new build 77 tahiti w/ built 460.. jet pump problem?
+ Reply to Thread
Results 1 to 13 of 13

Thread:
new build 77 tahiti w/ built 460.. jet pump problem?

  1. #1
    Junior Member
    Join Date
    Oct 2014
    Posts
    8

    Default new build 77 tahiti w/ built 460.. jet pump problem?

    heres the scoop, first off this is my first jet boat, been into skis and regular outdrive boats. familiar with engine and mechanics etc. I picked up a 77 tahiti mini cruiser 19' over the winter, tore it completely down and spent all winter building her from scratch. set it up with a 460 ford making aprox 600hp. took her out for the first time and got her running clean and smooth. it has a jacuzzi wj/b with place diverter, was told the boat ran good when it was last in the water in 01 when the guy loaded a ton of nitrous and blew it up and just let it sit. took her out for second time today and it was running perfectly except I'm turning 5k rpm at 45mph gps. from the research i have been doing this doesn't seem right for a motor making around 600hp. motor is fresh rebuild, stock crank/stroke, keith black pistons, eagle rods, scorpion roller rockers, comp cam kit (matched for b impeller), cobra jet heads ported, all new head components, high volume oil pump, crane fireball box, malory dis, 850 holley with cut choke and 80's currently, everything port matched, etc. good solid build with aprox number from machinist. I'm very disappointed needles to say, i was expecting somewhere around 60mph. I'm thinking the weak spot may lie in the pump or there is a different impeller in the boat then the pump tag says. I'm familiar with the slip feeling or caviation on a jetski, but maybe its different in this circumstance? the boat gets up and goes if you hammer it from a dig (doesnt feel like seaweed) but it takes a while, doesn't quite pull hard or jump but also doesn't sound like its caviating. if I'm up on plane with trim about neutral the boat has quick response if letting off and re-applying throttle quickly. from about 4k to 5k it doesn't seem like i gain much mph for a 1k rpm change. before i put the engine in i did a quick check over and the pump was free and smooth with really no play, so i figured there was no major issue. couldn't really get a good look at wear ring due to i was only looking through the access hole in the top and saw the impeller had a outer ring on the blades (different from jetski). looking for an opinion of what you guys think. problem with driveline, or do i have an expensive paper weight of an engine?




    thanks a lot!
    brian

  2. Remove Advertisements
    PerformanceBoats.com
    Advertisements
     

  3. #2
    Senior Member BGMAN's Avatar
    Join Date
    Jan 2008
    Posts
    568

    Default

    600hp on paper can be different than 600hp in real life. I don't recall you actually saying if you dyno'd the motor or not. Regardless of that point, even if you had 350hp, you should be going faster than 45mph. My guess is that it's time the pump be freshened up. Depending on what your plans are with the boat. I would look into an energizer kit for the WJ if you are going to keep the boat for a long time.The energizer kit converts the pump to use more common (affordable) internal parts. The energizer kit will pay for itself in the first 2-3 rebuilds.

    New Jacuzzi parts are expensive, so if it needs a new impeller, I'd look at the energizer kit right off the bat.

    Feel free to PM me for more details, I can get my hands on a kit for you.

  4. #3
    Junior Member
    Join Date
    Oct 2014
    Posts
    8

    Default

    Everything is hp numbers and estimated calculations using pc software, usually decently accurate. Would have loved to dyno, maybe next year. But I agree with what you said a stock boat from what I'm reading does about 45. Other thing is I have not yet buffed it out or really cleaned so the bottom of the hull is a little rough, but I still don't think that I would see that much mph loss from that. Or would I?

  5. Remove Advertisements
    PerformanceBoats.com
    Advertisements
     

  6. #4
    Senior Member BGMAN's Avatar
    Join Date
    Jan 2008
    Posts
    568

    Default

    Depends on your definition of rough. Race boats/ fast river racer boats and see up to 10 mph increases with a nicely blueprinted bottom. If your meaning that the paint/gel is a little rough to the touch then no, that's not where your speed loss is. With the information you have provided, I'm 90% sure your issue in a inefficient jet drive.

  7. #5
    Seriously off center slowride's Avatar
    Join Date
    Dec 2007
    Location
    Anaheim/BHC- the Shack
    Posts
    2,439

    Default

    OT headers or TT log exhaust? Guarantee you're not making 600 with logs. My stock 460 in a 21 open bow with Jacuzzi A is spinning 4300 rpm and 52 mph. Absolutely nothing for me to brag about (and new engine and pump going in this winter), but a comparison for you. My new pump is an Energized WJ with a magbronze AA and inducer. If/when you actually have 600 horse available you WILL need pump work.






  8. #6
    Senior Member Mash on It's Avatar
    Join Date
    Mar 2008
    Location
    Willow Beach & BHC
    Posts
    170

    Default

    Sounds like your wear ring is shot.
    WJ's plastic wear ring will wear out in 3 to 5 minutes, running it out of the water. (Don't ask me how I know)
    Mild 454, cam and headers, turned a WJ 'B' impeller to 51-5200 rpm, at 71.8 in Laughlin/BHC, heavy azz 19' Glenco.

    WJ 'B' @ 5K is in the mid 400 hp range, on a tight pump.

