Harris Marine Forum - Tech Questions

Any advice

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  1. Mike
    Mike

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    I have started this so that anyone can ask a question about anything to do with jetboats, Weather it be a jet/motor/hull or anything else to do with the boat.
    If I cannot answer it I will find some one that can or others here may have the answer.

    Mike

    Posted 12 years ago    #                  
  2. MOHAWK
    MOHAWK

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    Have you ever done tests on how much planing strakes affect hull performance?

    Posted 12 years ago    #                  
  3. Mike
    Mike

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    Yes, I have been playing around with different size ones on my boat. Larger ones (wider) give much more lift and sit the boat up higher.If they are deeper as well they cause the boat to knife in a hard turn at speed.....While plaining are a pain and need replacing once in a while, It is well worth having them for the lift they provide in shallow water.

    Mike

    Posted 12 years ago    #                  
  4. MOHAWK
    MOHAWK

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    I asume the boat sitting higher would increase speed , have you checked with a gps as to how much? . also how badly do nackerd strakes affect performance?

    I guess by now you realise ive just choped mine off and dont have the abillity to replace them.lol.

    Also could you please explain the different properties of ali used in boat construction and what you would recomend for different areas of the hull.

    Also with regards to my boat stalling when i come off the gas, you sugested an excellerator damper. I fitted one from an efi engine (perfect fit between throttle link and bowl ,will post pic when speckle gets outa bed) and it made a huge differance,, works realy good.

    thanks heaps .Shane.

    Posted 12 years ago    #                  
  5. MOHAWK
    MOHAWK

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    damper pics

    Attachments

    1. 0016_[320x200].JPG (19.6 KB, 5 downloads) 12 years old
    2. 0014_[320x200].JPG (32.1 KB, 7 downloads) 12 years old
    Posted 12 years ago    #                  
  6. Mike
    Mike

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    Yes it helps with speed up to a point. The strakes give you lift as well as directional stability, We notice that the boats get a little more slippery with damaged inner strakes .....but the outer ones hardly ever get a pounding so its minimal,
    In the upper end of performance strakes become more important (you dont see a sprint boat without them!!)

    5083 grade is the full high tensile grade used for the delta. Then there are various marine grades that can be used. There is 5052 (different grades of this as well) that is used in the sides and top deck as well as fuel tanks etc.
    There are different grades so that some can be folded easier than others.
    Good to hear the dampener worked :-)

    Posted 12 years ago    #                  
  7. Timothy
    Timothy

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    Hi Mike, I wanting a option to swap all my gear into a alloy hull of some kind and was wondering your advise.

    I have:
    Fireball (is in V good cond.)
    Holden 253
    Ham 752, 19 degree bullet

    I have been looking around at all different hulls and not too sure what would be good. I mainly go up the waimak, but often take it to smaller rivers and also fishing in lakes etc. So would have to have a bit of room for rods etc but good in shallow water.

    How much money would I need for a full conversion of all of my gear + things like seats and anything else I might need. Am I looking at $10k + ?

    I have looked at tuicraft 460's, rivercraft's and various others.

    Whats good value for money? I don't want to spend to much this/next season.
    Cheers!!!!!

    Posted 12 years ago    #                  
  8. Mike
    Mike

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    At the end of the Day the Best advice I can give is to Go for a ride in as many demonstrator boats that you can and make a decision based on that,,,,dont listen to all the so called experts...decide for yourself after trying them.

    Posted 12 years ago    #                  
  9. Hoihere
    Hoihere

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    I was wondering if you had any advice on how i can grow more grass for my cows ? They seemed a bit hungry today ,any ideas ? :mrgreen: :mrgreen:

    Posted 12 years ago    #                  
  10. Mike
    Mike

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    Simple.....Make lots of steak, That should solve the problem :mrgreen:

    Posted 12 years ago    #                  
  11. midjet
    midjet

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    Mike,
    I was just looking at the picture of your demonstrator boat trailer and noted that it has 4 stud hubs with brakes. Here in Australia I'm having trouble sourcing 4 stud hubs (nissan) for brakes, weather they be hydrolic overide or mechanical overide. What brand are the hubs that you use? I got 4 wheels extra cheap with new tyres off a 92'Nissan Pulsar and i am trying to get some hubs and discs to suit with mechanical overide calipers.

