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trich11trich11 Posts: 108Member ✭✭✭
I had our boat mechanic do a tune up which he completed today. Started the port engine and no change. Surprised because the cap and rotor was shot, he did a compression check. Number 3 has 60 lbs and 5 has ZERO! He is going to pull the head early next week and hopefully he will find a bad head gasket. If not, a new long block. This sucks.


  • 212rowboat212rowboat Posts: 2,132Member ✭✭✭✭✭
    Could be a broke rocker, pushrod, jumped timing from sloppy timing chain... Could be a lot of things.... Water in your oil?
  • Black_DiamondBlack_Diamond Holland, MichiganPosts: 4,342Member ✭✭✭✭✭
    If the head gasket was that bad, you'd expect water in the oil. Did he do a wet compression test? That will tell a lot.

    2003 342FV "Black Diamond", 350 MAG MPI, 20P 4x4 Props, PC BYC, Holland, MI
  • BabyboomerBabyboomer Louisville KyPosts: 918Member, Moderator mod

    Slip 866 Sunset Marina Byrdstown Tn
  • 212rowboat212rowboat Posts: 2,132Member ✭✭✭✭✭
    edited July 2013
    Compression tests can mislead.. a bit, anyway.. if the valve events are jacked up, the valve can be open which doesn't allow ANY compression.. if it isn't seated during the last 3/4 or so of the compression, it may allow SOME compression momentarily, but it leaks rapidly.. a leak down test, part of which is a compression both wet and dry, will tell you a lot without having to yank heads..

    If you yank heads, you may as well keep going..

    I've seen sloppy timing chains allow the timing between crank and cam to jump, which will foul valve event timing and show funky compression readings.. cross your fingers..

    I reckon I could look it up, but I'm mobile right now: I think these motors are non inference engines, which means the piston won't smack the valve no matter how jacked up the timing is..

    A indicator of jacked up shaft timing and fuel sync is seriously beat up rotors and rotor buttons... This is why I spill this on your page, and not just to give false hope.

    Btw: head gaskets blown enough to not allow compression are going to expose the water jacket passages, which will leak into the crankcase- there is no way around that... Look in your crankcase for milkshake.. if none, you've got reason to rejoice. :-D
  • frodo13056frodo13056 Channahon, ILPosts: 210Member ✭✭✭
    Geeze - before I yanked the head, I'd darn sure to rotate the crankshaft by hand and watch to see if cylinder #5 valve train is in good working order. You need to remove the valve cover to get to the head bolts so there is no additional work to be done. And, I'd also borescope the cylinder by removing that cylinder spark plug and see what you can see. Borescopes are pretty inexpensive these days. Typically, valve train component failures occur after high RPM situations - excessive RPM or extended high RPM runs and typically, you can hear valve train clatter just by listening close to the valve covers or by using a stethoscope type device. I usually just take a screw driver, place the metal end on top of the valve cover and lean in and place the handle next to my ear - it's pretty amazing how sound travels. There are a few situations where a valve could get stuck open creating a loss of compression and that usually would be a bent valve stem or a bad valve guide - both would require the head to be removed to repair. As everyone has mentioned, blown head gaskets usually result in water in the oil. Good luck!
  • trich11trich11 Posts: 108Member ✭✭✭
    Thanks for the replies. I have a fair amount of trust in my guy but your questions/thoughts have merit and I will ask them before any repairs commence. Someone else in the marina told me someone had recently ordered a long block to the tune of $3800. Does that sound correct?
  • 212rowboat212rowboat Posts: 2,132Member ✭✭✭✭✭
    Yup.. that isn't a bad price for a marine engine.
  • AlswaggAlswagg Posts: 2,276Member ✭✭✭✭✭
    Long block brand new for $3,800.00????  I would hope so.  I usually sell a New Vortec Rotating assy for $3,500.00    Stay away from Jasper rebuilds or any other rebuilder who will use engines which are from Salt water environment.  I have not installed a rebuild engine for many years, why when a brand new is same cost or even cheaper????   Al
  • raybo3raybo3 Revere MAPosts: 3,775Moderator mod
    Good luck trich hope all works out for you...
    2002 342 Fiesta Vee PC Point Of Pines YC Revere MA.
  • trich11trich11 Posts: 108Member ✭✭✭
    Looks like it's a bad head gasket and one "Tuliped" valve.
  • brianluckbrianluck baltimore marylandPosts: 174Member ✭✭✭
    Ill take a head gasket over an engine anyday
    1994 300fv "General Madness"
  • 212rowboat212rowboat Posts: 2,132Member ✭✭✭✭✭
    trich11 said:
    Looks like it's a bad head gasket and one "Tuliped" valve.
    no way... it's more than that for certain... blown head gaskets don't cause valves to smack, and smacked valves don't cause head gaskets to give.....

    I'd wager you need a timing chain/belt/gear- whatever flavor...
  • Black_DiamondBlack_Diamond Holland, MichiganPosts: 4,342Member ✭✭✭✭✭
    edited July 2013
    Could be a failed valve spring or retainer. I agree though, it's more than what you said. Looking into this more it looks like not rare on a mercury marine engine: over heated combustion chamber is the cause, esp from lugging the engine.

    2003 342FV "Black Diamond", 350 MAG MPI, 20P 4x4 Props, PC BYC, Holland, MI
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