late 80's formula 271 sr1 twin 454mags what is top speed ?

Late 80's would be a 272 SR-1, which was 27' 2" to the transom, 28' 11" to the end of the platform. 271 came about in 92(?) at 27' 1" LOA. Anyways, they usually came with 330 hp 7.4's and top speed is generally 63-65 mph. I would expect 454 mags to be around 68-70 mph.

I had a 1989 272 with stock 330's except for Imco power flows
that was in the 67/68 range.

Rambunctious has an 89 272 with 330's. Bone stock. 64.9 on gps. Or so he says.....

mopower , did the imco exhaust make a difference with your top end speed ?

I have a 89 272SR1 with twin 454Mag Bravos (carbed) it ran 67mph on GPS totally stock engines and drives with non-labbed 3 blade props. Added Stainless Marine exhaust but it made no difference to the top speed. I added IMCO 2" shorties and went to 71mph on GPS with a good set of Hydromotive 4 blades.
I then added Whipples and went 84 with labbed Bravos.

26 Sonic,
Yeah, the Powerflows were good for about another mile to 1 1/2 per hour. It's hard to tell for sure with so many variables (temp , wind , humidity , load). But it was definitely better