    Cheers Dan

    Posted 12 years ago    #                  
  12. Mike
    Mike

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    Hi Dan thay are made here, Email me if you want a price (same brakes as on matthews trailer)

    Posted 12 years ago    #                  
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    Heathen

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    Giday Mike... I've got a small fault with my boat that I've been putting off sorting.
    It's a Harris Marine lexus/microtech/scott combo.
    About 2 months ago when i start the boat from dead cold it feels like it's running on 7 cylinders instead of 8.(it may not be down on one cylinder, it just feels/sounds like it). WOT is down at only 5000rpm...when cruising along at 2500-3500rpm i can feel the boat surging slightly, like the 8th cylinder firing , then not.
    Once the boat heats up to full operating temp and everything is nice and hot it runs fine . WOT back up to 5400rpm. no surging.
    Any ideas before i buy a new coil and ignitor and change them out one by one.
    I have checked the plugs...all visually fine...
    Do you install all new rotors and caps on your lexus combos??

    Cheers,

    Antony.

    Posted 12 years ago    #                  
  14. Tony737
    Tony737

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    Could be the leads?

    Posted 12 years ago    #                  
  15. Mike
    Mike

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    It sounds like a lead, You should be able to confirm it by running it up to 3000rpm and lock the throttle (while tied to the trailer)and while it is doing it remove each injector plug in turn....this should show up which cylinder is causing the issue..Try this and let me know,

    Posted 12 years ago    #                  
  16. Timothy
    Timothy

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    Hide ho,

    Just bought a Holley 350CFM (ripp off brand) to put on my holden 253.

    Runs fine with 3/4 throttle up to 3500rpm, when WOT it "bogs" down and sounds like shyt and RPMs drops, sometimes giving a backfire (or detonation?)

    The float level seems okay (have tinkered)

    At first I though the jets may have been too small, so I tried 72mm and even 80mm but that made it worse! So now I have some smaller ones (63mm) that I will try tomorrow, but Im not sure this is going to help.

    It could be that its a shyt carb? Could be overfueling ?

    Not sure what else to try. nb. It ran fine on the 253 factory carby.

    Any help ?
    Cheers!!

    Posted 12 years ago    #                  
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    Willow

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    Timothy - 2 hours ago  » 
    Hide ho,
    Just bought a Holley 350CFM (ripp off brand) to put on my holden 253.
    Runs fine with 3/4 throttle up to 3500rpm, when WOT it "bogs" down and sounds like shyt and RPMs drops, sometimes giving a backfire (or detonation?)
    The float level seems okay (have tinkered)
    At first I though the jets may have been too small, so I tried 72mm and even 80mm but that made it worse! So now I have some smaller ones (63mm) that I will try tomorrow, but Im not sure this is going to help.
    It could be that its a shyt carb? Could be overfueling ?
    Not sure what else to try. nb. It ran fine on the 253 factory carby.
    Any help ?
    Cheers!!

    So why did you swap carbs? The factory Rochester Quadrajet seems ideally suited to the 308 we have and probably the same for the 253. Swap back. As to the backfiring, you haven't played around with the ignition timing have you ?

    Posted 12 years ago    #                  
  18. Timothy
    Timothy

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    So why did you swap carbs? The factory Rochester Quadrajet seems ideally suited to the 308 we have and probably the same for the 253. Swap back. As to the backfiring, you haven't played around with the ignition timing have you ?

    I have been told many times that a 350 is a good upgrade for a 253, the original 253 carb was getting old and needed either replacing or re-kitting. No I haven't touched the timing.

    Posted 12 years ago    #                  
  19. mof
    mof

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    Sell the Holley to someone else who has fallen for the Holley marketing machine, and spend the money on getting the Quaddy overhauled. Brilliant carby. Put it down to experience. I got rid of a POS Holley that always backfired when you hit the throttle from cruise. Chzanged jets, change powervalve or whatever, nothing fixed it except an old secondhand Quaddy. Ran like a dream. Had it overhauled, and runs even better.

