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Thread: 5.7L ski Boat is being a cunt. TBI conversion?

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    Registered User burn is weird's Avatar
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    5.7L ski Boat is being a cunt. TBI conversion?

    Hey Guys,

    Got a carbed 5.7 350 magnum mercruiser ski boat and its been running like a cunt the last few times we've taken it out. hard starting hot and cold, idles shit and black smoke galore, carbs are black magic and witchcraft to me so I'm considering putting a TBI (throttle body injection) kit on it rather than getting a boat mechanic to pull and rebuild the carb (every bill is $1k it seems, so B.O.A.T is literal)



    http://www.ebay.com.au/itm/EFI-Compl...-/321764729811

    the kit comes with everything including throttle body and adaptor plate, ECU, loom, an O2 sensor adapter plate to run in closed loop, has knock sensor and water temp/tps etc.

    I would expect it to run better, start better hot/cold with no vapor lock problems and use less fuel. is this realistic? or am I better to just stick with the carb, as the good chevrolet lord intended.
    Last edited by burn is weird; 18-04-17 at 12:44 PM.

    Oo___oO


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    Registered User Milkman Don's Avatar
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    5.7L ski Boat is being a cunt. TBI conversion?

    What road motor are they based off? (Iron block truck LQ9?) The old man had a mercruiser v6 4.3 that looked like an ecomoo with marinised heads/exhaust.

    I don't see why you couldn't use one of those Holley or similar kits the Roadkill guys have thrown on a few cars now. I'm guessing similar to the one you have posted.

    Boating needs to be enjoyable and if you need the thing to start at hit of the key you damn well want it to fire in normal or emergency situation. I'd get something that offers a well known tuning system that opens your window of self tuning or getting someone to spend a day on the lake with you.
    Quote Originally Posted by Faux Forg View Post
    I agree with Rdyno

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    Goat roper Motherfucker Jones's Avatar
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    Hit the needle and seats gently with a hammer. I'm not joking. Sounds like it's just flooding. Make sure it's got a filter and the tank isn't half full of water for starters.

    I'm sure a wiztard cunt like you could learn how to do a rebuild on a Holley. They're basic as fuck. TBI is pretty much an electric carby anyway and not known for any kind of performance. Evidenced by the fact it has half the throttle blade area of a 4 barrel carb. I can't see you getting major improvements over a properly working carburettor.
    Last edited by Motherfucker Jones; 18-04-17 at 12:53 PM.
    Quote Originally Posted by RVK 355 View Post
    Hold it flat cunt

  4. #4
    Registered User burn is weird's Avatar
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    its a 4 barrel Rochester Quadrajet if that means anything

    Oo___oO


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    Goat roper Motherfucker Jones's Avatar
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    Yeah that means give it to someone else to rebuild lol.

    They are a good carb as far as something you can set and forget though. Get someone who is good with them to rebuild it and you'll probably be good for another 10 years. They also give a good balance of performance and economy. Not as simple as a Holley and have some tricks though so probably not a great DIY project for someone who is a carby hater
    Quote Originally Posted by RVK 355 View Post
    Hold it flat cunt

  6. #6
    Registered User burn is weird's Avatar
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    watched a video on rebuilding a quadra, looks pretty easy really as long as you're meticulous with measurements but I'm sure that's like watching someone bake macarons on youtube and then trying it yourself.

    Don't hate carbs, just never used one and haven't spent the time to read up on how all the circuits work and what all the little doohickeys do other than fucking around with mixture screws on an outboard/mower until it runs ok.

    A bit like not knowing/learning how to build a mud hut when reinforced concrete is now available.

    had a bit of a google, and an alternative is to ditch the quadrajet and put an edelbrock 1409 marine carb on it. can buy one for about 350 usd and most people say they're plug and play with a bit of idle screw fiddling, a new fuel line and wire up electronic choke and are a good thing

    boat engine is only in the vicinity of 260-280hp so pretty much anything should do the trick.
    Last edited by burn is weird; 18-04-17 at 04:02 PM.

