This thread should help you get an idea.
Looking at buying a new boat. Would be very happy if you could give me some facts about top speed with 2 x 425HP and 2 x 580HP (Procharger, etc) on a Formula 353 Fastech.
85.3 with 525 EFI's. Try this article http://www.powerboatmagazine.com/2003tests/apr2.php.
If you take those numbers and plug them into the speed calulator for this boat on this webpage. http://www.go-fast.com/boat_speed_predictions.htm
for an 8600 lb boat doing 85.3 with 1000 hp (merc spec is 500hp per 525motor) and calculate the constant that gives you 250. Back calculate for your powers and it gives me.
2x425 = 79 mph
2x580 = 92 mph.
I'm not sure how linear this is but it should be pretty close. I'm assuming that when you get into the high 80's to low 90's there is a lot of friction that comes into account and the slope will be less linear.
Hope this helps.
Performance report from Formula says 73 mph (425's on salt, light chop, 80 degrees, 1/2 load, 28 Bravos, two way average). Hope this helps.
As strong as the 425's are, I'm kinda suprised there is a solid 6+mph between them and the 500...ya know?
We have just procharged a 2002 353 w/ a pair of 496 HO's, using the 5 lbs kit. The boat originally ran in the mid to high 70's. We are still making some adjustments, but are hitting mid 80's now. With any luck we will get a little more out of it. We are still playing with props. We went from 4 blade 28's, to 4 blade 34's on 1.5 ratios. WOT rpm is about right but getting on plane is a little more difficult. May try some 5 blades, or change ratio to 1.36's.
I went for a ride on a new 353 this spring with 525's. Sweet boat! With 4 adults and one child on fresh water we saw 84 on the GPS.
I will know next week if I have money for a new boat. We will travel to US before Christmas to look at four options - Formula 353 FT, Formula 383 FT, Phantom 34 Classic & Fountain 35 Lightning.
Not yet decided. But Formula 353 FT is a sweet boat. Reckon Formula 383 FT need a lot of power to run in high 80-ties. Do you know how much?
We have one of the best engine builders in Scandinavia here in town, and he told me that 550 HP is easy to get out of a Merc 502. Another option is to add a Procharger, etc, and get 580 HP at 3 psi. And reach mid 80-ties. Sweet and fun.
How much will Stelling boxes add to the speed (353 vs 382), and how much do you have to pay for them?
Cheeers, Toffen G
There is a 2000 model 353 here on Lake Norman with 500 EFI's and Whipples, with IMCO extremes and standoff boxes running mid 90's and very reliable.
The 353 is a sweet boat. We looked very close at them before making our last purchase.
Running 80 mph is fast and I always needed to feel a since of security that the boat will hold together. I raced the 35 fast tech and always felt like I had a solid boat under me even in 10' seas. Forumla Makes a fine boat. Jo
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