SoCal Jet Boats
Tech Talk => Jet Pumps => Topic started by: BFFted on August 25, 2008, 12:57:54 PM
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Hellow I am a first time jet boater and a newbe. I grew up around a v-drive so a jet is new to me. I have a 16ft Tahiti with a stock 390 Ford with a Berkley pump. I can only get 3600 Rpm and 46 mph. Does that sound right? I checked the jet for weeds and rocks. The engine runs good but like I said its stock. I have know idea what impeller it has. I would like to say thanks to Tom a JBP for all the parts and help. I will have pictures soon..Ps.. I am a Ford Guy...
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sorry about the ford thing, you can get over it if you try and really commit yourself to it ;D
welcome to the site and hurry up with pics already :)
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sorry about the ford thing, you can get over it if you try and really commit yourself to it ;D
welcome to the site and hurry up with pics already :)
Thats funny :D
(https://www.socaljetboats.com/proxy.php?request=http%3A%2F%2Fi223.photobucket.com%2Falbums%2Fdd269%2F2savage4you%2Fford.jpg&hash=5231c49d70e171e8825b4d7bea494712e6ae80f2)
Welcome to so cal :sly:
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Welcome bffted do you ever get to flaming george. Your prolly running at altitude. 50 ish for a stock dealio sounds about right to me.
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Colorado here!!!
welcome to the site.
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Welcome to SCJB from someone actually in SoCal ;D
Enjoy the festivities.
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Welcome from So Cal!
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sorry about the ford thing, you can get over it if you try and really commit yourself to it ;D
welcome to the site and hurry up with pics already :)
Thats funny :D
(https://www.socaljetboats.com/proxy.php?request=http%3A%2F%2Fi223.photobucket.com%2Falbums%2Fdd269%2F2savage4you%2Fford.jpg&hash=5231c49d70e171e8825b4d7bea494712e6ae80f2)
Welcome to so cal :sly:
Pay no attention to them BFFted , there just jealous because your boat runs !! ;D
welcome to the fun
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BBF Welcome to the Boards !! Tom
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Welcome to the site.
From Connecticut here.
T.J.
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Hellow I am a first time jet boater and a newbe. I grew up around a v-drive so a jet is new to me. I have a 16ft Tahiti with a stock 390 Ford with a Berkley pump. I can only get 3600 Rpm and 46 mph. Does that sound right? I checked the jet for weeds and rocks. The engine runs good but like I said its stock. I have know idea what impeller it has. I would like to say thanks to Tom a JBP for all the parts and help. I will have pictures soon..Ps.. I am a Ford Guy...
Does anyone know what kind of HP a stock 390 made? I would think that it should be turning more than 3600, even with an AA in it.
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Pay no attention to them BFFted , there just jealous because your boat runs !! ;D
welcome to the fun
my boat runs quite well thank you ;D
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The engine I put in it came out of a 1973 ltd. It ran good and has good comp,oil pressure. I changed the timing chain holley 4 brl intake and put it in the boat. Acording to one of my books it had around 225 hp new. So I have no Idea what it has. It will pull a skier with no problem and is very reliable. I though I should have more RPMS but for a used engine its fine. Thanks for the input guys and I thought I would just get the Ford hazing over with first.( First On Race Day)
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( First On Race Day)
Well would you look at this shit ::) Hey propless you got a brother ? don't tell me there is two of you ;D[quote
author=propless link=topic=4831.msg68078#msg68078 date=1219729492]
Pay no attention to them BFFted , there just jealous because your boat runs !! ;D
[/quote]
Yeah it runs slow.............. BFFted , just messin with ya man :D
(https://www.socaljetboats.com/proxy.php?request=http%3A%2F%2Fi223.photobucket.com%2Falbums%2Fdd269%2F2savage4you%2Fchevylogo.jpg&hash=ff86d38a9da38b6a947026326e1c9a90d52d3c69)
Now thats hot ::) ............................... >:D
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Welcome! Hey! Im a marine tech, and I work on mercs and volvo penta's all day long. They mostly use chevys, thats why I'm running a ford!!!
