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Need some engine help. 426

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Jennifer1985 said:
I was thinking Mercruisers, but also Volvo Penta's and Fords. Any reason why I would go with one over the other?
Quality of Volvo Penta over that of Merc.

And how much power would I need to get this boat up to the 70mph range?
Why not simply sell this one, and buy a boat that was factory built to perform up to your expectations?

Also, How hard would it be or how expensive would it be to take 2 5.7L V8 engines from like a Camaro and convert them into marine engines?
Not difficult at all..... but DO NOT use the GM full dished pistons!

I know I can 600 to 700HP out of those pretty easy.
I don't believe that you are quite understanding the limitations when an Engine is put into a working Marine invironment, and in particular a boat of approximately 26 foot in length and of this weight!

A 600 hp SBC will self destruct in a boat of these specs.


Anyone ever thought about doing diesels in these since a boat needs torque and not HP?

Would it be worth my time to rebuild this engine and convert it to stern drive and get a second one to match it?

What do you think the MPG would be on this boat with twin 426's and the twin 5.7LV8's and the Mercruisers?

You're asking questions that we cannot answer for you!

Thanks again for all your advice from everyone. I was in the Navy and know a lot about boats and I love the deep vee hull like you guys were saying. Almost half the reason I chose it. Also because I like the look and style of it. I know it's a heavy boat, but right now it's completely gutted and weighs like 3000lbs. Once I rebuild it'll be back up to like 5000lbs. And like I said, my plan isn't to sell this boat for many, many years. I listen to my spouse nag about it already, so the last thing I am gonna do is rebuild and sell for a loss or to break even. I would never hear the end of it. Right now though, my main concern is getting it water ready. So the plan is:
1. Get current motor running to enjoy until I can.......
2. Re-power the boat with new engines and stern drives
3. New Flooring
4. New Steering Wheel and Cables
5. New Interior
6. Seating
7. Kitchenette and Bathroom
8. New Covers
Click to expand...
 
This will be a project over time and for turning I would never try to take a turn in a boat at 70mph unless it was a race boat. I have 2 reasons for going that fast. Since it's a blank slate, I am building it to do a lot more. Like I live in Cleveland right now. I want the speed to be able to go to Cedar Point, Detroit and Niagara Falls quickly. Then, I plan on moving to Florida, so I am going to be buying saltwater engines. This way they can be used in both ocean and freshwater applications. But I will be installing 2 150 Gallon gas tanks that can feed off each other. This way I can run just the single 150gal when I am doing smaller things like coastal fishing or just having some fun. Then use both tanks to make runs to like Key West, Cuba, Jamaica, Panama City(Florida), Deep Gulf Fishing and then trailering over to the Atlantic side for some real deep sea fishing...
 
Ricardo, I think your answers are great and you are very informative. I guess I am looking for a little more detail so I do have a better understanding. In the Navy I was a hull tech and an EOD. So I know about the hulls of a ship and about blowing things up. I'm not a great mechanic, but I can get things done and learn very easily. I like the look, style, reliability and performance of the Formula boat. I don't want to give it up. Plus, this is my project. Something to keep me busy during down times, like this winter and I don't have $30,000 up front or credit for a loan to go get a new or used running perfect boat. I am re-building this one out of blood, sweat, tears, love and savings. My goal is to put money away and use tax returns and bonuses to rebuild this boat. I know it's not ideal, but it's what I want to do.

In this instance though, I guess I would have to ask, what would your recommendations be for replacement engines and at what ratings? 70mph is necessary, just a wish. If I can't achieve it safely, then I won't attempt it. But I also don't want to go with a single 260HP engine that will only get me 35mph either. I definitely need to be able to run 60mph or more. Thanks again.
 
Also does anyone know what this bolt is called and what size it is on a 426 so I can get the darn thing off? I have circled it in pink in the picture...74600502.jpg
 
Jennifer1985 said:
This will be a project over time and for turning I would never try to take a turn in a boat at 70mph unless it was a race boat. I have 2 reasons for going that fast. Since it's a blank slate, I am building it to do a lot more. Like I live in Cleveland right now. I want the speed to be able to go to Cedar Point, Detroit and Niagara Falls quickly. Then, I plan on moving to Florida, so I am going to be buying saltwater engines. This way they can be used in both ocean and freshwater applications. But I will be installing 2 150 Gallon gas tanks that can feed off each other. This way I can run just the single 150gal when I am doing smaller things like coastal fishing or just having some fun. Then use both tanks to make runs to like Key West, Cuba, Jamaica, Panama City(Florida), Deep Gulf Fishing and then trailering over to the Atlantic side for some real deep sea fishing...
Click to expand...


It's not a question of turning, its a question of safety, and actually going straight over 60 MPH the loads on the outdrive are very high, and the possibility of failure of any steering component is a definite possibility with catastrophic results. External hydraulic steering is mandatory IMO. Just think about losing steering at 60 MPH or faster, then the engine torque causes the outdrives to violently turn to full lock left or right. External steering mounts directly to aft portion of the stern drive, eliminating all the links in the chain between the steering cable and the propeller, as well as the cable and pulley system itself. As for your thoughts on fuel tanks, balance of the boat is critical in good handling, and 150 Lbs of Gasoline is 900 Lbs, and I don't believe there is enough room to mount 2 150 gallon tanks centered over the Keel in your boat. If they are off center, filling and running off of one will cause the boat to list dramatically, and mounting them front and rear will cause issues getting on plane and seaworthiness. Manufacturers don't just throw parts in a boat willy nilly, They design and test them to get as close to the ideal balance point, and even after all that there are times they don't get it correct. If you really like the 255 your best bet is to scrap all the inboard pieces, fix the keel of the boat, and reinstall twin stern drives. Two small block chevy 350s making about 275-300 HP with Volvo 280 drives will get you a nice dependable boat that will run 50-55 MPH on a reasonable budget (12-15000$ if you scrounge around) The next step up, getting a reliable 350-400HP from the motors will add another 5000$ to your Budget and get you 60 MPH. Then reinstall a set of replacement fuel tanks in the stock location. Don't try to reinvent the wheel on a 40 year old hull design. Furthermore a 25' boat no matter how seaworthy its design is pretty damn small to make runs across the Gulf Stream to Jamaica or Cuba, Let alone the Great Lakes. I'm not saying it can't be done, but in the words of Martin Brody, "You're gonna need a bigger boat" Guys with unlimited budgets have a hard time making it to Cuba or Jamaica in a power boat, let alone at 70 MPH
 
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