7.0L EFI or 7.3L PSD for jet drive boat

Discussion in 'Jet Drives' started by aktmboyd, Mar 26, 2014.

  1. aktmboyd
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    aktmboyd Senior Member

    Is it true that a new Hamilton HJ213 retails for almost $18 000. Holy Sh!! If so why.
     
  2. aktmboyd
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    aktmboyd Senior Member

    If I were to have an overdrive for the diesel say at 1:2 overdrive max torque is low at 1800 for international and i think for ford it's 2200. That would be 3600-4400 working rpm on the jet. If something like this was able to be done would this effectively cut your max hp and torque in half or would it be less of a loss. At a 7.3 factory setting of 250hp and something to the tune of 550ftlb torque after the 1:2 overdrive would you have 125hp and 250ftlb torque that sounds pretty week if I am right. Is there any over drive units available for this type of situation. I have a 38 foot downeaster that was given to me it has a big Volvo six in it and a reverser the hull is shot same with the motor, some nut cake pulled the exhaust,intake and some of the injectors out and left the boat for years like this. But the reverser is still there I am wondering if the gearing could be reworked in it to achieve a usable overdrive. Obviously mounting would be a chore but if you had the gear box mounted to the 7.3's standard's bell housing and then shafted to the pump it might work, maybe. What do you think.
     
  3. aktmboyd
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    aktmboyd Senior Member

    Just looked up the power specs for the 03 powerstroke 275 hp at 2800 rpm and 525 ftlb torque at 1600 rpm. Does any one know a torque figure for a healthy 5.7l jet boat.
     
  4. aktmboyd
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    aktmboyd Senior Member

    What is more important for a jet pump. High horse power or high torque?
     
  5. aktmboyd
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    aktmboyd Senior Member

    Baeckmo, this question is for you. Do you remember how the wiring was for the ECU on the 7.3L powerstroke. Thanks for any info on this.
     
  6. Barry
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    Barry Senior Member

    You can ignore torque and only deal with horsepower numbers.

    People often get bogged down with what is better horsepower or torque without understanding the two.

    First
    Torque is a STATIC measurement. Say you have a winch that has a drum that is 2 feet in diameter, one foot in radius and you have a rope on it that has a weight that is 100 pounds hanging off it. You have a handle on the drum that is one foot long. You will statically feel 100 lbs of force and at the 1 foot distance, this will be 100 pounds feet of torque

    Nothing is moving.


    Now you crank the handle enough so the weight moves up 1 foot. You now have done 100 foot pounds of WORK. It does not matter if it takes one minute or one hour.

    But now you crank it fast enough so that the weight moves up 550 feet in one second. You now have a rate of doing work, of 550 pounds feet per second. And this is one horsepower. Horsepower is the rate of doing work.


    The torque number that is given in engine performance curves shows how much sustained torque that the engine can maintain at different revolutions per minute.

    The measurement of this static torque is easy if you hook an engine to a dyno, with electric, hydraulic or strain gauges to measure what the engine can produce as torque but it always with respect to revolutions per minute ( or whatever units you want to use)

    A person would then run the torque into the equation to see what the engine will produce at that specific rpm and calculate the MAXIMUM HORSEPOWER THAT THE ENGINE CAN PRODUCE AT THAT RPM UNDER VARIOUS INLET AND EXHAUST PARAMETERS.

    These horsepower curves show the max that engine can produce under specific conditions which are often very inefficient fuel consumption values. Ie the amount of horsepower produced as compared to the fuel flow rate in.


    If you take two engines, a gas that produces 100 foot pounds of torque at 2000 rpm, it will produce 38 horsepower, if you had another engine that produces 200 foot pounds of torque at 2000 rpm it will produce 76 horsepower.

    This is reason that you have to match the impellor to the horsepower curve that the pump manufacturer specs.


    If you were to have a gas engine producing 400 horsepower at 4000 rpm, it will require a certain impellor. If you had a diesel engine that produces 400 horsepower at 2000 rpm, you would have a different impellor.
     
  7. Barry
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    Barry Senior Member

    So the question then is what is a horsepower figure for a healthy 5.7 litre jet boat

    Most of the 350 5.7 that we used ran were about 310- 320 horsepower MATCHED to Berkleys, Kodiak 3 stage, Hamilton 777 3 stage, and Hamilton 212's and they were healthy.
     
