Porsche power for a jet boat
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Porsche power for a jet boat

  1. #1
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    Default Porsche power for a jet boat

    Hi all,

    I have been out of boating for quite a few years and during the interim I have taken up Porsche 928s as a hobby. For a brief period, Porsche dabbled in marine versions of their 928 based water-cooled V8s. I have one of these marine conversion kits and want to build a jet boat around it. Im sure I can get much more bang for the buck with American iron but the novelty of running the 928 engine is what this project is all about.

    So now my questions to you, the experts:

    In stock form, I have only 300HP @6500 RPM. Do I have any chance at all of reaching 70 MPH with a jet?

    What type of hull will give me the best performance?

    Anybody have any good candidates for sale? Glasswork and paint are no problem. I would prefer something without an engine but with a good pump setup in place.

    Any and all help or advice is appreciated.

    Thanks
    Dave T

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    Senior Member DuaneHTP's Avatar
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    Yes, It has been done. A friend of mine had one in a larger V-Bottom boat, (actually Too big of a boat). It would work in something like a light TX-19 pretty well. If you cut the impeller to reach the required RPM the motor needs to make its power, you will make the pump too inefficient to be very usable, (top speed only type boat). If you run a larger impeller and put it through a gear reduction box it will be a usable boat. Not fast-usable. Not Economical-usable. This would probably be one of those projects that you could spend thousands of dollars on just to say "I did it," but the out come would most likely be disappointing.
    Duane HTP

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    mo balls than $cents$ IMPATIENT 1's Avatar
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    damn sure would be a neat project

    Dare to be different, if it turns out great you can claim you planned it that way.

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    Quote Originally Posted by DuaneHTP View Post
    Yes, It has been done. A friend of mine had one in a larger V-Bottom boat, (actually Too big of a boat). It would work in something like a light TX-19 pretty well. If you cut the impeller to reach the required RPM the motor needs to make its power, you will make the pump too inefficient to be very usable, (top speed only type boat). If you run a larger impeller and put it through a gear reduction box it will be a usable boat. Not fast-usable. Not Economical-usable. This would probably be one of those projects that you could spend thousands of dollars on just to say "I did it," but the out come would most likely be disappointing.
    Duane HTP
    Helpfull info, thanks.

    At what RPM range are most standard pumps designed to run ?

    I have heard of one Porsche powered effort ( called a Kineo) and it pops up on ebay once in awhile. It's a 27 footer and looks like it's fairly well loaded with heavy "stuff". I can't really believe it can do the claimed 70 MPH. Pictures of it's engine and bell housing look like the exact parts that I have so I am fairly certain my components were for a jet application.

    I'll try a coupl of pics...
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    mo balls than $cents$ IMPATIENT 1's Avatar
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    Quote Originally Posted by Tass 928 View Post
    Helpfull info, thanks.

    At what RPM range are most standard pumps designed to run ?

    I have heard of one Porsche powered effort ( called a Kineo) and it pops up on ebay once in awhile. It's a 27 footer and looks like it's fairly well loaded with heavy "stuff". I can't really believe it can do the claimed 70 MPH. Pictures of it's engine and bell housing look like the exact parts that I have so I am fairly certain my components were for a jet application.

    I'll try a coupl of pics...
    a small motor like that will need to turn a few rpms, so shoot for around 6500-7200rpms wot. jetpumps can be "geared" like a car by the impellor cut, here's you a chart:

    http://www.hi-techperformance.com/im...ller_Chart.jpg

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    I think it would be a canidate for the Aluminum Eagle hulls, lighter hull, with tunnel tech. The ZZ34 equiped boats are running 80 plus.
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    Quote Originally Posted by IMPATIENT 1 View Post
    a small motor like that will need to turn a few rpms, so shoot for around 6500-7200rpms wot. jetpumps can be "geared" like a car by the impellor cut, here's you a chart:

    http://www.hi-techperformance.com/im...ller_Chart.jpg
    Thank you...thats very usefull. I do have the option of boosting my HP to around 400 without to much fuss. It looks like that might be a necessary step if I really want decent speed. I'm running a supercharger on one of my car engines...it's simple and is a bolt on deal.
    This is the set-up with an air/water intercooler in a track car application.


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    Quote Originally Posted by sleekcrafter View Post
    I think it would be a canidate for the Aluminum Eagle hulls, lighter hull, with tunnel tech. The ZZ34 equiped boats are running 80 plus.

    I was hoping to end up with something like the boat below. So far I have been unable to find one on the used market...especially in my budget class (which is, "as little as possible")
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    That looks similar to a Taylor hull, which is out there used for fairly reasonable when you can find them. I would have to say with only 300 or 400 hp in a hull as that you would likely not see the high side of 40 mph however. And if you cut the impellor down to where you can get 6000 rpm out of the motor it would have a hard time getting on plane. I am thinking 80 mph would require about 700 hp.

    Torque is the other issue, as jet impellers like big torque number and most big blocks put out about as much torque as hp and I would think the porsche would make less torque than the 300 hp rating... but if you did go the supercharger route it would surely have to help.

    It would be a one of a kind for sure!
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    i'm back!! 1QuickCP's Avatar
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    Cool motor..always loved 928's...id get a race weight CP tunnel and stick it in there..2 seats, just a fun lake/show deal. probably run pretty good with the blower on it..

    My GT2 is running a touch over 700 whp at 1.45 Bar, evo motor kit.2975 lbs carbon fibre interior

    Last edited by 1QuickCP; 12-30-2009 at 09:32 AM.

  13. #11
    Resident Ford Nut Sleeper CP's Avatar
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    Sub-20' boat a Gullwing of tunnel would be great. Put a set of headers and performance cams, ported intake and injectors on that thing and it will wake it up a bunch. Better than 400 hp at 6,500. Just let it breath and it will run strong.

    S CP

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    fast is the other half.
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    Quote Originally Posted by 1QuickCP View Post
    Cool motor..always loved 928's...id get a race weight CP tunnel and stick it in there..2 seats, just a fun lake/show deal. probably run pretty good with the blower on it..

    My GT2 is running a touch over 700 whp at 1.45 Bar, evo motor kit.2975 lbs carbon fibre interior

    you lookin to adopt a grown son? man you got some badasss toys

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    Quote Originally Posted by Bigblockbill View Post
    That looks similar to a Taylor hull, which is out there used for fairly reasonable when you can find them. I would have to say with only 300 or 400 hp in a hull as that you would likely not see the high side of 40 mph however. And if you cut the impellor down to where you can get 6000 rpm out of the motor it would have a hard time getting on plane. I am thinking 80 mph would require about 700 hp.

    Torque is the other issue, as jet impellers like big torque number and most big blocks put out about as much torque as hp and I would think the porsche would make less torque than the 300 hp rating... but if you did go the supercharger route it would surely have to help.

    It would be a one of a kind for sure!

    Factory numbers have the HP at 300 and the TQ at 263. Not exactly setting the world on fire...hate to think it, but maybe it's better suited to ib/ob use? Looking and sounding great is one thing but I can't live with something that putts around at 50 MPH.

  16. #14
    Cas
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    Cool project for sure!
    I think you might be surprised at what you can get out of that engine in a jet boat. Here's a couple of vid's of a Mazda powered jet-



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