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Discussion Starter · #1 ·
Just drove 20hrs to go pick up my 27 fountain fever from michigan and i must say (after putting it in the water), it was worth every penny and every mile.

Very happy fountain owner. I've driven in several baja's from 22ft to 30ft and they really have nothing on the way this boat handles itself at high speed. Not to mention the speed itself.

Anyways, my question was speed related... Is 82mph good for a 750hp naturally aspirated 540 (chev) with a bravo XR drive and 26 stainless prop? Seems well matched, at that speed the engine is at its peak HP rpm according to the dyno sheets.

Here's a teaser pic for you guys:
 

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If it's a true 750hp, it seems a bit on the low side.

My boat ran 80.7 on gps with about 100 less hp , and your Fountain has a faster hull.

What kind of RPM are you spinning that 26 too ? I was running a labbed 26 to 5800 to get that speed.


Great looking boat !
 

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Speed (and prop pitch) seems low for that much HP.
If there was that much HP, I would think you'd be spinning a larger prop.
Nice boat!! Fountain makes a good - well designed product.
 

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Discussion Starter · #5 · (Edited)
Jakewood said:
The engine builder is top notch and you shouldnt find any surprises - the previous owners are very stand up people. Hate to see her leave the area...she certainly is a strong runner! Have fun and be safe!
was extremely well taken care of! nothing but good things to say about the previous owners ;)

I was just wondering though if the prop was properly matched because I have heard of less powerful fevers doing about 80mph and the engine really doesn't feel like its stressing to get there, it reaches that speed very quickly and gets on plane in no time at all, which implies that perhaps the prop is slightly smaller than that engine could spin. I think at 80mph it is around 5100rpm which is, by my calculations, only 11% prop slip -- pretty hard to beat.
 

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I agree it should be faster with that kind of power. But, 82 is nothing to sneeze at! You could try a bigger prop and see if you can more top speed out of it. What rpm do you run WFO?

Also, something to consider, many times engines are dynoed with dry dyno headers and no accessories. So, once in the boat the hp is down a little. But, like I said 80+ is a nice mark!

FYI, 80 mph with a 26 at 5100 is 5% slip. Even lower if it's a Bravo prop.
 

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Cool boat !!!!

82 is rockin' and rollin' !

A pump gas N/A 540 will take around 6500rpm or more to make 750hp. 5100rpm would be cruise speed for an engine like that.

Now, a 650hp 540 will be in mid 5k or more peak rpm range.

I'm not doubting builder as I have nothing in this, but I will doubt accuracy of dyno. Real data is important for knowing what you have and tuning the boat for it.

Again, I would love to have what you just picked up.
Hope you continue to enjoy it !

==============================

BTW: All that motor/dyno info I gave is all just my useless info and opinion.

I mentioned it NOT to take away from your new schweet boat, but quite the opposite reason, so that you do not get distracted from it and try to search for the extra 100hp that it possibly does not have. We see many people looking for something that's not there. Drive's you nutz and lessens the enjoyment for no reason.

Always take what I say with a grain of salt. :D :laugher:
 

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cfm said:
Didn't Shameless's Fountain have different gearing ? I think some of the newer Formula's do this too.
IF I remember right he had a 1.65 ratio which would make the slip even lower.

However, you bring up a good point as tg could have a 1.36 ratio with that kind of power which would be around 11-13% slip depending on the prop.

tg, post your gear ratio, WFO rpm and type of prop you have.

And as cfm said, I am definitely not taking anything away from your new boat! It looks like a great boat. I'm just trying to answer your question. :D
 

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Discussion Starter · #14 ·
The drive is a 1.36 and the engine does 748hp at 5400rpm with race gas, so just north of 600 with pump gas, which it has in it now.

The slip was calculated by scott at mercury racing to be 11% which he said was very good and would be hard to beat with this setup. I guess I should have checked the footnotes on the dyno sheet ;)

Anyways, Im just waiting for a nice quiet day to see what the real top end is...

Thanks for your help guys! If I pick up a blower for it ill be back on for some prop/drive ratio suggestions!
 

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TG,
I am just asking, not trying to slam or anything. It's a very cool boat but when you say 748hp on race gas and just over 600hp on pump gas. What exactly do you mean ? I'm no engine builder but I have never seen a motor gain over a 100hp with a change in octane, expecially if the motor is built for a particular octane. If it was build for race gas and you run pump gas you will hurt something. And if it's the other way around you won't gain anything.
Just curious.
 

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Discussion Starter · #18 ·
26scarab said:
TG,
I am just asking, not trying to slam or anything. It's a very cool boat but when you say 748hp on race gas and just over 600hp on pump gas. What exactly do you mean ? I'm no engine builder but I have never seen a motor gain over a 100hp with a change in octane, expecially if the motor is built for a particular octane. If it was build for race gas and you run pump gas you will hurt something. And if it's the other way around you won't gain anything.
Just curious.
I could post up the dyno sheets if you want to see it...
 

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It's up to you. I was just trying to help you with your original question. It's easy to say , no your speed is not right for that HP but there are many pieces to the puzzle.
Being that you most likely have a 1.36 ratio drive and are only spinning to 5100rpms makes your speed more understandable. :)
 

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Discussion Starter · #20 · (Edited)
Turns out its a 1.5 ratio drive, and now that I have a proper gps it does just north of 72 knots at 5800rpm with the drive out and trim set flat.

I must have been tracking the tach improperly before (guess I was looking at the water instead of the tach :pirate: )

Ran into a new problem though, the boat cuts out after running full out for about 40 seconds or so, it'll just cuts out and the engine drops down to a sputter and then stalls --- I wait 2 minutes or so and start it again she'll run normally until I try and push it again -- is this a tell tale sign of something? Fuel delivery or spark? The fuel pump doesn't sound too healthy when running before the engine starts. Guess the best way would be to test /af mixture in the exhaust while its cutting out... Weird though because it didn't do this before -- only after about a half-tank. Fuel filter/water separator maybe? ;\
 
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