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For
Outstanding
River
Driving 8) ;D >:D
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F ords
O ften
R equire
D isassembly
;D
What the hell does a Chevy owner know? His crap is still wearing a friggen' bow tie :screwy:
Oroville Redenbacher Crate engines ;)
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BBC, BBF, Olds... If its not a 500ci+ blown Hemi it really doesn't matter :o
What matters is that you get it done, get it on the water and have a good time ;D
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BBC, BBF, Olds... If its not a 500ci+ blown Hemi it really doesn't matter :o
What matters is that you get it done, get it on the water and have a good time ;D
Good point . You did mean a 500ci+ Blown Ford Hemi , right ? >:D
Well would you look at this shit ::) Hey propless you got a brother ? don't tell me there is two of you ;D
Yea baby the brotherhood of the MIGHTY BLUE OVAL !!! The family grows every day ;D
(https://www.socaljetboats.com/proxy.php?request=http%3A%2F%2Fi223.photobucket.com%2Falbums%2Fdd269%2F2savage4you%2Fchevylogo.jpg&hash=ff86d38a9da38b6a947026326e1c9a90d52d3c69)
Now thats hot ::) ............................... >:D
SOMEBODY GET A FIRE EXTINGUISHER !!!! 468Bahner's BOW TIE IS ON FIRE !! And its not even in the boat yet >:D ;D
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Ford Hemi, Chrysler Hemi it doesn't matter.
I wanna stick it in a Chevy II Nova anyway >:D
What better way to piss off everyone than cross breed two things that should never meet!
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Ditch that tiny Ford and get some cubes!!! ;) Easiest way to get speed in a jet boat!!!!
And a Chevy helps too!!!!!!!!!!!!!! O0
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I don't need a chevy I already have an anchor. I spent all my fun money for a while. In a year or two I'll build a mean 390 or 410 for it.
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Welcome to the board. They Chevy guys are just upset that their engines require work to be as a big as a Ford >:D
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Chevys, Fords, Mopars ,Olds There all Good ,its all just nuts and bolts Guys ,anything that runs on fossil fuel Floats my boat!! Tom
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The engine I put in it came out of a 1973 ltd. It ran good and has good comp,oil pressure. I changed the timing chain holley 4 brl intake and put it in the boat. Acording to one of my books it had around 225 hp new. So I have no Idea what it has. It will pull a skier with no problem and is very reliable. I though I should have more RPMS but for a used engine its fine. Thanks for the input guys and I thought I would just get the Ford hazing over with first.( First On Race Day)
Hey there and welcome to the boards...although I'm in NorCal.
And don't be fooled by these guys...
Found
On
River
Dead
:D
Now to get to your issue at hand here. A lot of people have pulled engines out of cars and dropped them into jet boats, only to be disappointed by the performance. That's because most car engines are made to pull a low stall torque converter to 2000 RPMs or so. However, a jet pump is more like a high stall torque converter. We'll use mine as an example. You dump the throttle and the pump "stalls" at 5400 RPMs. In other words, the pump will not allow the engine to spin any higher than 5400 RPM. However...
Each size impeller has a horsepower requirement curve. The ideal setup is to use the impeller with a hp requirement curve that closely matches the engine's HP curve. You would select an impeller that will allow the engine to swing up to its peak RPM, or the RPM where it makes the most horsepower.
Knowing this, you would build the engine so that it peaks out at the RPM you want to be able to spin. Then select the impeller that will allow the engine to spin the pump up to that RPM.
Also, you wanna build the engine so that it can withstand high RPM for long periods of time as well. Mine cruises 3500RPM @ 40mph which is a great speed to cruise at. But there will be the bursts...you just cannot stop the urge to dump it to the floor once you get comfortable with doing that.
Also, it's not ONLY how much horsepower you're making, it also matters what RPM you're making that horsepower at. Also remember that horsepower comes from torque and RPM.
Remember..all the engine is doing is spinning a water pump. The engine and pump have no idea that they're attached to a moving boat. The engine and pump could be mounted stationary and they're still gonna spin the same RPM and do the same thing as they do on a moving boat...pump water. The engine/pump combo does not see a load difference between forward/reverse or slow/fast speeds. The forward motion of the boat has little to no effect on RPM. The RPMs don't increase as the boat gains forward speed like a prop boat or a car would.
