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Thread: 4400 rpm last year 3800 this? Help

  1. #1

    Default 4400 rpm last year 3800 this? Help

    was running 4400 wot last year to get on step this year I can only manage about 3800 wot and the boat doesnt get on step as fast. I got new staters and had silver streak in ancor town touch up my impellors. I've got a 3 stage hamilton with a 1XL-19-22 same as last year but I just cant get the motor to turn up. Also I am having to run at 3400-3600 to run with any speed at all where last year I could run at 3000 with no problems. I have a chevy 350 with a rv cam that is supposedly pushing 350 HP last year I would have said yes it is this year I just dont know. This motor only has about 60-70 hrs on it from a complete rebuild. So I was told. I'm not so concerned with the rpms I just want to get out of the water faster. I have a total of 3 22's and 3 19's degree impellors at my disposal.HELP HELP HELP is the problem my jet or the motor. I am only using about 7/8 of my full throttle but it was the same last year I changed nothing...Help

  2. #2
    Member broncoformudv's Avatar
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    Are you sure your impellors are in correctly? I have heard of guys putting them in backwards and having similar issues.

    What size and type of boat do you have?

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    Member Akgramps's Avatar
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    Did you take it back to Silver Streak and have them look at it?

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    Member Tolman24's Avatar
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    Did you take everything out and only put back what you need. It is easy for the boat to gain weight each year, kind of like us. I took about 150 lbs of crap out of mine at the start of the year.

  5. #5
    Member broncoformudv's Avatar
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    Quote Originally Posted by Tolman24 View Post
    Did you take everything out and only put back what you need. It is easy for the boat to gain weight each year, kind of like us. I took about 150 lbs of crap out of mine at the start of the year.
    I thought they were supposed to keep gaining weight? Isn't that part of two footitis?

    "See baby the boat really is getting old and worn out it won't pull such and such rpm anymore and takes a football field to get on step." "Now don't you agree we need that new bigger more powerful boat?"

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    Member SusitnaAk's Avatar
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    I would have a look at the carb. Let somebody else drive and watch for your secoundarys to open? Also I would check the timing, Make sure it is advancing Get a book or Ck with the guys on River Jet forms for the spec, on the 350. Something like at 3000rpm it should be in the 30s advanced, Make sure the plate inside the dist.. is free and not gummed up, goes for the weights inside there to! Also a bigger nozzle at the back of the jet will bring up the rpms and move more water, up on step faster, but would lose little on the top end,

  7. #7

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    The boat is a 22 foot silver streak. and I have looked at and seen the secondarys open up. Not sure on the timing or the cap issue but the motor runs great no shakes smooth doesnt hesitate at all. Now the impellors in backwards.I will definetly look at those. When those slide on the shaft one of the faces on them is solid and the other is kinda hollow. Which should face the motor? Right now I think the solid side is facing the motor. The side with the numbers on it. thanks again guys with this thing burning 25 gallons an hour right now I'll have to sell my kid to fish...

  8. #8
    Member Magnum Man's Avatar
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    Default jetboat

    Things I would look at are cap/rotor/recheck timing and firing order?
    bad plug wires
    a vacuum leak on the carb base gasket or in the intake manifold
    sticky elec choke
    stuck float in the carb
    water in the fuel filter
    compresssion check
    buuut........ almost sounds like your impellers ar backwards or in the wrong order.
    If you have a right hand rotation motor the leading edge or the sharper edge of the impeller will be on the left side if you are at the stern looking to the front of the boat

  9. #9
    Member akshrop's Avatar
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    Check your impellors. I had the same problem last year and it was the impeller.

  10. #10

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    just got done tearing down the jet and all that looked good. all impellors are in the correct way. Will pull plugs and wires this afternoon as well as a cap, button and new rotor. will let al know the out come. Hey guys thanks again

  11. #11

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    guy at Napa said the plugs looked as though the motor was running rich.. Could this be the problem?

  12. #12

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    Could be. For jet boats the general rule is that if your RPM's are low at WOT then it is an engine problem, if you get full RPM with less than full throttle then it is a pump problem.

  13. #13

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    Quote Originally Posted by akdube View Post
    guy at Napa said the plugs looked as though the motor was running rich.. Could this be the problem?

    At 25 gallons per hours I would say that it is running really rich...and it making you really poor in the process. Check things in this order

    1.) take it back to the guys that worked on it and make them stand by their work

    2.) compression - make sure that each hole is within 10 percent of each other. On a mild 350 I would estimate somewhere between 130 psi to around 150 psi depending on lots of things. Make sure you pull all the plugs before you do it. It will not do any good to jump down and do anything else unless you know that the compression in this engine is strong.

    3.) timing - you should have around 8 degrees at an idle and as you accelerate the engine with the timing light on the timing mark, it should advance the timing accordingly. If it doesn't then you need to repair the advance weights in the dist.

    4.) carb - you don't know how many motors that I had worked on when I still turned wrenches professionally that were all pretty and nice looking fresh rebuilds that had 20 year old carbs on them. Simply put - they just don't last that long very often and chokes that are this old love to stick closed. If you carb is an old clunker just pony up and get a new one. Judging by how much fuel you are using and that you plugs look like they were dipped in gasoline, I would think that this is most likely your problem. If you carb is "newish" take it apart to check to make sure that the float, needle and seat, and every thing else looks clean. If you get this far, it wouldn't hurt to clean it out thoroughly with carb cleaner.

  14. #14

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    just went for a cruise with a mechanic. The secondary is opening up and it is getting fuel. BUT he pulled my distributor and I guess my button was "sloppy" meaning he could move it a quarter inch each direction. He adjusted it best he could and is ordering a new button. but this seems to be the problem got it to 4200 rpms. And with the new impellors he said I may lose some rpms as they are biting the water better. When the button shows we will replace and adjust timing with a light... sound right? GOD i hope so... thanks

  15. #15
    Member Akgramps's Avatar
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    Did you ask Silver Streak for help or are you done with that?

  16. #16

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    I asked and called Ben several times and he was very helpful everytime I talked with him. But for what he did to my boat, new staters and tuned the impellors. I did not feel right trying to put this on him. If I truely thought it was his doing then I would have but I did contact him and he was helpfull. Thanks for inquiring on that.

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