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MintercreekWa
05-29-2001, 06:16 PM
I am in need of some experienced help here.
I installed a used 500hp 454 in my 1985 18' Advantage Jet Boat. It is a Gen V block. Cam specs are unknown, yet idles around 1100 rpm. Carb is a 800cfm dual feed. Ignition is stock dual point Mallory system (hard to start). Installed a Carter 90gph electric fuel pump (pressure gauge reads 6 1/2 pounds pressure). Berkley pump with "A" impeller.
Took it out in 90 degree weather (Moses Lake, Wa.) and appears to be wanting more fuel and probably a better Ignition System.
Currently ran at 6200rpm, unknown speed (feels about 70 or so). Old 330hp Hardin Marine motor (12 year old ) ran @68mph with 2 on board (per GPS).
Questions:
What Impeller size to go to?
Ignition system?
What is the ideal fuel pressure? 6 1/2pds seems low.
Thank you for all help you can offer.
Update: The pump was blueprinted by Marlin Marine in Renton, Wa. several years ago. I did not notice any slipage with old motor.
Plan on going out this weekend if the rain will hold off and get better readings with a GPS. Guess I will try Long Lake in Port Orchard area, hope there is not a speed limit there.
Have a Manual Diverter with a Roost Booster. These things Rock! Stock Nozzel and Grate.
We goto Moses Lake for the Holiday weekends and camp out in the Dunes. I also got a vintage '86 ATC 250R that is Bored, Stroked, and stretched. I like to smoke modded Banshee's. I hang out with a group (about 13), of Jetter's from Tacoma area that have some beautifull and well cared for boats that run from mid 60's up to about 100mph. We goto Ice Harbor at least once a year, and Banks/Cresant Bar once a year. There is another group of jetter's in Portland area that some of the group Jet with in Sept.
[This message has been edited by MintercreekWa (edited May 29, 2001).]
[This message has been edited by MintercreekWa (edited May 31, 2001).]

HBjet
05-29-2001, 09:19 PM
MintercreekWA, I'm not much of a motor guy, but I do know you should either convert your dual points ignition or get a new one. I had mine converted and it wasn't that expensive. Your fuel pressure seems to be right on, but anyone please correct me if you think different. What you didn't really get into is your pump. Is it bone stock? Has it ever been blue printed? Place diverter? Anyway, with running an A impeller your 6200RPM seems high for 70 or so MPH. My pump is a berk JC which as a B impeller and the pump has also been blue printed by Jack at MPD. I'm pushing about the same HP at 75mph and I'm at 5200rpm. Before I had my pump done, my RPM was about 5700-5800 and the boat was slower. Jack told me that my MPH should increase some and my RPM should drop by 500. The reason for the RPM drop is that the pump is running more efficient. I would look into making sure your pump is tight, and converting that dual point ignition. To me your idle is right on, but you can always play with it until your happy. 1000-1100rpm is where you should be though. My boat idles just under 1100rpm in the water.
Good Luck!
HBjet

HBjet
05-29-2001, 09:19 PM
MintercreekWA, I'm not much of a motor guy, but I do know you should either convert your dual points ignition or get a new one. I had mine converted and it wasn't that expensive. Your fuel pressure seems to be right on, but anyone please correct me if you think different. What you didn't really get into is your pump. Is it bone stock? Has it ever been blue printed? Place diverter? Anyway, with running an A impeller your 6200RPM seems high for 70 or so MPH. My pump is a berk JC which as a B impeller and the pump has also been blue printed by Jack at MPD. I'm pushing about the same HP at 75mph and I'm at 5200rpm. Before I had my pump done, my RPM was about 5700-5800 and the boat was slower. Jack told me that my MPH should increase some and my RPM should drop by 500. The reason for the RPM drop is that the pump is running more efficient. I would look into making sure your pump is tight, and converting that dual point ignition. To me your idle is right on, but you can always play with it until your happy. 1000-1100rpm is where you should be though. My boat idles just under 1100rpm in the water.
Good Luck!
HBjet

MellowYelloW
05-29-2001, 09:20 PM
hey mint, "A" impeller is good. also go with the MSD ignition. not sure about the fuel pres. should run 75-80 though.

