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Engine Run-on & Hesitation

Discussion in 'Boats and Motors' started by Johnny Bravo, Jun 6, 2005.

  1. I have a 1996 Mercruiser I/O. I bought the boat used, but I believe it was not used for quite some time and the engine has very low hours. Runs great but about 10% - 20% of the time the engine runs-on after you shut it down. It just turns over a couple more times. Also, there is a slight hesitation about 1/3 of the way through the throttle range. It only occurs if you throttle up at a medium pace. If I throttle slowly or floor it, there is no hesitation. I thought maybe the fact that it sat idle for an extended period may have allowed for some build up to accumulate in the engine.

    I've heard of this problem with car engines as well due to build up in the pistons/valvetrain. I know in cars there is a fuel system treatment that you can run through to correct the problem. Anyone heard of such a thing for boat engines? Hopefully a simple additive can help the problem without tearing into the engine. Any suggestions???

  2. Plain old fuel injector cleaner should help ;)

  3. Thanks. I'm assuming that's just poured in to the fuel tank, correct?
  4. mrfishohio

    mrfishohio Recovering Fishaholic

    There's a product called Sea Foam that has great results in some situations. Made for boats, most auto parts have it. Some carb cleaners aren't really for 2 cycles, no problem for 4 the bottles.(desolves the lube oil in the fuel)
  5. You are talking inboard,correct?If so fuel injector cleaner in the tank,2 cyl outborad what Jim said :)
  6. It's an I/O. I'm not by any means an engine guru, but I believe the Merc 3.0 has a carb. Would fuel injector cleaner really do anything to help it?
  7. Yes I put it in any 4 stroke with any age on it ;)
  8. ncraft150

    ncraft150 Buckeye-Basser

    The I/O mercruisers are basically car motors. Most fuel injector cleaner also says for carbs on the bottle.
  9. Hetfieldinn

    Hetfieldinn Staff Member

    Try the Sea Foam idea first. I've been using it for years. It works great. You can get it at NAPA, Wal Mart, and Gander Mt.

    It's about $4 a bottle.