Engines

[oldsalt]

On my 10 year old car diesel, I turn the key for instant starting, and turn it again to stop the engine. On my 3 year old boat diesel, I need to use preheaters before starting, and must not stop it with the key as I can damage the alternator, instead I have to press a different button.

Why the difference in operation?

 

[yoda]

What car is it, it's unusual for a diesel car not to have glow plugs. As for stopping a diesel car the difference is that there will be an electrical hold open mechanism somewhere that is not fitted to a boat engine. When you deenergise the ignition it effectively does the job of pulling the stop cable for you. Just another thing to go wrong in the marine environment.

Yoda

 

[tr7v8]

Heater plugs are not used on all diesels, depends on whether direct or indirect injection. And I can never remember which one, lot of moder trucks don't have heater plugs. Switch off on key is just a solenoid which is held open when engine running and closes when gnition switched off. Which is fine till it dies and engine won't run.

Jim
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[aztec]

your car probably has automatic heater plugs, switched on by a relay with a timer, your boats ones , you need to press and hold a button for 20 seconds? or hold the key in the heat position for the same amount of time. some use thermo-start which is similar but uses a coil, and diesel to create a fire in the inlet tract.

i suspect your car has a light flywheel, which when you turn off, allows the engine to stop quickly, stationary/generator/ boat engines can use a heavier flywheel as responsiveness is not an issue, there fore the engine will run down instead of stopping instantly, this in some cases can coause the slip rings in the altanator to become glazed, reducing its efficiency.

or i might be talking crap, as i have found out with this type of post before.. but hey no ones perfect (except byron)

good luck, steve.

 

[dickh]

Heater plugs are always used on Indirect Injection, which is most diesels fitted in boats.
All my previous cars, Citroens, were Indirect Injection so had heater plugs, but my current one, Peugeot HDI diesel is Direct Injection Common Rail so starts instantly. Some later car diesels had fast heat up heater plugs - 2/3 secs so was almost instant starting(my partner has one of these but always forgets to wait the 3 secs and just turns the key - just takes a second or two longer to fire).
Cars have electric solenoids for fuel stop so stop as soon as ignition turned off - most boat engines have a 'pull to stop' cable as the engines are usually converted industrial engines where electric stop solenoids are an expensive add on.
But can't see why automotive type electric stop units aren't fitted to boat engines except that these are usually built into the fuel pump, which you don't normally get on Industrial Diesels.


dickh
I'd rather be sailing... /forums/images/icons/smile.gif

 

[Plum]

The basic difference is complexity. On cars the glowplugs and preheat devices are controlled by temperature sensors and timers so the driver does not have to do anything other than turn the key (or at worse, wait for a light to go out before cranking), and the turning off of the "ignition" key activates an electromechanical solenoid that shuts off the fuel to stop the engine.

You could have all the above features on a boat (a few do) but it add complexity and reduces reliability. It is usually all the electrical timers and solenoids, and the associated extra wiring, that is more vulnerable to the damp and salty environment on a boat engine. Yes, you can have all the bells and whistles on your boat engine while maintaining the same reliability, but it requires better design and materials and therefore a higher cost/price.