Converting to Diesel, What about cut out switch?

Discussion in 'DIY Marinizing' started by nksky, Aug 18, 2010.

  1. nksky
    Joined: Aug 2010
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    Location: Ireland

    nksky New Member

    Hi Folks,

    Fantastic forum lads, very interesting.

    Anyways, I have a 18ft Searay fitted with a 4.3v6 Mercruiser with an Alpha Gen2 outdrive. I now want to convert this to diesel, basically for two reasons, save on fuel costs, plus the excessive price of mercruiser parts in Ireland.

    I am going to use a 1.9TD VW engine, probably with a closed cooling system. My question is on the the 4.3 the shift plate, there is a microswitch there that briefly stalls the engine while you shift from forward to N to Reverse etc, to prevent gearbox damage.

    Does anybody have any ideas on how I might figure this out on the new diesel setup. Thanks.
     
  2. WestVanHan
    Joined: Aug 2009
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    WestVanHan Not a Senior Member

    nsky,your first post this should go in the marinising section,someone will move it...

    I'd hazard a guess that it may work to hook into the tdi "ignition" switch..but I wouldn't just start goofing around with it.

    With a digital tach check accurate idle speeds of both...when the v6 switches off to see it's lowest rpm.
    Maybe the tdi idles low enough to not require a shutdown..or maybe it can be idled down enough to work??
     
  3. CDK
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    CDK retired engineer

    The 1.9TD has an electric fuel shutoff valve that can be wired to the kill switch.
     
  4. anthony goodson
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    anthony goodson Senior Member

    CDK good morning ,with your intricate knowldge of this engine ,would it not be a mercyful act to make nksky aware of the perfomance shortfall he will experience.
     
  5. CDK
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    CDK retired engineer

    Yes it would Anthony, but I think this is only the beginning of an interesting conversation.
     
  6. nksky
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    nksky New Member

    Well lets get started....... Having read through a large amount of these forums, I thought that the vw 1.9td engine seemed to be the engine of choice, I am aware that the power will not match that of the 4.3 petrol engine, but will the difference be that great?

    Will I not benefit from a lighter engine to give a higher power to weight??

    Trying to buy a Mercruiser engine in Ireland is expensive, nobody doing re-cons and if you buy in from the states etc, the tax man likes to take a nice chunk off you. Petrol at the moment €6 or $8usd (avg).

    Right back to engine choice, I have other options, but then weight comes back into the equation,

    2.5 Diesel Ford Transit Engine, Maybe a mitsubishi pajero 2.5 engine.??

    I`m wide open to suggetions here, didnt the audi/vw group do a 2.5TDI engine?
     
  7. anthony goodson
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    anthony goodson Senior Member

    How much is diesel in Ireland ? ,remember it is now illegal to use lower taxed red for marine leisure propulsion. Look again at your cost/benefit analysis of diesel. owing to political intervention it is no longer a no brainer.
     
  8. CDK
    Joined: Aug 2007
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    CDK retired engineer

    The 1.9 TD produces 68 hp @3700 rpm (type ABL). It can be tweaked to deliver more than 100 hp for a few minutes but not longer because there is an oil temperature issue.
    There also is a 5 cyl. delivering 78 hp (AAB).

    All more powerful VW diesels like the 102 hp (AJA) have direct injection and electronics. There are even 1.9 TDI engines doing 130 hp in an Audi A4.

    The problem with all TDI engines is that you need the ECU and associated wiring. Engines salvaged from crash vehicles come without ECU so you'd have to buy that separately which may prove to be very expensive.

    Lancing marine's favorite diesel for conversion is the noisy 2.5 Transit engine, which delivers 130-140 hp.

    Before contemplating Japanese engines, check the availability of a water jacketed exhaust manifold.
     
  9. Northwester
    Joined: Sep 2007
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    Northwester Junior Member

    The shift interuptor switch on Mercruiser Alpha sterndrives (also known as the stall the engine switch when not working properly) is used to ensure that the operator of the vessel can take the drive OUT of forward or reverse gear into neutral. It is not used when the vessel operator shifts INTO forward or reverse from the neutral position.

    My stern drive mechanic tells me that on with 4 cylinder gas engine, it is possible to shift into neutral without using the switch but with a 6 cylinder or 8 cylinder engine, it is not possible to do so. This suggests that one might be able to get away without using it with a low HP application.

    Modern sterndrive designs with cone clutches i.e. Volvo, Bravo I, II or III do not require this feature. Only the pre-historic design of the Alpha drives with dog style clutches require this feature.

    I have two Alphas on my boat and I have to keep the switches in good adjustment to ensure I don't stall at the worst possible moment.
     

  10. CDK
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    CDK retired engineer

    He is wrong. The stress on the shift cable determines whether or not the switch is activated. When throttling back fast enough on a 300 hp V-8 the switch doesn't work, but when manoeuvring carefully in a crowded marina even a straight 4 cyl. needs it. That's why it always stalls the engine in the worst possible moments.
     
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