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Thread: Need some help with a new jetboat.

  1. #1
    Member hntr's Avatar
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    Default Need some help with a new jetboat.

    I think I have the wrong pitched impeller in my new jetboat. I'm not getting the performance that I expected.

    I have a 24 ft Weldcraft with the 454 and a 2.4 TBO impellar. I'm only running about 24 mph at 3600 rpm, takes 4300 to get up to 29 mph. I'm thinking I need something more aggressive.

    Any one have any insight? Idealy I'd like to see if someone has a 3.4 that I could try out without having to buy one.

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    Member Dupont Spinner's Avatar
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    Quote Originally Posted by hntr View Post
    I think I have the wrong pitched impeller in my new jetboat. I'm not getting the performance that I expected.

    I have a 24 ft Weldcraft with the 454 and a 2.4 TBO impellar. I'm only running about 24 mph at 3600 rpm, takes 4300 to get up to 29 mph. I'm thinking I need something more aggressive.

    Any one have any insight? Idealy I'd like to see if someone has a 3.4 that I could try out without having to buy one.
    Hami 212 jet unit? What is your WOT rpm? Top speed on a lake? Need to make sure your tach is correct.

    2.4 seems a little small....I may be able to work you a deal to try my 3.4 but I am thinking you may actually want a 3.0 or 3.2 if running the motor stock and plan on heavier loads. My motor is beyond stock and rarely do I run heavy.

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    Member hntr's Avatar
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    impeller.jpg

    Yes its a Hamilton, sorry, forgot to mention that. The tach does bounce every now and then.

    Those speeds were in PWS haven't had it on a lake yet. The motor and jet is as is from factory previous owner never even had the jet apart. I just took it apart and filed down the leading edge of the impeller, I included what it looked like.

    I do plan on heavy loads of moose meat, but don't we all.

    What is a "WOT rpm"?

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    Quote Originally Posted by hntr View Post
    impeller.jpg

    Yes its a Hamilton, sorry, forgot to mention that. The tach does bounce every now and then.

    Those speeds were in PWS haven't had it on a lake yet. The motor and jet is as is from factory previous owner never even had the jet apart. I just took it apart and filed down the leading edge of the impeller, I included what it looked like.

    I do plan on heavy loads of moose meat, but don't we all.

    What is a "WOT rpm"?
    hntr, Your impeller is in serious need of a rebuild. Filling the edges will do more harm then good at this point. Take it to AK Frontier Fabrication and talk to Garret at the new location behind Six Robblees in Wasilla on Sun Mtn View Ave. He'll be able to rebuild the impeller to better then new condition. Depending on the HP rating of your 454 you may need a 3.4 or 4.0 impeller. You could also try pitching the the 2.4 up to a 2.8 before spending money on a whole new impeller. Depending on the overall weight of the boat, you should be seeing 30mph even with a 2.4 if it's in good condition at 3600.

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    Member Music Man's Avatar
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    Or A-1 impellers in Anchorage
    A-1 Propeller & Impeller





    (907) 344-7767
    1220 E 68TH Ave Ste 103
    Anchorage, AK 99518
    When seconds count, the cops are just minutes away.
    '08 24' HCM Granite HD "River Dog"

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    Yes sir, that impeller looks hammered. Don't forget new wear rings to go along with the impellers.

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    Member Dupont Spinner's Avatar
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    Quote Originally Posted by hntr View Post
    impeller.jpg

    What is a "WOT rpm"?
    WOT = wide open throttle. A 4.0t should only be used with a well prepped 502 or better. I know as I tried but my modded 454 wasn't enough.

    Here is the info right from Hamilton on the 212 and engines.....

    Do you make more than one Turbo?
    There are three different ones: The 2.4T is for the small block Chevrolet 350 and the Ford 351. The 3.4T was designed for Chevrolet 454 & 6.2L as well as the Ford 460. The 4T is intended for the Chevrolet 8.1 and SC 6.2L, but may also be used on some “built” Chevrolet 502. Chevrolet 6L may use the 2.4 or the 3.4.

    What kind of full throttle rpm should I expect to get with the 212 turbo?
    This will vary with the marinization and vintage of the engine, but in general, at or near sea level, we will see something close to the following rpm’s from these common engines:

    Ford 351/Chevrolet 3502.4T 4,100 - 4,200 rpm
    Chevrolet 383 “Stroker” 3.4 4,000 rpm
    Chevrolet 6L2.44,450 - 4,500 rpm
    Chevrolet 6L 3.4 3,900 - 4,100 rpm
    Ford 460/Chevrolet 454 3.4T 4,000 – 4,100 rpm
    Chevrolet 502 3.4T4,200 – 4,300 rpm
    Chevrolet 502 4 T 3,850 rpm
    Chevrolet 8.1 375 hp4 T4,020 rpm
    Chevrolet 6.2L 3.44500 rpm
    Chevrolet 6.2L 3.4T 4200 rpm
    Chevrolet 6.2L Supercharged4T 4250 - 4400rpm

    Most of the boats we see achieve an acceptable cruising speed at 2,800 to 3,300 rpm. However, this will vary widely with the individual boat and load.
    If you’re operating at higher altitude, expect to see a significant drop in rpm’s and power. You will loose roughly 3% of your horsepower for every 1,000 feet in altitude. If you’re in that situation, you may need to use a smaller impeller than you would at sea level to achieve a reasonable rpm. Be aware when running at altitude that standard gasoline engines will lose power, simply changing the impeller will only change the rpm of the jet and engine. Generally it will not make the boat go faster. If speed is required at higher altitudes consider a larger engine or even better a Turbo charged diesel or Supercharged gasoline engine.

