Battery question
 

Any problems with using 2 deep cycle batterys in a boat???
instead of cranking marine batterys???

Why would you want to?

Deep cycle batteries are made to discharge small to medium amounts of current over a period of time and can be drawn down. Cranking batteries are made to discharge large amounts of current over brief periods of time and are sensitive to significant discharge (it ruins them)

A DC may not crank your engine- especially if you've run them down a bit and your engines are hot/run alot of timing.

Tell us what you want to accomplish and maybe we can suggest something.

I have then in the boat now,and both of my alternators failed,they burned the studs on the back off,I thought the deep cycle battery might be the cause
also when I start/crank the port motor the radio goes off and turns back on about 5 seconds after engine starts,I dont know if thats normal or not

You have wiring problems. Quite possibly with your grounds.

The alternators don't know what batteries you have in there- they just ouput current. DC's don't take more than a regular battery to charge, but they don't live as long if you blast them instead of trickle charging them, but that's a different issue.

I thought the same,did a voltage drop test on the ground side,with the engines running ,from the battery ground to the back of the bellhoushings stud I have .045mv
I also did a voltage drop on the positive side,with the engines
running from the alternator stud to the battery positive I have .160mv all seems fine there.
Now the other thing I also had was only 1 Perco battery shut off switch and always ran the boat with the switch on the ALL
position,I was told thats a No No,
I installed a second switch now so I could keep the alternators and batterys separate,
I thought maybe the alternators were fighting each other to charge the batterys

The alternators can't tell that each other are in the system. They sense voltage and switch to charge mode when necessary.

Meter tests are often inaccurate or inconclusive- you have to duplicate the load to see what's really going on. I've seen connections that had low impedance with a meter that were 90% corroded. It doesn't take much current to run an ohmmeter. One single strand of wire will show very low impedance, but you can't run a 70 amp alternator through it. I'd pull all the grounds and reseal them, replacing the star washers. I'd also pull the alternators and clean everthing up really good.

I have ran two "dual purpose" batteries for the last two seasons and they have worked well. And I run my stereo a lot while sitting.

I know what you mean about the single strand,
the readings above where from a voltage drop test.
Tonight I ran a 8 gauge ground wire from the back of the block to a bus bar behind the dash panel and ran the grounds to it,that took care of my gauge issues,lights and gauge readings dont bounce when I trim up or turn the nav lights on,also tachs now seem to work fine.
Now my radio still goes out when I crank the port motor and when I use the trim tabs,I checked the voltage at the radio circuit breaker,it drops down to 9.5 volts during cranking or trim use.
I was thinking of doing the same with a power wire ,running a 8 gauge wire to a bus bar behind the dash,
I believe that the correct way of doing it,
where would you get the power supply from??and would you tap into the ignition switch??

Your systems legs should come right off the battery switch and have fusible links in them. One goes to the tabs/drives supply, one for dash/engine circuits and one for cabin circuits. Obviously this is for a basic performance boat. If you have electric fuel pumps that draw big current, another circuit is waranted. Big stereo? Another one. BIG stereo- separate battery.

Make sure your bilge pump circuit comes off of the feed side (input) of your battery cutoffs.

Your boat sounds just like cbgnrl's '97 290 PQ. I tease him all the time it was wired by monkeys. PQ makes a nice boat but their wiring left a lot to be desired. He is constantly chasing electrical gremlins.

Same Boat
hopefully this will take care of it.

thats kind of what I was thinking.
Chris thanks for taking the time to respond.

Part of the problem, at least with the cbgnrl's PQ, was the power for some of the heavy draw systems was not coming off separate legs from the batteries.

I ran a 8 gauge ground wire to a bus bar behind the switch pael last night,
I will tonight run a 8 gauge power supply wire to a bus bar behind the switch panel also and tap into it.
that should take care of it.I hope!!!

Ran the 8 gauge power wire to a bus bar behind the switch panel and connected the radio,trim tabs and trim switches to it,everything now seems to be working fine,gauges dont jump up when I turn on the nav lights or any other accesory,radio also works fine while I use the trim tabs,seems to be all good at this time.
the only issue I still have is the radio going out during engine cranking,I never really paid attention to it before,I think that would be normal operation,Iam I correct ?????

Optima Blue tops are another option, There more money but a great battery for marine use

Run a search on here about Optimas. My experience was bad, as has been many others. Keep in mind, I buy them by the pallet for our fleet and I've had stellar service life from them in our trucks. The boat is a different story.

I buy the basic battery & replace them every spring.

You are are right about Powerquest Wiring, I laughed at a few of the connections / wiring. I did the same thing, ran heavier wire and took care of a lot of problems. As far as batteries, I run 2-6 volt batteries and one big diesel start for cranking the engines. I just spend 4 nights on the Mississippi river on an island with the refrigerator running and the radio, and my 6 volts never went dead.

My 2000 F260SS Formula came new with 2 deep cycle batteries. Replaced one last spring & the second one this spring. I think 7 & 8 years on a battery is pretty darn good. I stuck with the same.

A deep cycle will spin a low compression small block just fine. The bigger you go, the worse they work.

Maybe check where the radio is picking up (+) power from. It may be a circuit that is temporarily disabled when cranking.

I think that is normal as all of my boats have done this.

after installing 2 bus bars,1 ground and 1 power,and 8 gauge wires,I took the boat out for a ride,all seem to be working fine and all gauge reading are now good with out any voltage drops/spikes.
Now why didn't the factory do it that way,how much could they have really saved.:rolleyes:

Absolutely true. A brand new Interstate 27 DC would not spin my 502 .

If they did, they'd have to raise the price by $8,000.

Seriously- most boat manufacturers spend their money on what you can see and figure it'll not be their problem by the time your half-assed rigging takes a dump. Blame it on the consumer than demands flash over quality.