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Carburetor issues

Discussion in 'Luhrs Yacht' started by DRL, Aug 31, 2021.

  1. DRL

    DRL New Member

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    Cape May
    Luhrs 290 Tournament owner, boat with 1995 Marine Power 350's / 5.7 CID motors (under 1400 hours). Recently changed from Holley to Edlebrock on recommendation from marine mechanic because Holley secondaries where not opening on port engine, motor would not go above 3300 rpms.. New Edlebrock carburetor ran well for about an hour, turning 4400 rpms then experienced loss of power... Changed fuel filter but needed carb cleaner to get engine running next day. Same issue resurfacing again, loss of power/no throttle response above 3300 rpms, pushing on a string. Any thoughts appreciated. Mechanic thinks I may need to drain and polish fuel, clean out port side fuel tank or problem will continue to reoccur. Any suggestions appreciated. Starboard engine runs like a champ with Holley carb.
  2. Capt Ralph

    Capt Ralph Senior Member

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    IMO, Fire your marine mechanic. He just wasted a lot of your money.

    Now you have a more complicated carb installed, performance may not match the other engine if it was running correctly and you have not a clue where the real issue now is.

    Holley vacuum secondary require lots of things before they open up.
    Testing secondarys in manual mode could of been easily preformed also.

    New failure could be anything.
    New fuel filters with new Carb?
    Anybody looked at the fuel quality at all before doing anything?
    Fuel pressure?
    Any diagnostics at all before part swapping?
    Last edited: Aug 31, 2021
  3. DRL

    DRL New Member

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  4. DRL

    DRL New Member

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    Thank you for your input but, well unfortunately not that easy. He's been a very good mechanic to date. I got into the boat knowing there were going to be some issues since the boat is over 25 years old. This mechanic has been very helpful in resolving several issues that were beyond my scope. Previous owner used "car" mechanics to make repairs and it was bad. As a for instance, this particular engine/alternator was converted to a single pulley system and didn't have the right specs for the alternator, some repair. Not only put on new pulley and right amp/voltage alternator, but had to replace the harmonic balancer which someone previously used the wrong length bolts to install, had to be drilled out. Replace the water pump as well. He's an old timer, knows I'm a retired vet and doesn't wash my wallet, in fact he seems to enjoy passing on his knowledge and will spend extra time just shooting the breeze and helping me understand certain mechanical issues that I am unfamiliar with.

    With the current issue, this port engine has never performed to the level of the starboard engine, always under performed and ran hotter. Diagnostics were done where he put a tach on the motors during trials, 400 rpm delta. Also, he recommended Atlantis Propellers and at the end of last season pulled props, good thing, they were completely out of balance. At the same time he replaced cutlass bearings (I saw how much play was in them) so props and shaft are in good working order. Replaced manifolds and risers on this same engine as it had a tendency to run hot, problem diagnosed by mechanic using thermal detector to id where the heat build up was. Changed 4" hoses all around, pulled out a chunk of the riser the size of my fist from where the hose connected to a 45 degree elbow. Changed spark plugs while the manifolds were off. And, yes, removed the old carburetor and the secondaries were stuck, carb was in bad shape. The flame arrestor was so clogged he literally had to burn out the gunk. We did check the fuel filter, no water, some sediment. Replaced with new filter. As I said, we had the boat out with both engines turning 4400 rpm, a first for me, nearly creamed my pants and at 60+ that's saying something. Ran it down the Cape May canal and made the turn by the ferry docks. As soon as we finished the turn the engine dropped power, couldn't get back over 3500 rms, sluggish throttle response, then it died out. Ran back on one engine. Next day got it started using carb cleaner and he manually closed carb and revved throttle to try and suck out impediments. Engine started and ran so so and that's when we discussed other issues including fuel since carb had a black tar like residue on visible parts of the casing. Going to replace distributor cap and rotor, pull carb and clean it, new kit and see what happens. Thank you again for suggestions, great forum!
  5. cleanslate

    cleanslate Senior Member

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    You have got junk in the fuel tank, IMO.
    You may have to drain tank completely. Dry it out inside, no gas..or fumes. Then cut in a tank access panel and really clean out the tank.

    OR replace the tank or tanks with new.
    I'm in CM too, have a CC Dory with the same motor 5.7 Crusader classic.
    Replaced my Holly a year ago with Edlebrock . Love it. It's been great right out of the box for me. I would say I have more than 100 hours on it. Holly was a P.I.A.

    Good luck.
    DRL likes this.
  6. Pascal

    Pascal Senior Member

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    I could be bad or dirty fuel but the filters should handle that.

    check the fuel pick up as well as the anti siphon valve on the tank. They get gunned up. Also how old are the fuel lines, they can collapse internally.

    if the previous owner used car mechanics make sure the fuel lines are marine USCG approved. Also check the alternators and starters to make sure they are ignition proof marine units. Distributors too

    finally make sure you have a gas fume detector in the engine compartment. It’s a must have in a gas boat along with the CO detector in cabin.
  7. Joe McKairnes

    Joe McKairnes Member

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    I was taught long ago - never change a part unless you've diagnosed it to be the problem - every time you touch something, you run the risk of adding new symptoms. Are both engines on the same fuel tank? if so, and one runs fine, it ain't fuel. Holly's are by far the best carbs. Vacuum sec's only come in when needed which is what you want on a boat. Sorry I cant be of more help!
  8. DOCKMASTER

    DOCKMASTER Senior Member

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    Ketchikan, Alaska
    If you suspect a fuel problem from port tank to port engine, why not run a simple temporary fuel line from the STBD tank to the port engine?
    Keep in mind, if you have bad fuel you may have already ingested trash in that new carb and may have to take it apart to clean it out. If you get trash into the needle/seat valve only way to clean is to disassemble. But you would think your fuel filters would prevent this.