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Discussion Starter #1
Say ,same motor, going from an 18' to 21' ? Same ? I know everyone is going to say more info for your combo...but I'm wondering in general.
 

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E-7 Sheepdog (ret)
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Say ,same motor, going from an 18' to 21' ? Same ? I know everyone is going to say more info for your combo...but I'm wondering in general.
IMO, in general, larger heavier boats need a larger impeller for the greater push at the same engine speeds.

You also need the motor to drive the impeller.
 

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About 500' AGL
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It doesn't matter what size the boat is....you just want the motor to be able to spin the impeller where the motor makes the most power.
 

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It doesn't matter what size the boat is....you just want the motor to be able to spin the impeller where the motor makes the most power.
Is that the most HP or torque...? :D
And how does one know if they didn't pre dyno the engine :)sphss
 

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Discussion Starter #8
I've been told my engine makes peak hp at 6500 rpms'.s I did'nt think my cam was that large. If it helps my motor would spin the panther to almost 6k,same motor- everything, spun a (energized) "b" cut to 5300 ish. Now I have a little larger boat and a berkly ab, and I was thinking with a heavier boat, maybe I'd need to spin her a little higher. Sounds like smokin is thinking the opposite(sp?), and mud pumper is thinking what ever cut would run best in an 18 is the one you'd want in a 21.:)coffee
 

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Glendale Arizona
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I've been told my engine makes peak hp at 6500 rpms'.s I didn't think my cam was that large. If it helps my motor would spin the panther to almost 6k,same motor- everything, spun a (energized) "b" cut to 5300 ish. Now I have a little larger boat and a Berkeley ab, and I was thinking with a heavier boat, maybe I'd need to spin her a little higher. Sounds like smokin is thinking the opposite(sp?), and mud pumper is thinking what ever cut would run best in an 18 is the one you'd want in a 21.:)coffee
Although it might be true that max hp is at 6500 rpm it seems the question would be how much more at 6500 vs. 6000 or even 5800. If it's only 10-20 hp more it wouldn't really be worth it to spin it that high. The hp numbers (10-20) are arbitrary, but you get the gist.
 

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Although it might be true that max hp is at 6500 rpm it seems the question would be how much more at 6500 vs. 6000 or even 5800. If it's only 10-20 hp more it wouldn't really be worth it to spin it that high. The hp numbers (10-20) are arbitrary, but you get the gist.
Excellent point. My motor made 25 more hp at 6800 than at 6200, Im spinning a Heritage A to 5800(bigger than a berk A). At 5800im making 775 hp(YES, Sleeper CP, that is corrected HP!:|err)... so Im leaving 25 hp on the table as I see it. I like the accelleration Im getting with my impeller so Ill probably just leave it the way it is.

Running this power in an 18 foot boat with a Jacuzzi B was pretty sickening...Id love to see what it would have been like with an A.

For a 21 I'd keep the bigger impeller. A heavier boat will need the increased efficiency unless you have lots of power to spare.
 

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I've been told my engine makes peak hp at 6500 rpms'.s I did'nt think my cam was that large. If it helps my motor would spin the panther to almost 6k,
The panther RPM does not transfer over...For whatever reason you can spin those things to the moon and from what I have seen it doesn't increase speed.
 

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Resident Ford Nut
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I've been told my engine makes peak hp at 6500 rpms'.s I did'nt think my cam was that large. If it helps my motor would spin the panther to almost 6k,same motor- everything, spun a (energized) "b" cut to 5300 ish. Now I have a little larger boat and a berkly ab, and I was thinking with a heavier boat, maybe I'd need to spin her a little higher. Sounds like smokin is thinking the opposite(sp?), and mud pumper is thinking what ever cut would run best in an 18 is the one you'd want in a 21.:)coffee
Is this a rec boat or a race boat ? If you do a lot of cruising with it I'd go with a larger impeller. Kind of like having 3.73 (a/b) gear's vs 4.54's (C) This all goes out the window if you have a MPD of simular full race prep'd pump.

As far as your engine HP, post some spec's on it. There are a few guy's here that have desk-top dyno's and can give you a close number. Max Power at 6,500 ... how much does it make ?

Edit: There is a strange balance between impeller load vs rpm and fuel usage. A more powerful engine spinning a smaller impeller at a higher rpm more than likely will have less load on it than a less hp engine spinning a larger impeller at a lower rpm ( at cruise rpm's) and the larger engine will use less fuel cruising. It can also be said that the same engine spinning a smaller impeller may do the same thing , use less fuel. You just have to find the balance.

