. I have no idea about engine mounts/exhaust lining up, etc.

MNHeat

Sell it and buy my 2003 with 496HO in it!

285ssi

no no I'm going to put 454 mags or 502 I was looking to find out if someone had already done the swap to know if the exhaust arrived at the same height etc

ph1971

iTrader: (1)

https://www.hardin-marine.com/Instru..._Locations.pdf

Unfortunately the locations are not the same, but it is pretty easy to move them. You will have to do a little glass work and gel.

285ssi

yes I understand what you are saying but take a good look at the 2 pictures the exhaust belows on a quite distinct angle

ph1971

iTrader: (1)

I didn’t realize you were going to run cast manifolds and risers. With that hose length you will be fine at sb locations. The motor mounts are probably a different story but I don’t know off hand. My factory big block boat left Formula with sbc exhaust spacing. It wasn’t an issue until I put on aftermarket exhaust that damn near touches the thru hulls.