42 fountain straight bottom 100 mph
12-18-2009, 09:37 AM
#41
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12-18-2009, 10:12 AM
#42
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Efi Sc
The boat has stock EFI motors. Put them on a dyno and they are stong as far as 525s go. Its my understanding that the 525s hp out put can vary signifcantly, got lucky and got a strong pair. These have not been tweeked or modified in any way. I purchased them direct from Mercury. The boat is a race/poker run version, no cabin, had the bottom checked but not blue printed. The boat dry weighs about 7300-7400lbs. I believe it was vacuum bagged epoxy which is unusual for a 38 Fountain. The x seems to be about a 1/2" higher than other 38s out there. I run the spacer to help preserve the xr drives. Jeff formally with Mercury X site did/does my drives and he is awesome. I think his drive set up as well as the higher x contributes to the boats performance?
12-18-2009, 04:06 PM
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Thanks we spent some time and money figuring out what works and what does not work. The 38 ( at least mine) is very sensitive to trim. A great set up is useless if you can't trim and drive the boat to its potential. I had a 38 stepped lightning with a full cabin and a pair of 500s and it would "only" run 84mph strait from the factory. Its fun running poker runs in the little 38 with 525s with the big horse power boats and finishing near the front. The 525s with proper service just don't break. Bravos are a whole different story they are great in the smoother stuff, but the torqe they produce is tough on them in the big stuff
Racer
12-19-2009, 04:31 PM
#47
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I am willing to bet if you run the numbers on the new 40 epoxy Fountain race boats you will find they are as efficient or more efficient than mine. I have driven one with stock 525s and 6 drives at 102 mph without ideal props and set up. I am sure the boat with fuel and a driver and throttleman was atleast 8,200 lbs. I realize the formula is kinda generic and probably an average of some sort, but I wonder how accurate it is based on recent technology such as stepped hulls, superb props, ect ect. I am not just talking about Fountain , but Outerlimits, Cig, and other Manufacturers as well.
12-19-2009, 10:23 PM
#48
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The formula is generic but it works with any boat and any combination. If you know the weight, HP and top speed it will tell you the hull efficiency. Because it is mathematical, if you know any three, you can calculate/determine/predict the fourth. This is the formula:
Hull efficiency (220, 252, 275, etc)
__________ (divided by)
Total weight = MPH
_______ (the sq root of the total
weight divided by HP)
HP
This is what Mercury uses. I doubt they made it up, I believe it is SOP marine engineering.
It is pretty easy to see that many/most HP boaters spend way too time, effort and $ in the engine compartment.
On Monday, I will draw the formula, scan and post.
Ben
Hull efficiency (220, 252, 275, etc)
__________ (divided by)
Total weight = MPH
_______ (the sq root of the total
weight divided by HP)
HP
This is what Mercury uses. I doubt they made it up, I believe it is SOP marine engineering.
It is pretty easy to see that many/most HP boaters spend way too time, effort and $ in the engine compartment.
On Monday, I will draw the formula, scan and post.
Ben
12-19-2009, 10:45 PM
#49
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well I have it in my head with proper set up drive height and under 10,000 lbs with triple 700 hp (propshaft) I can go 100 think this sounds doable?
that would be a constant of 207
that would be a constant of 207