  8. #8
    Member Rob B's Avatar
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    Take it to Gary at Greatland Welding in Palmer. Best place around. I agree with the others. It's looking really bad. Get it rebuilt, replace the wear ring and it will seem like a different boat.

  9. #9

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    That impeller looks like a stone mason has been using it to cut bricks in half !!!!!!!

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    Quote Originally Posted by Big Bend View Post
    That impeller looks like a stone mason has been using it to cut bricks in half !!!!!!!
    The guy told me he never sucked up any rocks with it and it never even touched gravel. That's what I get for trusting people.

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    Quote Originally Posted by hntr View Post
    The guy told me he never sucked up any rocks with it and it never even touched gravel. That's what I get for trusting people.
    I told you I sucked rocks with mine and it didn't look that bad....hope your test goes well. Enjoy that thing and thanks for cleaning mine up for me. Sorry it took so long to rip it down. I guess I should take it apart more often. Have a great time, see you when I get back.

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    Alright you guys want to see a hammered impeller and their is a claim that the boat is was able to get on step then follow this link to this forum. I knew I had seen a set that was hammered just didn't know where, but found it for you. Look close at the jig to realize how much material is missing.

    http://www.nzjetboating.com/yabbse/i...?topic=17565.0

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    hntr
    figured out why my impeller was so hard to remove, seems I have a burr on the shaft, will have to clean up before the reinstall. I am now going to make it at least an annual requirement to pull my jet apart. I hate having to heat and beat to get things apart. Hope that thing is now flying for you.

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    Member hntr's Avatar
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    Just got back, took it to the lake to try it out. Wide open it turned at 4100 rpm and got 39 to 40. Cruise at 3700 got 30 mph and 3400 got 25 mph. It definitely got out of the hole much faster. Can't thank you enough for volunteering to help a new guy. And to tear down your jet and pull your impeller to do so. A real class act!

    And I couldn't even get that impeller on until I sanded some burs down on the inside.

    Thanks again

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    Member Grayling Slayer's Avatar
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    I also use plenty of anti-seize when putting it all back together.
    "I'd rather be fishing!"

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    Quote Originally Posted by hntr View Post
    Just got back, took it to the lake to try it out. Wide open it turned at 4100 rpm and got 39 to 40. Cruise at 3700 got 30 mph and 3400 got 25 mph. It definitely got out of the hole much faster. Can't thank you enough for volunteering to help a new guy. And to tear down your jet and pull your impeller to do so. A real class act!

    And I couldn't even get that impeller on until I sanded some burs down on the inside.

    Thanks again
    Probably all the sand rock that has been thru that thing over the last 3 years.

    Well your rpms are about correct. I thought you might see a little higher speed, with cruise at 3k and 30 mph. Going to a 4.0t will drag that thing down pretty far, like maybe 3800 so that's out. Having a 3.4 turndown to a 3.2 might be the trick, I think a 3.0 would be a little to small. The 3.2 should put it about 4300 to 4400, which I feel is the best for a 454.

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    Hey I forgot to ask to you turn your bucket over or leave the way it was????

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    It's pointed down and I left it that way. Wouldn't less pitch like a 3.2 require higher rpms to cruise than what the 3.4 is doing?

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    Quote Originally Posted by hntr View Post
    It's pointed down and I left it that way. Wouldn't less pitch like a 3.2 require higher rpms to cruise than what the 3.4 is doing?
    Yes but.....think of your engine as working to climb a hill, all the time with a boat engine. You could lug it up the hill or you could drop out of overdrive and let the engine ease itself up the hill, also needing to back out of the throttle a little to hold that gear. You know your engine will run the 3.4T but by backing it down to a 3.2 you will gain 200 to 300 rpm at WOT, overall topspeed will be slightly less, cruise speed will be a little lower, but you will not work your engine so hard. That is why I went from the 4.0 back to the 3.4. I was not pushing the engine as hard. I believe my boat really needs a 3.6 or maybe a 3.8 but I want my rpms to be right about 4500. Right now I am right at 5000 rpm on the lake and on an occasion or two I can bump the rev limiter. I am thinking Scott nozzle real seriously right now. I was seriously thinking about driving up to bother Jeff.


    When I get back we will put mine back together and go for a ride and see what you think. You will hear the difference in the work my engine is doing.

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