Marine vs. Auto Motor....

[DickDanger]

This may be a weaka$$ questions, but would anyone except anything more from me anyways???? Why is it that a 454 BBC in a boat seems to draw more battery power than a 454 BBC that is in a truck? I know that there are some differences, but have always wondered that. -DD Out

[DerangedToo]

How is it that you are checking for current draw? My only guess would be that in most vehicles the ground cables arent as long? So with a longer cable you would have more resistence , there fore more current draw??
Just a thought...
Deranged Out...

[cruser]

Sorry, more resistance means less current, with the same voltage applied.
The only difference that I know of that might cause more current draw on the water is that boat motors turn higher rpms requiring more current to support all those little spark plug induced explosions.
Seems like there shouldn't be a lot of difference though. just a few amps.
curzer

[rmclague]

Sorry, more resistance means less current, with the same voltage applied.
Right, More resistance means less current available, but means more current draw to support the same demand.
At least this is my understanding, and i am pretty confident that it is right.
Rob

[Blown509Liberator]

Ohm's Law & Kirchoff's Theories
Ohm s says the Voltage ie equal to Resistance times Amps.
So if we have a circuit that has 12volt source and 6ohm's of Resistance amps will equal 2 if we increase the resistance to 12 amps equals 1.
Now look at Kirchoff's Theories
In a Series circuits he states:
Total current flow is the same at any point.
Some of all voltage drops will equal source voltage (i.e. 12v source with two 6ohm resistors pulling total of 1 amp , each resistor will consume 6 volts.. amps x Resistance = 6v)
Sum or all resistance will equal total cicuit tresistance.
Parallel Cicuits
Voltage is equally applied to each branch
Sum of the current flow in each branch is equal to the total current
Total resistance of entire circuit is always less than the lowest resistance in any sigle branch.

[Rivernut]

When running they should be the same. I question your judgement on this. The batteries are different though. Marine batteries are rated in "marine cranking amps" not "cold cranking amps" like for cars. The difference is that the marine batteries are rated at a higher temp as they are usually used in the summer rather than the winter like cars. A marine battert holds less of a charge than a car battery of equal number. I take my boat out in the winter and push sheets of ice around and catch fish, but I am the exception. I have never had trouble with batteries except for trolling motor batteries. Maybe your connections are not good from the extra problems with corrosion.

[Duane HTP]

Your truck starts out of gear, turning just the motor and maybe a torque converter. The Boat starter turns the motor, the flywheel, the pump shaft which has the packing drag on it, and it has to turn the impeller which is pumping water.
Thus more draw. Duane HTP

[DickDanger]

As far as I can tell all of the connections are good in the boat. I have had the alternator bench tested, new brushes, re-wired it, new belt, the works. But I notice that if I start a day out at a full charge, after running the boat all day, there is a slight drop (usually a volt or 2). Even the times that I am driving for 30-40 minutes. I have noticed that MANY other people have the same occurence. -DD Out

[cruser]

How do you measure the drop in voltage? What value do you measure?
I also know about Ohm and Kirchoff and such. Blown509Liberator is correct. Was educated in electronics along time ago. I don't think it has changed much(I hope).
If your battery is not getting fully recharged, there is a voltage drop between the alt and the battery or the battery is weak and won't accept a full charge.
Extra resistance in a connection or wiring, a faulty voltage regulator or alternator, or some other component in the charging circuit will cause the voltage at the battery to drop.
A while back I installed one of those battery isolators in my boat when I added a second battery. The diodes in the thing prevented the batteries from fully charging and, I believe, shortened the lifetime of my batteries. I no longer use that type isolator.
I also increased the size of the wiring in my charging circuit. I use an ameter so the charging circuit has a pretty long run and the wiring wasn't up to supplying 2 batteries from a 100amp alternator. The new wiring allows the full output of the alternator to charge the batteries very quickly. I don't have any problem with losing voltage after a day of use.
cruzer

[bordsmnj]

in very basic elctronic(purely resistive)cicuits ohms law and jerkoffs law work just as stated.But when you have impedence(resistence) in the form of capacitive reactance(spark plugs) ,inductive reactance(through the generator/altenator and wire) and resistance(also across wires and gauges and such) they don't add linearly.in other words if you took all the readings and used simple math and theory and actual numbers would very a little and sometimes alot. for the complicated stuff trtigonomitry(math-yes spelling -no)is used when applying those "laws". So, anyway, try the bigger wire thing it helps alot. next time your in your boat when the motors been running a while feel the wire that feeds your battery. do it in a place if possible that the wire's temp is not affected by outside sources. for instance at a place that is not in dirrect sun light, is away from the headers, block and other big heat generators,etc that wire should be the same temp as the air. if it's warm or hot to the touch it's definantly too small. also go with finely stranded wire. the tinier the strands the better it conducts current. I don't now to much about motors but electricity is a friend of mine. sorry this is so long winded. i'm out.
[ September 06, 2002, 01:58 AM: Message edited by: bordsmnj ]

[greg shoemaker]

DD Do you have a stereo with a large amp ?

[hoolign]

I have a question somewhat along the same line as dick,why,after only an hour when i shut the boat down and go to re start,it always seems the starter is dragging,if i let it sit for an hour or so no problem,starts just as if it was a cold motor,it happened in my last three boats,460 bottom mount with headers,468 bottom mount with headers,and with a 460 top mount with logs,the voltage always seems to stay around 14v,the only real draw on this 460 top mount is the bilge pump,it'll drop 3 volts when i kick it in,im running 2 batteries with an isolator,but ..in all the vehicles ive run with headers no problem,and youd think the starters would get hotter with the headers being closer than in a boat

[DickDanger]

Actually, right now, I am just running a head unit with a built in amp, and a set of 2 way Eclipses, but I rarely even turn it on due to I cant hear it with the motor running anyways!!!! Greg, I think that I am gonna have ya do some work for me this winter if ya arent too busy. I need the pump yanked and powdercoated (dont wnat it chromed), and want to see what we can do to find some more hidden ponies in the mill. L8..-DD Out
P.S. Greg, you are more than welcome to come to our Summer Blowout at Pyramid if you arent busy, although if you DID show up, I can imagine that you would get nothing but tech questions all day. Let me know, and I will tell the guys to ease up on the questions. The thread is over on Hot Boats West

[HOSS]

Loose belt will have same effect. Run hicg amp alternator. I also run welding leads as my battery cables.

[greg shoemaker]

DD keep me informed. Hot Boat test 15 thru the 18 of Sept. I'll be busy at that time Greg

[Havasu Hangin']

DickDanger:
...But I notice that if I start a day out at a full charge, after running the boat all day, there is a slight drop (usually a volt or 2).The wire to your dash is longer than a car (and the ground). Length = resistance.
Longer battery cables = resistance.
alt heat = resistance
All of this works against what Mr. Wizard (AKA-Blown509Liberator) pointed out. Things heat up in a boat. Also, most marine alts put out 45-55 amps at around 3,000 RPMs, while most automotive alt put out a higher current at less RPMs (more electrical draws on a car).
I agree with bordsmnj and Hoss, to keep a good charge, you need the beefiest, shortest wires. Minimum 2 gauge for the batteries, and 4 gauge off a 100 amp alt. I just ran 8 gauge to my dash.
Like cruser pointed out, get rid of the ampmeter, if you got one.
hoolign- sounds like timing and compression...how much initial timing are you running?
And like Greg pointed out...get a bigger stereo... http://www.planetsmilies.com/smilies/happy/happy34.gif
[ September 07, 2002, 10:38 PM: Message edited by: Havasu Hangin' ]