HBjet
05-29-2001, 09:21 PM
Sorry for the double post
HBjet
Mellow, are you going to the river on 6/8-6/10? I'll be at Echo. Also, what speed do you get out of your boat?
Thanks
HBjet
[This message has been edited by HBjet (edited May 29, 2001).]

JOESHOW
05-31-2001, 01:52 PM
Mintercreek, I have a similiar engine (mark IV, 475 hp) that I am breaking in right now. I have found that mine also likes to idle at 1000-1100 rpm. I have been told by several people that this is a good spot for a jet boat to idle at. I have adjusted mine down a little bit (800 prm) but I like it better at around 1000-1100. I don't know if more pressure is what you need, but a fuel pump setup with an external (adjustable)regulator would allow you to find out and still be able to adjust it back down without switching back to the old fuel pump.
Also I switched my points distibuter out for a Davis HEI because I wanted more spark and better reliability. I haven't had it long enough to tell if I like it or not but I'll let you know how it works out.
Do you ever go to Moses Lake alot? I am from Yakima and would like to hook up with another Jet boater at the lake. I boat with a good group of guys but will be he only person with a jet. We will being going mostly to Moses and Potholes. Thanks -Shane

mister460
05-31-2001, 03:00 PM
Convert to electronic ignition quick! Fuel pressure is right on though. Should be about 6.5lbs at idle and not less than 2.5lbs at WOT.

froggystyle
06-05-2001, 10:31 PM
2.5 lbs at WOT would scare the #@$! out of me. The Holley seems like it is designed to run with around 7 to 9lbs of pressure at all times. A good electric pump with a regulator will give you very reliable fuel pressure, and usually improve performance as a result. I'm not a builder, but my builder had me look at my pressure at WOT to troubleshoot a high RPM backfire issue, and explained that I should never come off of 7.5 lbs. Different application I'm sure, but the theory would seem to follow on any Holley.

froggystyle
06-05-2001, 10:34 PM
By the way, sounds like a loose pump. Pumps don't feel loose when they are, they just loose efficiency. From what I understand, a well set up JC or JG is damn near as accurate as a dyno as to what horsepower you are putting out the shaft. Meaning that having X impeller at Y rpm = Z horsepower. The variable then becomes hull design. Does anyone know the actual formula, or is this an old-wives tale?

Joker
06-06-2001, 09:14 AM
cpperformance.com has a impellor pump curve with RPM vs. Horsepower depending on impellor selection. All you need to know is RPM and impellor type and the curve will tell you shaft horsepower.......

mister460
06-06-2001, 03:32 PM
Just remember that at WOT the pressure will drop but flow will increase. I should have added in there that a pump making 2.5lbs at WOT also needs to provide a lot of fuel flow as well. It's rare that you see a pump that low during WOT but 2.5 is the low limit. Just like the 10lbs of oil pressure per every 1000 rpm. Sounds low but it will be safe. And that backfire you experienced could have been caused by too much fuel pressure. But I digress, electric pumps are the way to go!

ponponracing
06-06-2001, 06:57 PM
The fuel pressure should be set at a constant 7 pounds. If it drops below 6 pds at wide open trottle, you're missing gas and hp. A holley GP110 will give you 110 gallons of gas per hour, free flowing. A good mechanical fuel pump will give you 135 gallons of fuel per hour, free flowing also.
If you want a real heavy duty electrical or mechanical pump, you have to use a regulator connected to a return line to the tank, exactly like the regular modern electronic injection in your car. You have to make sure the pump you will use is made for continuous operation.
With a Holley carb, if your fuel pressure is set at more than 8-9 pds, there are chances that you will see fuel leaking through the needle&seat assembly, since the rubber o-ring is not strong enough to hold that fuel pressure. In such a case, the fuel level inside carb bowls will rise and fuel will start dropping from the venturies boosters, creating an overrich situation at idle and in the worst case causing a backfire that will bring a carburator fire. Hope you have a good flame arrestor.

SeaSlut
06-08-2001, 08:37 PM
I looked for the power curve calculator at CP, but could not find it.
Where is it?
thanx

Joker
06-09-2001, 05:28 AM
Go to cpperformance.com click on "online catalog" click on "jetdrive" and then find "dynomometer theory" that will bring up the curve.