SoCal Jet Boats
Tech Talk => Jet Pumps => Topic started by: electrowoman on June 06, 2010, 08:25:59 AM
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I was asked today if a loader could cause engine rpms to be lower? I don't see how
but you guys are the experts so I told him I would post the question.
He changed cams to a supposedly better cam and lost 200 rpms. It's a 460 berkeley 12je A impeller.
The only other thing he did was put on the loader. I vote cam.
Opinions? Tom??
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Yes, it is possible since a loader loads the motor harder than a rock grate.
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Yes, it is possible since a loader loads the motor harder than a rock grate.
x2
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So if that is the case what is the solution? Speed and rpms are down.
Put the rock grate back on and see what happens?
Then change cam back and put the loader back on if the loader isn't the issue?
The up ramp of the loader was trimmed to be at the same point as the bottom of
the original rock grate.
What do you guys think?
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one change at a time, take the loader off and put the grate back on. the new cam may not be rite for the impeller
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Or get a semi-blocker loader or a full v blocker loader (wont load the pump as hard, and possibly adds transom lift) but they *may* cavitate if you take off too hard.
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As said , an aggressive loader (worse if not "adjusted" ) can pull the motor down a bit and this is even more noticable with smaller HP Tom
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Does anyone have a picture of a smi-blocker or v blocker? I only have a rock grate loader, and a ramp loader, and when I swapped them out I had no rpm gains or losses
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Does anyone have a picture of a smi-blocker or v blocker? I only have a rock grate loader, and a ramp loader, and when I swapped them out I had no rpm gains or losses
Heres our Semi pro open,Ill dig up some more pics for ya of my others ! Tom
(https://www.socaljetboats.com/proxy.php?request=http%3A%2F%2Fi147.photobucket.com%2Falbums%2Fr319%2Fjetboatperformance%2FNew%2520Products%252009%2FResizeofP1010155.jpg&hash=82c9463a22e66eecba467f2b61683b478f1affe0)
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I used a V blocker in my low HP skijet circle Daytona. No pixs but it's sim to an open center loader with the center filled with a pice of angle welded in so the edge of the angle points down and the legs are at a 45 to the sides. Works good for getting lift. I had no unloading problems once the pump filled. Off the trailer it took a couple of seconds to fill the pump. My motor was a 454 +030 with a single 750dp Holley, Drake alum. exhaust, roller cam. I don't know if I'd use it on a river cruser or drag racing but for circles it made my daytona a winner.
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Got a call a little bit ago. It WAS the loader. Interesting, now does that mean
trim more off the ramp??
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Electro the Question is where were the leading edges of the ramp blades vs true keel ? does this boat have pressure taps/tap ? to read and tune ? (recommend this ;)) Tom
(https://www.socaljetboats.com/proxy.php?request=http%3A%2F%2Fi147.photobucket.com%2Falbums%2Fr319%2Fjetboatperformance%2F2010%2520misc%2FLoaderTrimmingInstructions3.jpg&hash=8f53be68e24689d54d891403f29c05f60afdcc9c)
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If the keel line were right where the rock grate lines were then it was cut right on the button.
It's hard to tell the real keel line as the bottom of the hull starts to slope toward the jet opening.
He just cut it dead on where the bottom of the rock grate was.
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Electro the Question is where were the leading edges of the ramp blades vs true keel ? does this boat have pressure taps/tap ? to read and tune ? (recommend this ;)) Tom
(https://www.socaljetboats.com/proxy.php?request=http%3A%2F%2Fi147.photobucket.com%2Falbums%2Fr319%2Fjetboatperformance%2F2010%2520misc%2FLoaderTrimmingInstructions3.jpg&hash=8f53be68e24689d54d891403f29c05f60afdcc9c)
Tom, no pressure taps.
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Pressure taps are a valuable "tool" in diagnosing and adding/subtrcting underwater hardware (shoes loaders etc) recommend everbody give thought to them the infomation gives a way to anaylize vs expirimenting thus saving valuable lake trip time Tom
this is the suction Josh is prepping for my boat , the "e" in the pic below is also tapped
(https://www.socaljetboats.com/proxy.php?request=http%3A%2F%2Fi147.photobucket.com%2Falbums%2Fr319%2Fjetboatperformance%2Fmach1%2FDSC08860.jpg&hash=7c434710559a5fc196ffabcfdbe5a76d27f3b076)
(https://www.socaljetboats.com/proxy.php?request=http%3A%2F%2Fi147.photobucket.com%2Falbums%2Fr319%2Fjetboatperformance%2Fjosh%2FGlastron-01.jpg&hash=e829f5c1399f7377032debcbe5e4c56d92012a30)
(https://www.socaljetboats.com/proxy.php?request=http%3A%2F%2Fi147.photobucket.com%2Falbums%2Fr319%2Fjetboatperformance%2Fjosh%2FGlastron-03.jpg&hash=573a6e873bba3df9650dd2de9b7e84838cff43e9)
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What pressure would we be looking for, fore and aft of the impeller? What
pressure range would we be looking at?
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kind of general for a lake boat but we'd like to see you making around 15/30 +- psi on the bottom and 15/30 +-( close to equal at the top maybe a little higher on top ), suction taps located just fwd of the WR and then tune from that point. shoe depth (biting edge) , the depth of the loader horizontal blades below keel line and intake opening size affect more than just intake pressures they also can effect the overall handling of the hull That said while doing this its very important to observe how it the boat feels, drive and handles , Beware and pay attention to how the boat reacts when you "set it down" ,eg "hooking" , "light a$$" end feel , on hard decel from speed, pay special attention to the gauge readings on shutdown as well Tom