The Super BP, was 100 cu. in. and 140 HP---

If they are 135s, that totals 810 hp. My twin Crusaders are 770 hp, not much less. I am sure the race boat was lightened up quite a bit, but maybe I will be pleasantly surprised next Spring.

I think you will find that the motors will be more efficient at 3500 rpm in that boat with the fuel injection. That may give you a cruise closer to 30MPH.

I would think the 502ci is a big torquey motor. Is it bad for them to run consistently at that high an rpm? I bet they are a lot thirstier at that speed too:-)

I found an original sales brochure on eBay for a 1969 35ft and it stated that the boat came standard with 325hp inboards. It also stated that it was the fastest 35 footer available. In those days though, 20-25 knots was fast for this big a boat.

Back in the days when all V-8's had carbies, the economy was ok up to about 3200 rpm but above that, the secondaries opened up and they started drinking heavily. Fuel injection has helped reduce that thirst surge in the mid range.

I agree with Katanna, you might see the hull running more efficiently with a bit more speed and leveled out. Load on the engines might be slightly less at 3500 rpm with the boat running nicely.

If you're leaving it in the water, a clean bottom is essential. Dirty bottom can cost you 5 mph easily and worst case scenario, you wouldn't even get on the plane!

Cool old boat, I'm sure you'll enjoy her.

RR

Thanks for the info. The boat is really in great shape. Hull was completely redone in 2008 with new barrier coated bottom, new topside paint, and all new running gear with the exception of the vee drives. The foredeck is rock solid. The teak cockpit decks are a full 3/4 inch thick (imagine that) and need a good refinish to get years of varnish off, but are in great shape. The only thing I am a bit dissappointed in is the aluminum framed windshield. That is going to need attention. Maybe Awlgrip it white. Would have been great if it was stainless. I did find some old paperwork in the boat. Appears that it was on Lake Michigan for much of it's life. That would explain why it has held up so well over the years.

Nice looking boat (stole a few of the photos from Yachtworld) but with antifoul and the V-drive shaft angle in a heavy boat, I think 40 mph would be a little optimistic. Keep that bottom as clean as you can.

RR

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Work out the prop pitch, rpm, ratio.

Isn't it reasonable to assume that the prop pitch/rpm ratio would have been correctly done at the time of the repower? What is the general rule of thumb for engine rpm at wide open throttle under full prop load?

Put me in the pool for a 38MPH top end, 24MPH at 3000 RPM.