Anyone have an impeller chart handy? I just rebuilt my pump and motor. I got to run it for the first time today, but I'm at the inlaws lake house 250 miles from home for the rest of the weekend and dont have my books with me.
I,ve got an A american turbine impeller in a dominator pump with pretty tight clearances. Motor was turning 5200rpm on the autometer tack and 5400rpm on the medalion indash tach.
Question is how much HP is the A impeller absorbing at 5200rpm and estimated top speed. My speedo cable kept popping off at 65mph and my dumb butt ran off and left the GPS at home. Boat was accelerating way harder than it did this summer, and before the rebuild the rpm was only 4600 at 62mph.
Thanks
One of the guys came up with a nifty Jet Pump Calculator. I ran your numbers, using 4600rpm at 62mph as the baseline. Using the Dominator pump results were:
523hp@5200rpm at 75 mph.
Using the American Turbine pump:
446hp@5200rpm at 75mph.
I imagine your actual perfomance is right in there somewhere.
Hope this helps.
John
I'd agree with Heatseeker. Assuming your hull doesn't have a nasty hook to buck the trend and that your 4600 before, and 5200 after data points are readings from the same tach, I'd estimate 75 mph (on the same speedo of course). Very nice!
If you'd like to run other points, here's the link to the JPC:
JPC (http://www.angelfire.com/extreme2/dr...erfomance.html)
Which now includes half sizes and Legend pumps.
Speaking of pumps vs impellers, if you have a Frankenstein http://free.***boat.net/ubb/smile.gif, that is a Dominator pump housing with an American Turbine impeller, my guess is your best estimate of hp is to run JPC numbers with the impeller manufacturer instead of the housing manufacturer. For example, 5200 rpm = 446 hp. Tighter than normal clearances will throw your numbers off from the manufacturer's curves...something I can't account for just yet. Let us know what happens on the GPS run!
Cheers,
jer
Thanks for the help. I'm still kicking myself for leaving the GPS at home. It is impossible to measure changes with out good data, but the boat was a blast to drive. With the new pump and motor it startled me and my girlfriend the firstime I nailed the throttle(not to mention what it did to her mom who had never been in a jet before). I wish I had a little more time on the water, but after about 30 minutes the wind got up to 30mh and the 2ft waves were about to swallow my little 19ft pickle.
That reminds of another Question I had. Is it just me or does it seem like the tunnel hull boats run faster when headed INTO the wind? Mine always reads about 2mph faster when headed into the wind as compaired to running with the wind to my back.
Scott, sounds good for the new motor and pump, and to answer your question, yes the tunnel should run faster into the wind, as with a hydro the more air you pack the less drag there is, just as in a vee boat it will run faster on light chop, than on slick water, less adhesion. On my flats I always ran a rough running surface as compared to a slick one, why, bubbles are faster than slick.
Speaking of rough surfaces, I was thinking of sanding my bottom- um, I mean the boats bottom this winter. I have heard to use 320 grit sandpaper to rough it up. My boat is a PlaceCraft tunnel, so should I use the 320 from the tunnels out, and then make it very smooth maybe like 600 or finer right in front of the jet intake. How far in front of the jet should it be sanded smooth? Which way do you sand with the rough paper across or along the bottom? I was also thinking of roughing up my ride plate and tunnel plates.
pcrat, on my flats I hadd the painter open his gun to create an over spray texture, just rough enough to create turbulence in the water passing under the boat, thereby creating a loose effect, since I have retired I have heard of several of the racers using the rough surface, as far as sanding to get the effect I am not familiar with that, I would rather use the speed coat product on the running surface than to try and create the effect with sanding.
a sure way to check my theory is to take 2 pieces of glass and put a drop of h20 on one and put them together, then try to separate them, suction huh, now overspray one with paint and repeat the process.
My boat has some sort of speed coating on the bottom, grafite I guess. It is dark grey color and is slick to the touch, and it will turn your fingers grey when you touch it. It is real smooth though. I've read these smooth "slick" coatings dont really help free up the bottom any, but the "textured" rough bottom like you mentioned will help.
PGF, how did the boat look after you got it sanded and polished?
Scott, it doesn't look like the same boat, it is beautiful, looks like it will be ready to go about the time the weather takes a dump, but this is Texas, just wait a day or so and it will be summer again, I hope.
Can't wait to see it PGF, I will for sure give you a call next time we come through your area. I'm glad it buffed out nice, it is a great looking hull.
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