Re: vortec valve size
Have you ever driven this boat with the stock 260(230ish at the prop)? How did you come to the 320-330hp figure? Is there a speed you are tryng to achieve, or is this just a number that sounds good.
A "stock" vortec with a 4bbl will make about 320hp at the crank(290ish at the prop) and will be dead reliable for years to come. This will probably push that boat in the 60mph neighborhood.
I'm not sure that Liberator will gain all that much performance with a 320 crankshaft HP engine. It's a pretty heavy boat.
Mine did barely 60 with the (slightly) tricked 460 King Cobra (1.43:1 & 20p stainless) at 5000 rpm ...200 rpm over OMC's rated rpm........this was when the boat was new..... AND OMC claimed the engine did 340HP at the crank.
I thought it was somewhat slow out of the hole though. Once on plane it wasn't that bad I guess.
Even Mercruisers' EFI 6.2L (383?) is only rated at 320 prop hp...... and rated to run on 87 octane regular fuel.
Most of the (non-marine) machine shops that claim high HP values usually don't build engines that will do it at the RPM that most stern drives want to turn, they're carbureted AND you're probably not going to be able to run it on 87 octane gas. (a lot of lakes don't have higher octane gas so you'd have to haul it in)
When I went looking for a replacement engine and drive I considered a rather late model (2004) 5.7L MPI 300hp engine and (Bravo I) drive. I was worried that it would be slower out of the hole since it would have had less torque than the 460 King Cobra. The advantage might have been the fact that the Mercruiser 5.7/Bravo I would have been maybe 200lbs lighter. I don't think that would have made a big difference.
The only engine I would replace my current 454 with is a 502!
Cheers, Rick
