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Discussion Starter #1
I did a quick search but couldn't find anything on horsepower or rpm levels at which you need to upgrade the pump shaft. Is there a way to tell the standard and performance shafts apart visibly or otherwise?
Thanks
 

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Boat Nut
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17-4 are the newer HP shafts, the older HP AQ's were magnetic, the old standard shafts were hard chromed for the bushing. Some where around 500HP is the number, mostly it's how abusive you are to the pump really determines the HP cut off.
 

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I did a quick search but couldn't find anything on horsepower or rpm levels at which you need to upgrade the pump shaft. Is there a way to tell the standard and performance shafts apart visibly or otherwise?
Thanks
Alot depends on what you will do with the boat , and like Chuck indicated ,how much HP , you may be surprized to find a modern high strength shaft is very comparable in price to a stock replacement shaft Tom
 

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Ain't Right Racin
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I bet they will hold 900- 1000 hp as long as it isn't loading and unloading the pump
 

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shaft info

chuck and tom have vast experience on these shafts and both gave good answers, my engineer book list the 304 as a yield strength of 31,200 psi and the 17-4 as 145,000 the elongation of 30% and 5% respectively, obviously the 17-4 is much much stronger, have seen some of the 304 twisted like a barber pole with 350 horse engines , this caused by jumping ways and slamming the impellor,, sledom see the 17-4 shafts damaged, like tom stated depends a lot on how you use the boat and if you are replacing the shaft not much difference in the price, if ever intended using bronze or stainless impellor the 17-4 is no where near as likely to warp.
 

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17-4 is the magnetic material, it is very close to Aquamet's strength but substantially less $$.
 

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Discussion Starter #7
thanks for all the input guys.. I'm building 750- 800 horse blower motor and its going in a lake boat that will occasionally see some rough water so a better shaft will most likely be needed. I took a quick look at the shaft a magnet will not stick, so anything else i should look for to see if it might be an upgraded shaft being that the boat already had a blower motor?
 

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thanks for all the input guys.. I'm building 750- 800 horse blower motor and its going in a lake boat that will occasionally see some rough water so a better shaft will most likely be needed. I took a quick look at the shaft a magnet will not stick, so anything else i should look for to see if it might be an upgraded shaft being that the boat already had a blower motor?
You could have a metalurgist test the shaft. From a practical perspective if it was running for any length of time with the blower motor under load and didn't twist or break its likely not a stock shaft, more likely AQ (being its not magnetic). That isn't a guarantee certainly though. Lots of variables.
 

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chuck and tom have vast experience on these shafts and both gave good answers, my engineer book list the 304 as a yield strength of 31,200 psi and the 17-4 as 145,000 the elongation of 30% and 5% respectively, obviously the 17-4 is much much stronger, have seen some of the 304 twisted like a barber pole with 350 horse engines , this caused by jumping ways and slamming the impellor,, sledom see the 17-4 shafts damaged, like tom stated depends a lot on how you use the boat and if you are replacing the shaft not much difference in the price, if ever intended using bronze or stainless impellor the 17-4 is no where near as likely to warp.
If you do a mild H.T. you up the numbers more. I always recommended 500 H.P. as the base change point, which we also recommended Impeller change to Mag Bronze or S/S also a 7 to 9 pound Impeller increase also. Aggressors 17-4 had a Mild H.T. FYI
As cost on Stainless went up we dropped all but 17-4 which also fit the newer bigger torque motors being produced. Cost became so close little cost advantage to produce the lower. The Aqua Marine shaft has much more carbon and less chromium content thus a lower twist strength. It's name came about as it was a special grind on the entire 12' bar with a much tighter tolerance on streight-ness over a 12' foot length for Prop Shafting, thus the additional cost.
 
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