420/44 DB Owners Club

This post deleted as OP removed his earlier post to which this referred...
 
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Ok, here's a scenario. You're on the hook sucking juice from your batteries trying to keep your Ben and Jerry's cold, you're naked because it's warm and you can't run the AC. You hear something strange. You jump out of bed to find you're dragging anchor and you're 2' from a rock wall. You run to the helm and start up the engines, but the voltage is low, so the engine cranks over slowly and then it hits a compression stroke and jams the starter and fries it. Ok, you've still got another engine but now you have even less juice in the batteries. So you run over and start your gen and let it run for an hour so you can start your other engine and avoid danger.
 
Quality Time....you cannot comment....you have a Dancer....wait,wait...so does Turtle .....how dare you both!!

Oh the humanity........
 
Alex

Sorry, I have nothing to add. I start my genny before leaving the dock and don't shut it down until I'm plugged in to shore power....but that's just me. To each his own.
 
I've added all you clowns to my s#@t list
 
Turtlesboat said:
Ok, here's a scenario. You're on the hook sucking juice from your batteries trying to keep your Ben and Jerry's cold, you're naked because it's warm and you can't run the AC. You hear something strange. You jump out of bed to find you're dragging anchor and you're 2' from a rock wall. You run to the helm and start up the engines, but the voltage is low, so the engine cranks over slowly and then it hits a compression stroke and jams the starter and fries it. Ok, you've still got another engine but now you have even less juice in the batteries. So you run over and start your gen and let it run for an hour so you can start your other engine and avoid danger.
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Mike,

It's a good scenario, but I think you very well know the answer to this one. Butm, here's my take on it:

1. Most boats setup in such way that the house doesn't drain all the batteries. In my 320 and 420 I saw one side being slighly higher charged after many hours of using 12v.
2. If the voltage drops below the level where the engine can fire up, then we have an issue. Either one used the batteries way too long or the batteries are no good and need to be replaced.
3. Each side has sets of 2 (my 320 and 420 had the same setting in that respect), so if you have one bad battery chances are the other one will help you maintain the load.
4. So, let's say it does happen and one side (2 batts) are too low. You start the side with normar voltage and use emergancy switch to shift the juice to the week side. You're ready to go.....

BTW, this scenario applies to any boat (diesel or gas), so the same preventive measures should apply to ensure good startup of the engine(s). I'm sure you've done it with your previous gas boats, just like I did. So, just b/c we have diesel boats now doesn't change the way we go about this sotuation.

P.S. I know some folks who startup their genny on GAS boats and don't turn them off until they reach the dock, b/c they don't want to be stock with dead battries. IMO, this is plain wrong, if you don't trust your batteries or the charging system you have a problem that needs to be addressed. So, running the genny in this case is just a temp patch on the bigger issue.

Just my .02c.
 
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My thumbs hurt.
 
Alex F said:
Mike,

It's a good scenario, but I think you very well know the answer to this one. Butm, here's my take on it:

1. Most boats setup in such way that the house doesn't drain all the batteries. In my 320 and 420 I saw one side being slighly higher charged after many hours of using 12v.
2. If the voltage drops below the level where the engine can fire up, then we have an issue. Either one used the batteries way too long or the batteries are no good and need to be replaced.
3. Each side has sets of 2 (my 320 and 420 had the same setting in that respect), so if you have one bad battery chances are the other one will help you maintain the load.
4. So, let's say it does happen and one side (2 batts) are too low. You start the side with normar voltage and use emergancy switch to shift the juice to the week side. You're ready to go.....

BTW, this scenario applies to any boat (diesel or gas), so the same preventive measures should apply to ensure good startup of the engine(s). I'm sure you've done it with your previous gas boats, just like I did. So, just b/c we have diesel boats now doesn't change the way we go about this sotuation.