    Dan'l
    "Never mind the mule, Just load the wagon"
    '76 Eliminator 21'

  9. #7
    Junior Member
    Join Date
    Oct 2014
    Posts
    8

    Default

    well, the bottom is just a little rough to the touch, no major imperfections and such. will get a good compound and waxing soon. as for exhaust I'm running OT bassets w/ water injection at 1700rpm using an electronic solenoid and rpm window switch, so it can be changed at any time. long story short i pulled the pump bowl off and got the impeller out. wear ring is SHOT. probably about 1/4" gap between the two and heavy wear shown. impeller is also shot.. to my surprise it looks great from the access hole inside the boat, from the bowl end there are chips in every blade and some bends. I'm very surprised the boat actually reacted as well as it did with the pump in the condition its in. bushing and bearings are great. the shaft has no play back and forth with the impeller and bowl off. i think i will be in good shape just replacing impeller and wear ring and re-sealing it nice and tight. does anyone know where i may be able to source a used good shape b cut impeller? not really looking forward to spending 500+ dollars on a new one, i plan to rock a tight jacuzzi for a season and do an energizer kit next year.

  10. #8
    Senior Member jetboatperformance's Avatar
    Join Date
    Dec 2007
    Location
    Atascadero Calif
    Posts
    7,463

    Default

    Quote Originally Posted by Wakeboardcraze View Post
    well, the bottom is just a little rough to the touch, no major imperfections and such. will get a good compound and waxing soon. as for exhaust I'm running OT bassets w/ water injection at 1700rpm using an electronic solenoid and rpm window switch, so it can be changed at any time. long story short i pulled the pump bowl off and got the impeller out. wear ring is SHOT. probably about 1/4" gap between the two and heavy wear shown. impeller is also shot.. to my surprise it looks great from the access hole inside the boat, from the bowl end there are chips in every blade and some bends. I'm very surprised the boat actually reacted as well as it did with the pump in the condition its in. bushing and bearings are great. the shaft has no play back and forth with the impeller and bowl off. i think i will be in good shape just replacing impeller and wear ring and re-sealing it nice and tight. does anyone know where i may be able to source a used good shape b cut impeller? not really looking forward to spending 500+ dollars on a new one, i plan to rock a tight jacuzzi for a season and do an energizer kit next year.

    The WJ when "tight" and working right is a very good performing jet unfortunately although Jacuzzi (NAMJ) still supports their small jet drive market and OEM parts for WJ's and YJ's and most parts are still available and stocked , they (Jacuzzi parts) are produced in smaller quantities then in yesteryear and thus can be a bit spendy ,there lots of good used "spares" and very after market parts are still available as well as mixed flow conversion kits which really make these pumps work well Call if we can help with options and tech help Tom 805 466 4719 anytime

  11. #9
    Seriously off center slowride's Avatar
    Join Date
    Dec 2007
    Location
    Anaheim/BHC- the Shack
    Posts
    2,439

    Default

    Hate to hijack, but Tom.... your inbox is full.






  12. #10
    Senior Member andyc's Avatar
    Join Date
    Feb 2010
    Location
    Valley of the Winds
    Posts
    302

    Default a thought ??

    I have also see worn out nozzle rings too.Thrust loss for sure. Look over the back while someone is driving and observe if water is completely directed out of the nozzle and not ALSO coming out from the housing. In your case it would be where the diverter connects to the pump-the Left/Right swivel end. If that is the case, replace with a PlaceDiverter O-ring which is fatter. I believe a worn out pump too, but still something to cover as well. Just my 2cents.

  13. #11
    Junior Member
    Join Date
    Oct 2014
    Posts
    8

    Default

    thanks. good piece of advice there. i plan on replacing every r-ring while I'm here. currently waiting to find another impeller or get mine repaired. also have to fill weld some chips in the bowl and do some grinding, unfortunately i am not skilled enough to know how to correctly repair and pitch the impeller.

  14. #12
    Junior Member
    Join Date
    Oct 2014
    Posts
    8

    Default

    quick update and possibly bring back a little bit of an old thread. its cold here in NJ but i had a warm day last weekend and got her back together with a welded bowl to fix the rock chips on the blades, and new B impeller with new wear ring and o-rings. turning about 5500rpm and getting 55 trim up-60mph fine tuning trim.. does that sound right?? bottom of boat is still pretty rough (sand and buff to come this winter) and i was running stock intake. also i would like to add i have the old style place diverter where it is not actually the nozzle. it is the non o-ringed version.

  15. #13
    Senior Member
    Join Date
    Mar 2009
    Posts
    3,363

    Default

    Not trying to hi-jack, but my CVX-20 jet has a bottom that is scratched up- Side-to-side....In the delta, they install rock dams to hold the water higher in certain areas during the "dry" summer months, and at some of the dams, they have a guy there with a "Universal" trailer who moves you past the dam....>I< did it once, and noticed that the bunks were...not well covered, as we swung around to back down the boat "settled"....I could tell when I got home that there were more scratches...Never did it again, but the previous owner lived in the area where there were a bunch of those dams, so I suspect thats where the scratches came from....

    Anyway, I have always noticed that the boat will get up to 30mph @ 2800 rpm when first pulling out of the marina- but after a few turns and stop & goes, the boat needs 3000 to get to 30....I suspect that those scratches are holding some air, which kinda "lubricates" the hull until the air gets washed out....I don't have proof, but I know the Navy was experimenting with "bubbled" hulls....To bad I can't get the air to stay......

    Oh yeah, my 460 is pushing [email protected] 5000....My CVX runs 55-60 any day, and hit 62 at Trinity one year. You should definitely be hitting 60+ no matter how heavy your hull is.

+ Reply to Thread

Quick Reply Quick Reply

Register Now

Please enter the name by which you would like to log-in and be known on this site.

Please enter a password for your user account. Note that passwords are case-sensitive.

Please enter a valid email address for yourself.

Please select your insurance company (Optional)

Log-in


Tags for this Thread

Digg This Thread

Posting Permissions

  • You may post new threads
  • You may post replies
  • You may not post attachments
  • You may not edit your posts
  •  
 

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95