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  1. #11
    Join Date
    Dec 2002
    Location
    Gloucestershire
    Posts
    5,384

    Default Re: Engine won't rev

    A bit more investigation.

    I detached the prop shaft from the gearbox at the drive flange and, with forward gear engaged, revved the engine. It reached normal 2000 + as it does out of gear. At the same time. with better access and leverage than before, I turned the prop shaft. It was stiff and could not be described as free. There seemed to be an intermittent, once per rev, increase in the resistance. This afternoon I will dive and have a look, if I can find space amongst the weeds! I have a Fat Max saw (by Stanley) that is like a miniature sabre. Bought it on impulse but never found a use for it. This could be an ideal baptism.

    However, pondering through the night (an unfortunate habit), it seems that the engine is not struggling to accelerate. It just seems happy with the speed it is at. That suggests, maybe, as someone has pointed out, it may be a governor problem.

    Saturday morning, an expert friend has promised to have a look.
    I'd rather be naked
    www.mastaclimba.com

  2. #12
    Join Date
    May 2001
    Location
    North Wales, sailing Aegean Sea or Menai Strait
    Posts
    21,966

    Default Re: Engine won't rev

    It should be very easy to turn your prop shaft. The problem could be external as you suspect, prop fouled by something for example, or it just might be the Aquadrive bearings. I assume whatever stern gland you have has not been touched? It is certainly possible to over-tighten a packed gland.
    Answers to some technical queries at new website http://coxeng.co.uk

  3. #13
    Join Date
    Jan 2011
    Posts
    5,753

    Default Re: Engine won't rev

    Sounds to me like you need to get the propshaft running freely and try it again, before doing anything with the engine.

  4. #14
    Join Date
    Dec 2002
    Location
    Gloucestershire
    Posts
    5,384

    Default Re: Engine won't rev

    Quote Originally Posted by vyv_cox View Post
    It should be very easy to turn your prop shaft. The problem could be external as you suspect, prop fouled by something for example, or it just might be the Aquadrive bearings. I assume whatever stern gland you have has not been touched? It is certainly possible to over-tighten a packed gland.
    I had a look under the boat yesterday afternoon (forgot the wetsuit but wasn't really cold!).

    There were just a few strands of weed and the prop turned easily. The lack of leverage in the boat probably was the cause of the previous apparent stiffness.

    The gland is a Deep Sea Seals one, i.e. ceramic disc to bronze, no tightening required.

    Suspicion (don't really understand enough for more than that) now centres on the injector pump. This was recently professionally rebuilt. The engine doesn't emit clouds of smoke or struggle. It just seems happy with the revs it achieves. I don't understand how the governor works but that could be the cause (as someone has suggested). I have a spare pump and may swap them over. The access is abysmal.

    Tomorrow expert friend has promised to attend and I will report back.
    I'd rather be naked
    www.mastaclimba.com

  5. #15
    Join Date
    Jan 2004
    Location
    Portsmouth
    Posts
    2,733

    Default Re: Engine won't rev

    Do you know if it used to rev OK in gear? - I'm wondering if it has a way oversized prop

  6. #16
    Join Date
    Dec 2002
    Location
    Gloucestershire
    Posts
    5,384

    Default Re: Engine won't rev

    Quote Originally Posted by Aardee View Post
    Do you know if it used to rev OK in gear? - I'm wondering if it has a way oversized prop
    The prop and the engine are as dictated by the hull designer. If the prop was too big, I would have thought the engine would have laboured and chucked out smoke. It doesn't. It is quite happy to "chug".
    I'd rather be naked
    www.mastaclimba.com

  7. #17
    Join Date
    Jun 2013
    Location
    scotland
    Posts
    203

    Default Re: Engine won't rev

    Before condemning the injection pump and removing it, get yourself a small container of clean diesel and pipe it directly to the fuel intake of the injection pump, a priming bulb in the fuel line would make things easier. Then try the engine. Yes fuel will return to the main tank and not your temporary container but it will give you enough time to determine if the pump is at fault. You may have symptoms of fuel starvation, using the container will take the fuel supply and filters out of the equation. Also some pumps may have a small wire gauze in the intake pipe at the injection pump, take pipe off and have a look, you probably don't but just to make sure. If you can't get a priming bulb just pipe it without one, the dpa has its own supply pump.

  8. #18
    Join Date
    Jun 2005
    Location
    South West
    Posts
    610

    Default Re: Engine won't rev

    Quote Originally Posted by Bobc View Post
    ........Have you checked things like the air filter and fuel filter. Usually all a diesel needs to run is fuel and air, and denying the engine of either one will kill it.
    +1 for the air filter.
    I can't see a reply that says you have tried taking off the air filter - I don't know your engine but a long-clogged air filter gave me similar symptoms once.
    Cheers
    Bob
    Trying not to extrapolate from zero

  9. #19
    Join Date
    Jun 2019
    Posts
    54

    Default Re: Engine won't rev

    You said the prop was free on the hard so I assume you have just been lifted in.
    Did they have a strop in the wrong place and its bent/ moved the shaft.
    I would think the engine is fine as it revs freely off load and you seem to think the shaft is a little stiff so that would be my area of thought. No mention of what happens in astern?

  10. #20
    Join Date
    Dec 2002
    Location
    Gloucestershire
    Posts
    5,384

    Default Re: Engine won't rev

    Quote Originally Posted by Aardee View Post
    Do you know if it used to rev OK in gear? - I'm wondering if it has a way oversized prop
    The engine and the prop were as specified by the designer. Straight after launch, it seemed ok but then I'm an old git with failing memory!
    I'd rather be naked
    www.mastaclimba.com

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