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Old 09-08-2007, 01:33   #16
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Hellosailor, if you think about how many times say a Truck starts every day, compare that to the boat and having starter and Alt wearing out is a non-issue in reality.
Wear on bearings etc are in fact reduced with more regular startups. This is because the oil is still up around all the parts. It doesn't take long for oil pressure to rise. Leaving the engine for a longer period only results in oil draining away from surfaces and the pump, which then takes longer to get the pressure up. Using a good oil and especially synthetic oil is good for maintaining a film around parts.
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Old 09-08-2007, 10:47   #17
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The fellow who taught me that, was a combustion engineer with mutiple PhDs, and Dean of an engineering school. He tuaght for pleasure not income, because he also owned patents on parts used in most of the railroad diesel-electric engines in the world.
I trust his expertise.<G>

"how many times a truck starts each day" Ever wonder why so many drivers leave it running for SO LONG even when they are in the yard waiting?<G>

Obviously the details will matter, i.e. your typical truck may be scheduled to be pulled from fleet service and overhauled every 100,000 or 200,000 miles. The sailboat engine is probably built from "lighter" parts, and never gets scheduled overhauls. Restarting intervals, thin film time...Synthetic motor oils probably didn't exist at that point yet, they've come a long way. Still, I like the idea of "no wear" versus "not much wear".<G>

With light enough use, sure, wear can be a non-issue. But every time you hit the starter, you throw spikes. Ever have a piece of electronics just "go bad" ? Spikes are often to blame--there's usually no protection against them except the breaker panel, everything that is not turned off, gets spiked. Last time I rewired a panel, I made sure to run spike protection (both zeners and transzorbs, and a little piezo alarm) on the leg that services the instruments. When and if the protective devices wear or fail, the little piezo will let us know. But no boat maker is going to spend the extra $25 to put that box on a production boat.

Spikes are enough of an issue that some alternator makers (for cars) now install spike protection IN the alternator, to clamp them before they can get out. The problem, of course, is that when they fail (and they will) the whole alternator gets blamed for failing too soon--when it should be celebrated as the "hero" that saved the rest of the electronics.<G>
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Old 09-08-2007, 14:23   #18
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A starter itself can not procuce a spike. The start solinoid can due to the collapsing magnetic field of the coil.
If a back EMF is created and can fry your electrical equipment, then your wiring is no good. The battery is of high enough resistance to sink any spike.
The same applies to the Alternator. The only time an Alt can spike is when it is instantly disingaged from the battery. Sometimes this can happen due to the key being turned off before the stop button/lever is pushed/pulled. The load being suddenly disconnected can make the voltage spike. The result is the output diodes being fried.
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Old 09-08-2007, 14:41   #19
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I won't argue when or how the spikes are created. I've just read, multiple times from multiple sources like Delco and ACDelco (the folks who used to build all of GM's electrical parts) and Cree-X (who sell a lot of those very birght and expensive LEDs for OEM light assemblies) that spikes of up to 200V are *routine* in automotive systems, and up to 600V in trucks, and that both starters and alternators are the cause of them.

These folks have no reason to tell me their products are causing spikes and spike damage--except to warn customers that failing to protect systems from spikes WILL routinely result in damage from them. They say the spikes are on startup, and while the battery makes a nice sink--it doesn't catch them all. Those nice LED taillight sets on Cadillacs and Mercedes, that can cost $1000 to replace? Expressly no warranty from the LED maker for that type of use, unless there is spike protection for those LEDs. Maybe they are just gunshy, but the protection is cheap enough so that I'll take their word. The chorus all seems to be singing the same way now that computer electronics have replace "electrical" systems.
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