P.S. I know some folks who startup their genny on GAS boats and don't turn them off until they reach the dock, b/c they don't want to be stock with dead battries. IMO, this is plain wrong, if you don't trust your batteries or the charging system you have a problem that needs to be addressed. So, running the genny in this case is just a temp patch on the bigger issue.

Just my .02c.
Click to expand...

Ok, here's a test. Hook up only one battery (to simulate a week or bad battery) and try to crank over a diesel engine. Have a spare starter on hand.

If you have a bad battery, say a bad cell in a battery, it'll probably screw up the good battery. I had a bad cell, 1 bad cell, in new batteries. my engine barely cranked over. For the life of me I couldn't figure out what was wrong. I had 12v but no cranking power. FW diagnosed it spot on.

And while you think all the house stuff runs on the house batteries, Shut off the other bank and you'll find a lot of stuff is running off that. So maybe you had a few glasses of wine, love is in the air and you collapse in bed and forget to shut off the cockpit lights.

The problem is, you're guessing how low the voltage can go before you can't crankover an engine. All of this while you're running around naked trying to fend off a rock wall. So during all of this, you're checking voltages on different battery banks trying to decide what order you're going to fire the engines in?
 
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Doug

I think most of the nakedness discussed was that of Captains....please tell us that is not the source of you professed "love"
 
Guys, I've been at the beach doin' my thing, so I'll admit to not reading this entire discussion. There are a couple of points that Alex may not be considering in his battery analysis:

1. You are drawing a parallel between the gas 320DA and the diesel 420DB as far as using the batteries for house current for extended time at anchor. It isn't going to work that way. You can crank a gas engine as long as you can get the motor to spin thru an intake stroke and a compression stroke then fire the cylinder off with a spark....9.5 - 10V will probably do it. Diesel don't work that way. You have to have enough reserve battery power to spin the diesel fast enough to develop enough compression to explode the fuel charge. Get much below 12.3-12.5 V and a diesel will grind and grind before it builds enough compression to fire off a cylinder. The reason you don't crank diesels on low voltage are mechanical not electronic. The wear and tear on the starter motor, the bendix, the ring gear and the relays or solenoids is significantly greater with low batteries. The other issue is washing out cylinders. When you crank a diesel with low voltage, you put several fuel charges into each cylinder before developing enough compression to fire a cylinder. The cold fuel literally washes all the lube oil off the cylinder walls and when the engine does start, it is doing so with no lubrication between the rings and cylinder liners. While using the generator may be a personal choice, don't save a dime now only to spend several boat dollars later repairing starting gear and refer to this post when your oil sample comes back with high iron content.....its from your cylinder liners. Always monitor your house DC voltage while you are anchored. When it get so 12.3 or so volts, fire up the generator and top off the banks before cranking the main engines.

2. You just think you are going to use the same battery bank vs. generator procedure with the 420DB as you did with the 320DA. I doubt it. Once your wife and kids enjoy boating in a greenhouse with all the exposed vertical glass, you will get weary of the " Can we turn on the air conditioner?" question. Sundancers may have that "cave" feel, but they are significantly cooler in the summer.
 
boating in a greenhouse with all the exposed vertical glass, you will get weary of the " Can we turn on the air conditioner?" question. Sundancers may have that "cave" feel, but they are significantly cooler in the summer.
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Amen to that! I step down from the salon to the forward (ie: underwater) section of the cabin after a week away from the boat and there's at least a 20 degree difference (cooler) down below.
 
That's why all the DA guys dress so nice and the DB guys run around in their underwear.
 