  8. aktmboyd
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    aktmboyd Senior Member

    So with the 7.3L 275 hp's that's a little light for a jet drive. But I think with maybe with a little aftermarket 400hp is totally doable and still in a safe zone for the motor. I have subscribed to a magazine called diesel power for years now and I have seen 7.3L trucks on the Dino at over 800hp and well into the 1200 and 1300 ftlb torque range. I realize this type of power might not be applicable for marine use, but it is a good starting point for what a motor is capable of. My biggest problem still is rpm. I know they can spin the 7.3's well past the 2800 rpm range but I have read the first thing to have problems is the push rods they are week and rpm out of the 7.3 is not what I want, now if it was my 6.0 or maybe a 6.4 twin turbo it would be a different thing, they like to sing for a diesel motor. But still I want to overdrive the motor keep it where it wants to be and match the ratio to a working rpm for a jet.
     
  9. aktmboyd
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    aktmboyd Senior Member

    There are a couple of older Chevy 1 tonne trucks with 5.7's in them here in town that the motor can be liberated from. Of course they will need a rebuild, easy done. But I want to exhaust all possibilities of the 7.3. It is much newer and the truck only has 120 000km on it. It was parked at the dump here not because there is motor issues, but the hamlet could not keep a clutch in it. The locals don't know how to drive that kind of stuff.
     
  10. aktmboyd
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    aktmboyd Senior Member

    All of this is free to the taking that's why I am wanting to go this way. The jet drive is going to be the biggest expense for the whole project.
     
  11. aktmboyd
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    aktmboyd Senior Member

    Barry thanks for all your input so far, keep it coming
     
  12. aktmboyd
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    aktmboyd Senior Member

    Also I still have not dropped the idea of going in/ob, but I would rather the jet for, simple piece of mind.
     
  13. Barry
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    Barry Senior Member

    To your question, is 275 hp enough? (For the diesel)

    Now is the time to look at the horsepower curve requirement for say a Hamilton 212.
    (212s are not 18,000)
    They will have an impellor to match this horsepower BUT FOR THAT RPM. 275 is a lot of horsepower.

    Remember I said that the horsepower curve that manufacturers often put out are for the MAXIMUM that the engine can produce, not what is efficient or what the engine is putting out for a given rpm. Say and engine can produce 275 horsepower at 3000 rpm at max, that is what the curve shows, but you are parked. You step on the throttle and run the rpm up to 3000 rpm, the engine is not producing 275 hp. It will produce enough to over come the engine friction and inertia horsepower requirements.

    The only time a marine engine will see maximum horsepower is when the throttles are full on and the rpm cannot increase anymore. ( the engine will see closer to max on acceleration)

    At 3000 rpm, 30 mph, our engine used 8 gallons of fuel per hour. We used a Flowscan fuel meter for measurement. I was told by Berkley pump that for every hundred horsepower that the engine is producing, you need 8 gallons per hour for a fuel rate. This was for carbed engines at the time. So to go 30 mph, the engine was producing about 100 hp.

    I see Kem Equipment Kodiak Marine still has their 3 stage pump for sale, not sure on the cost. They were a lower cost pump than the older Hamilton 777 three stage.


    In any case, no matter what pump you use, the impellor has to be matched to the horsepower of the engine AND the rpm that you will run the engine at.

    I would email Hamilton and ask their advice

    If you are planning to troll with the boat, the diesel smell will be bad as the exhaust is on the transom into atmosphere and a wind from the stern will dump this exhaust smell into your boat.
     
  14. aktmboyd
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    aktmboyd Senior Member

    No trolling will be done with the boat. Wrong area for that style of fishing. It's main use is a hunting boat/pleasure boat. I know that a turbo'ed Diesel engine likes to be loaded, to make it's full projected hp. I am still waiting for the manufacturer to get back to me with some more detailed spec on the boat. So do you think and I am not holding you too this or anything but a diesel motor like mine would possibly be able to match a 212 with a big impeller to keep the motor loaded and also be somewhere near the projected tip speed that Baeckmo suggested I believe that was 35-45m/s I need to due some math:?:
     

  15. Barry
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    Barry Senior Member

    I just read the Hamilton brochure on line for the 212 and saw that they do not recommend the 212 diesels except for a few selected higher rpm diesels. Instead they suggest a 213

    If you decide to pay 18,000 for a 213, it might be cheaper to buy a new 212 and a new marinized 5.7 litre

    If you are considering paying 18,000 for a 213, if you factor in all the extra expense that you will have to install your 7.3 into this boat, say another 5,000, it might be better to buy a used ready made jet boat, all done up and ready to go.

    Also I am pretty sure that the 7.3 will have a return fuel line to the fuel tanks so the fuel tanks will need some work. I think new 5.7 have this return line in the AUTOMOTIVE variety as well. A marinized engine omits this return line. And of course the marinized engine will have all the components for marine use already installed
     
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