[Fr. Frank]

Originally Posted by Terry England

...
Pontiac used that 250 CI block and built an aluminum Single overhead cam version with better carb's and put some in Firebirds and their LaMans' or Tempests. That very light motor would make 250 HP, I think out of the box.

Mercruiser DID make a 250hp version of this motor for racing purposes. It was called, strangely enough, the 250/250. used through-hull exhaust and was coupled with the M/R drive. Carburetor was a marinized Rochester Quadrajet, but I don't know what the cfm rating was.

I've only seen two boats with this power setup.
John Allmand made a 19' back in 1968 for the offshore racing circuit (yes, intended to compete with the 21' SeaCraft), that was powered with a single 250hp 250ci motor. I don't think he ever finished a major race. We had this boat collecting dust in the boat barn, and I only saw it taken down once for someone to take photos of it.

Formula made the '69-70 23' with twin 250hp 250ci I-6 Mercruisers and they too, were, in fact, rated at 250hp each. Top speed was in the high 50mph range. We got one of these in at Waterway Marina in Palm Beach Gardens back in '84 with a bad motor, and we sent it across the street to Frank Brown Marine. As I recall, they gave it a new long-block because the motor had ingested water through the exhaust. I recall one of the mechanics saying he got it up to 58 mph during "testing".