    Oo___oO


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    Registered User Milkman Don's Avatar
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    That's my second opinion, ditch the old carb for something modern
    Quote Originally Posted by Faux Forg View Post
    I agree with Rdyno

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    Purist, whats that? Jason Broadhurst's Avatar
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    EFI is hard yakka. Don't overlook fuel pump, filter, lines, wiring, CAS. You also have to ensure it's pretty reliably installed and commissioned. Paddling sucks dick.
    Jason Broadhurst

    Someone once asked me if they could use my mower. I said "sure, so long as it doesn't leave my yard"

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    Registered User 9triton's Avatar
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    Quote Originally Posted by Motherfucker Jones View Post
    Hit the needle and seats gently with a hammer. I'm not joking. Sounds like it's just flooding. Make sure it's got a filter and the tank isn't half full of water for starters.
    don't hit the Viton tipped needles though ....

  10. #10
    sack riding 10sec rx7's Avatar
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    Quote Originally Posted by Jason Broadhurst View Post
    EFI is hard yakka. Don't overlook fuel pump, filter, lines, wiring, CAS. You also have to ensure it's pretty reliably installed and commissioned. Paddling sucks dick.
    i put efi on my ski boat 10 years ago, i havent touched it for 8 years.. just starts and runs every time
    im a cunt
    and apparently i dont know shit...

  11. #11
    Registered User Milkman Don's Avatar
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    Quote Originally Posted by Jason Broadhurst View Post
    EFI is hard yakka. Don't overlook fuel pump, filter, lines, wiring, CAS. You also have to ensure it's pretty reliably installed and commissioned. Paddling sucks dick.
    So does trying to start a unstartable carb. Never know what situation you may be in
    Quote Originally Posted by Faux Forg View Post
    I agree with Rdyno

  12. #12
    Registered User dnegative's Avatar
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    If you let both sit for extended periods the EFI setup will be even more of a cunt and fuck I'll take a dodgy carb fucking out over a CAS dying 20km from shore. You can always pour fuel or spray deodorant into the cunts, you cant put magic smoke into sensors.

    If you got the Quadrajet rebuilt and you run the thing semi regularly its going to be reliable;
    Or just put a Holley on it and keep a spare brand new one on the boat with a spanner and screwdriver? lol
    Last edited by dnegative; 18-04-17 at 09:13 PM.
    Quote Originally Posted by cracka View Post
    Fuck I'm retarded

  13. #13
    Registered User Marlin's Avatar
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    The QJ is a good match for them and super safe and reliable. They're not hard to put a readily available kit through them either, just some caution not to bend needles.
    You sure it's carb though? Not one of the other dozen or so issues that can arise? It's not backfilling water through rotten risers causing a misfire for instance?

  14. #14
    Registered User burn is weird's Avatar
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    Will spend an evening this week ruling out the other possibilities before jumping in the deep end with new major parts.

    cheked a few things at the ramp to rule out the basics.

    water sep filter wasn't full of water but could be rooted I guess, siphoned from bottom of tank and didn't get water out either. that was my first guess as it's happened before and ran like crap
    ignition and plugs are all in good shape
    fuel pump pressure is adequate

    only thing left is the carb. but what about the carb is the bit I don't know about.

    I'll drain the tank and try some fresh fuel. might have been country servo fucked fuel?

    Oo___oO


  15. #15
    Registered User burn is weird's Avatar
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    Forgot about this thread... A bit of closure. Pulled the carb down and the float valve seat had completely unscrewed itself from the housing bar o e thread so the bowl was filling up and there was a bunch of shit jamming the power valve open at the bottom of the bowl.

    Watched a YouTube video and put a kit through the carb and now she's apples. Wasn't nearly as bad as I was expecting. But now it's winter. Fuck. Oh well we'll be the only boat on the lake!

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