..for a reccomendation. The subject is a 1979 Formula 255 Liberator, The hull is a classic 24* deep vee with a dry weight weight of 5500 and 125 gallons of fuel. The power is twin modern era SBC's making 400 HP and 435 # of TQ. Maximum RPM is about 5500 RPM with the TQ peak at 3200. Drives are Bravo I with 1.5 gearing. Drive height is OEM.

I am planning on starting with basic 21" stainless Mercruiser props to break the engines in for 8~10 hours while taking it easy...not pushing them too much on the low or high end. After that I will be looking to make a move to a more permanent solution. This is my first stern drive project in 20 years...with my most recent experience being with inboard cruisers in the 35'~40' range.

Most of my boating will be coastal SE Florida with occasional runs to the near by Bahamas. I'm looking for reliable high speed cruising with decent low speed manners.

What do these old "Heavy 'Birds" respond best to from today's technology?

Based on what is available today, what is your calculated best choice for my combination?

Thanks in advance.

Counter rotating drives? If yes, are you spinning them in or out?
My guess is that you'd want to try Merc Mirage plus in the 23p range.

Pat...thanks for your response. The drives are in their original location so without measuring them I am guessing they are deep by today's standards. Understanding that the Bravo's allow me rotation selection, I may choose to turn them out. Is there an advantage either way? My bigger boats always turned out...I never thought about turning them in.

I have read a bit about the Mirage Plus and agree that it could be a match for my rig. In your experience, does the Mirage Plus have a lot of bite in rough, aerated water? My last performance boat was an '86 Formula 272 with old style cleaver props...which were notorious for cavitation in rough going off shore.

The closest boat I've owned to yours was a 78 28' Cig with TRS drives. It had cleavers and did run fastest with thoses.
We also ran Mirage plus and Turbo Vectors 3 blades and they were better in the rough. Spinning them out the boat handled better but she ran faster spinning them in.
What drives did the boat have originally?

This 255 had pre- Alpha No 1 drives, 260 horse 350's. in good tune it topped out with a light load about 60~65 and ran 50 in a cruise without too much effort. I was running standard stainless 21" Mercruiser old style props.

john,,what i found to work the best(back in the day) were the lazerII props..

Try a 21p Revolution 4 blade. You wont be sorry.

23 pitch laser II might be worth trying. With that much power, you might need more pitch than 23. I just happen to have a pair of laser II 23 props sitting on the shelf that I will not need back until May at the earliest! You could try those.

Let me know if you want to try them.

Brian

Thanks Brian...I might do that in a few weeks. Did you run them on your 272 and if so what was your experience?

No, I only ran my 21 pitch 4 blade aluminum props the three times I was out. It would spin those easily, so the 23p 3 blade stainless laser's should work nicely. You have quite a bit more HP than I do also.

One problem I just thought of, I have standard Alpha's so they are both RH props. You would not be able to CR them. It would still allow you to test the performance of them, but the handling would not be the same. If you want to test them, shoot me your address. I would be curious to see how they perform on your boat and then on my 272 verse what prop you end up going with. Would be interesting.

Brian