The more water it pumps through, the more the load demand goes up. Torque is key here...jets love torque. The more water you push through the pump, the harder the engine will have to spin it to increase its RPM.
Good luck with your venture.
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Hey there and welcome to the boards...although I'm in NorCal.
And don't be fooled by these guys...
Found
On
River
Dead
:D
Now to get to your issue at hand here. A lot of people have pulled engines out of cars and dropped them into jet boats, only to be disappointed by the performance. That's because most car engines are made to pull a low stall torque converter to 2000 RPMs or so. However, a jet pump is more like a high stall torque converter. We'll use mine as an example. You dump the throttle and the pump "stalls" at 5400 RPMs. In other words, the pump will not allow the engine to spin any higher than 5400 RPM. However...
Each size impeller has a horsepower requirement curve. The ideal setup is to use the impeller with a hp requirement curve that closely matches the engine's HP curve. You would select an impeller that will allow the engine to swing up to its peak RPM, or the RPM where it makes the most horsepower.
Knowing this, you would build the engine so that it peaks out at the RPM you want to be able to spin. Then select the impeller that will allow the engine to spin the pump up to that RPM.
Also, you wanna build the engine so that it can withstand high RPM for long periods of time as well. Mine cruises 3500RPM @ 40mph which is a great speed to cruise at. But there will be the bursts...you just cannot stop the urge to dump it to the floor once you get comfortable with doing that.
Also, it's not ONLY how much horsepower you're making, it also matters what RPM you're making that horsepower at. Also remember that horsepower comes from torque and RPM.
Remember..all the engine is doing is spinning a water pump. The engine and pump have no idea that they're attached to a moving boat. The engine and pump could be mounted stationary and they're still gonna spin the same RPM and do the same thing as they do on a moving boat...pump water. The engine/pump combo does not see a load difference between forward/reverse or slow/fast speeds. The forward motion of the boat has little to no effect on RPM. The RPMs don't increase as the boat gains forward speed like a prop boat or a car would.
The more water it pumps through, the more the load demand goes up. Torque is key here...jets love torque. The more water you push through the pump, the harder the engine will have to spin it to increase its RPM.
Good luck with your venture.
Very well put Jetaholic!!! And BFFted, here's one of the impeller charts he was speaking of. Unfortunately, your rpms are too low to use the chart. But, it will give you an idea of what he's talking about.
(https://www.socaljetboats.com/proxy.php?request=http%3A%2F%2Fi201.photobucket.com%2Falbums%2Faa150%2FSleepercp%2Fscan0004.jpg&hash=dbfe237a99888fe1d85ed3556d55d92ece572c71)
But here's one that covers the entire rpm range. According to this chart, with your approximate 225 HP, you should be able to turn an A impeller to about 4000 rpm +/- a few.
(https://www.socaljetboats.com/proxy.php?request=http%3A%2F%2Fwww.hi-techperformance.com%2Fimages%2FImpeller_Chart.jpg&hash=69fa8b78523049f2ddf06ae97493d9ee288a37f9)
Good luck.
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Actually that's the extended chart for engine/pump combos that spin at 6000 and above. Here's the correct one.
The way the impeller sizes work...an A impeller will load the engine more than a B. But it also moves more water per RPM than a B as well, which is why it loads the motor harder. A boat equipped with an engine that can spin an A to 5500RPM will go faster than a boat with an engine that can only spin a B to 5500RPM because more water is being moved by an A at 5500 than a B at 5500. The tradeoff is you have to be able to make enough power at 5500RPM to pull the A to 5500RPM.
(https://www.socaljetboats.com/index.php?action=dlattach;topic=4831.0;attach=18786;image)
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Thanks for all the input guys this site is great!!!
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I love this bar ;D ;D ;D ;D ;D
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Welcome to SCJB from someone actually in SoCal ;D
Enjoy the festivities.
Welcome along, and some good info on this topic.
I work in SoCal, if that helps. :)