    Posted 12 years ago    #                  
  20. Timothy
    Timothy

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    Thanks, but my old carb on my 253 wasn't a Rochester Quadrajet. It was a twin barrel Bendix-Stromberg carburetor.
    Just wondering what my problem is, over fueling at high revs is my thought. I seem to have hit a pattern with different jet sizes. The bigger the worse it runs...

    Posted 12 years ago    #                  
  21. vyrusc3
    vyrusc3

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    hi
    could be 1 of many things but
    1..you may have bought a chow piece of shit.......?
    2..where does your vacuum advance line hook up too?if its into the carb itself ,check its getting a true manifold reading,some of the extenal fittings do not do this.put the standard jets back in as they will be fine once you get the real problem sorted.
    theres nothing wrong with a well set up holley,theres plenty of problems to be had if they are set up wrong or randomly modified chasing an unknown problem.
    good luck

    Posted 12 years ago    #                  
  22. vyrusc3
    vyrusc3

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    also...if you had fitted the carb and bounced your way up a riverbed track with no fuel in the bowl,this can be enough to bend the float arm,check the float level with the boat set at the same attitude it planes at also.

    Posted 12 years ago    #                  
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    sheloon

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    if you ask me the carb is too small, my 308 wouldn't rev hard with a holley 470 on it so i went to a 600 and she purrs like a kitten with a hot poker up its a** at rev now, sure the 253 is a smaller engine but same should apply. also my mate had a 253 in a ute and he ran a 600 holley too, much the same response with the kitten also.

    Posted 12 years ago    #                  
  24. Mike
    Mike

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    Yeah, 350 is a bit on the small side......but it could be that the acc pump spring is too strong not squirting enough fuel on hard acceleration. Its a common enough problem with the cheaper hollys......

    Posted 12 years ago    #                  
  25. Timothy
    Timothy

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    Cheers for the advice, I tried a whole different set of jets today, with no change. Runs like crap on WOT. Blows a bit of black smoke too...

    So too small you reckon?

    Holley 600, these are all 4 barrel arn't they? How would I fit onto my manifold? I have an adapter plate that goes from the standard hole to --> the 350 Holley...

    What carbs do you guys recommend, without having to change the manifold?

    also I don't have a electric fuel pump, this won't be a problem will it?

    Posted 12 years ago    #                  
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    sheloon

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    I'd expect black smoke, to me the reasoning is; too small a carby = restricted airflow, which would simulate a rich condition, from the experience i have had with engines when they are too rich they don't rev out, or dont rev up at all sometimes. but, even so, it sould run quite nice in the lower end of the rev range, be torquey and fuel efficient. my 308 is running the mechanical fuel pump and seems to be fine. sorry im not familiar with manifolds and carby compatabilities.

    Posted 12 years ago    #                  
  27. detroitdog
    detroitdog

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    hi, i have been offered an ls1 corvette motor with loom and computer.what would it cost me for manifolds ,heatexchanger etc to retro fit into an alloy hull? also could it be run through a 772hammy untill i get another stage im not after a rocket and is 3500k a good price to pay for an ls1 with just over 100k on it Cheers

    computer and loom are factory

    Posted 11 years ago    #                  
  28. MOHAWK
    MOHAWK

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    Hi Mike, what sort of sealant do you use when installing a unit?

    Posted 11 years ago    #                  
  29. Mike
    Mike

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    detroitdog - 18 hours ago  » 
    hi, i have been offered an ls1 corvette motor with loom and computer.what would it cost me for manifolds ,heatexchanger etc to retro fit into an alloy hull? also could it be run through a 772hammy untill i get another stage im not after a rocket and is 3500k a good price to pay for an ls1 with just over 100k on it Cheers
    computer and loom are factory

    Manifolds are $1650
    one of our heat exchangers is $650+
    Drive block $145
    Modify Loom with all fusing/wiring for dash etc $450
    Computer tune $450.
    You can do it on a two stage with the right impellers but you really need 3 stage.
    $3500 seems about right.

    Mike

    Posted 11 years ago    #                  
  30. Mike
    Mike

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    MOHAWK - 17 hours ago  » 
    Hi Mike, what sort of sealant do you use when installing a unit?

    Use a urethane based sealant, most hard ware places will have it

    Mike

    Posted 11 years ago    #                  

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