That could very well be. A typical late '90s 330DA, which is 35'10 LOA, has a single 12K BTU a/c unit. My old tub is 35'8" LOA and has a 16.5K BTU unit for the salon and 2nd stateroom, and a separate 7K BTU unit for the forward stateroom and head. And the 16.5K struggles in weather over 85 degrees.
 
fwebster said:
Guys, I've been at the beach doin' my thing, so I'll admit to not reading this entire discussion. There are a couple of points that Alex may not be considering in his battery analysis:

1. You are drawing a parallel between the gas 320DA and the diesel 420DB as far as using the batteries for house current for extended time at anchor. It isn't going to work that way. You can crank a gas engine as long as you can get the motor to spin thru an intake stroke and a compression stroke then fire the cylinder off with a spark....9.5 - 10V will probably do it. Diesel don't work that way. You have to have enough reserve battery power to spin the diesel fast enough to develop enough compression to explode the fuel charge. Get much below 12.3-12.5 V and a diesel will grind and grind before it builds enough compression to fire off a cylinder. The reason you don't crank diesels on low voltage are mechanical not electronic. The wear and tear on the starter motor, the bendix, the ring gear and the relays or solenoids is significantly greater with low batteries. The other issue is washing out cylinders. When you crank a diesel with low voltage, you put several fuel charges into each cylinder before developing enough compression to fire a cylinder. The cold fuel literally washes all the lube oil off the cylinder walls and when the engine does start, it is doing so with no lubrication between the rings and cylinder liners. While using the generator may be a personal choice, don't save a dime now only to spend several boat dollars later repairing starting gear and refer to this post when your oil sample comes back with high iron content.....its from your cylinder liners. Always monitor your house DC voltage while you are anchored. When it get so 12.3 or so volts, fire up the generator and top off the banks before cranking the main engines.

2. You just think you are going to use the same battery bank vs. generator procedure with the 420DB as you did with the 320DA. I doubt it. Once your wife and kids enjoy boating in a greenhouse with all the exposed vertical glass, you will get weary of the " Can we turn on the air conditioner?" question. Sundancers may have that "cave" feel, but they are significantly cooler in the summer.
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Frank,

Thanks a lot for providing such technial, detailed and logical explainantion. It was well worth to keep the discussion going to finally get response like this. You're 100% correct, I'm in the way comparing my 320DA gas with 420DB diesel. It's now much clearer to me that one of the major difference is that a diesel engine requires a lot more cranking power and the same drop in DC voltage on gas boat will not cut it with diesel boat.

fwebster said:
..... Always monitor your house DC voltage while you are anchored. When it get so 12.3 or so volts, fire up the generator and top off the banks before cranking the main engines......
Click to expand...

That is a great tip!!!


I guess in Mike's scenario, even though I'm able to fire-up the mains with the emergency switch it will not be a "healthy" startup and the engine may "pay the toll". I did not know this bofore this thread.
 
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rondds said:
Amen to that! I step down from the salon to the forward (ie: underwater) section of the cabin after a week away from the boat and there's at least a 20 degree difference (cooler) down below.
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Ron,

Do you use "HU" mode for A/C units or just crank up the temps to mid 80s in "Cooling" mode?
 
Alex
I shut down both units when I leave. The salon unit is the old three knobber (ie: not a digital panel). The forward stateroom panel is a smx II. I set that one to 74 degrees and leave it. Any lower than that it gets too chilly at night. The salon unit has a dial/knob for temp and I really never touch it. It is not graduated - just an hour which says COOLER. It's not pinned to the highest setting but it cycles at night and keeps the salon at about 74 degrees at night (measured by a digital thermometer).

I keep expecting to have to replace the salon unit but it keeps on chugging along. It's original and it does the job as it is supposed to... the air at the register is 20 degrees cooler than the air at the return. I think the problem is not enough registers - there are only two and all marine a/c units of that size recommend at LEAST three, with more being better. Another feat of SR engineering.
 
Yeah, it's amazing how much power it takes to crank these over. One little flaw and crawls over. I was pulling my hair out trying to figure out why I my port was barely turning over and my starboard had no issue. I would charge them up and the difference in voltage was minimal. I was ready to buy new batteries when Frank told me I had a bad Cell. Saved me a boat dollar in new batteries.
 
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