Sleeper CP :D
 

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Resident Ford Nut
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Excellent point. My motor made 25 more hp at 6800 than at 6200, Im spinning a Heritage A to 5800(bigger than a berk A). At 5800im making 775 hp(YES, Sleeper CP, that is corrected HP!:|err)..QUOTE]

Just wondering, how much more power did it make at 6,800 vs 5,800 ? And do you run nitrous on it ? At 5,800 are you spinning at your max trq #.?

I ran a larger impeller for yrs and lugged the engine, but more like at 5,300 vs your 5,800. Once I brought it up to 5,800 I said " damn should have done this yrs ago." The throttle response was just awsome. Now it's reving 6,200 off the bottle and is even better. Two weeks ago with two of us in the boat with cooler's and skiies and full tanks 4,000 rpm's 52 mph cruise speed.

Sleeper CP
 

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Discussion Starter #14
Thanks guys. My tach was junk the only times I've been in the water, I was hoping to hit the water today(with my new tach) ,but I don't think it's going to happen, I'd be suprised if I'm getting past 5k. As far as boat just pleasure-go fast (or at least trying to) not race or anything. Motor specs are 427 bbc,crower 1206 hyd. flat bumpity stick, brodix bb2plus heads cc'd at 116, 800 dp on a vic jr.compression just over 11.5 to 1. steel crank and dimple rods if they matter. oh and exaust is tt bassets.
 

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Excellent point. My motor made 25 more hp at 6800 than at 6200, Im spinning a Heritage A to 5800(bigger than a berk A). At 5800im making 775 hp(YES, Sleeper CP, that is corrected HP!:|err)..QUOTE]

Just wondering, how much more power did it make at 6,800 vs 5,800 ? And do you run nitrous on it ? At 5,800 are you spinning at your max trq #.?

I ran a larger impeller for yrs and lugged the engine, but more like at 5,300 vs your 5,800. Once I brought it up to 5,800 I said " damn should have done this yrs ago." The throttle response was just awsome. Now it's reving 6,200 off the bottle and is even better. Two weeks ago with two of us in the boat with cooler's and skiies and full tanks 4,000 rpm's 52 mph cruise speed.

Sleeper CP

Makes 50 more hp a 6800 versus 5800(825 versus 775). Max torque is at 5300(709 lb/ft), but at 5800 rpm im over 695 lb/ft...No nitrous but Im thinking hard about it. My reason for not reving to 6800 is I'd rather not beat it to death. I need the motor to last a long time so I think keeping the R's down will help that.
 

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I'm baaaaack...
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Man, you guys lost me. I'm running a 461 Olds, soon to be 464, it went 67 GPS flat out at just under 5,000, but took a while to get there. The tag on the Berkley JC case says it is an "A".

I recammed it a few years back and that woke it up a bit. Now, due to burned rods, I'm redoing it. Higher compression forged pistons, maybe Edelbrock heads, bigger cam, etc. Should I change impellers for the new motor? Or wait?
 

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TrynPas asks...
"What is considered a 'larger impeller'? an A or B? How far do they go both directions? (AA-C?)"

Not sure of all sizes but, I do know there is a AAA. I bought one and want to try it with my 14-71 blown 541" I am building for my '74 Rogers.
The bowl had to be machined to fit the impeller.
Steve
 

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Sit N' Spin
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What is considered a 'larger impeller'? an A or B? How far do they go both directions? (AA-C?)
The lower the letter, the larger the impeller. It takes more horsepower to spin an A to 5500 RPM than it does to spin a B impeller to 5500 RPM. However, the A will also move more water at 5500 RPM than a B will at 5500 RPM, which loads the engine down more, which is why the higher horsepower requirement to spin to the same RPM.

The larger impellers will lower your cruise RPM, which should save you some fuel.
 

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Not sure of all sizes but, I do know there is a AAA. I bought one and want to try it with my 14-71 blown 541" I am building for my '74 Rogers.
The bowl had to be machined to fit the impeller.
Steve
That sounds like a wicked boat. What Rogers hull do you have. Hopefully you've researched the hulls abilities. I think the 18-19 Bonnevilles are capable of 110-115. Not sure how accurate that is though. Would love to see some pics! Sounds like a cool deal so far.
 

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Discussion Starter #20
I'd be curious to see where my combo peaks at and what impeller you guys think I should try. I'm by my build sheet today, and can give some better cam info if need be. Thanks in advance.:)coffee
 
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