www.iFourWinns.com

My starting battery recently gave up on me and has since been replaced.

Upon installing the new battery I started watching the voltage meter on the dash more closely and see that it never gets to 13 volts.


I pulled out the multimeter and performed tests in the following locations with the engine at idle;

Alternator 14.5v
Isolator (centre) 14.3v
Isolator (bat 1) 13.3v
Isolator (bat 2) 13.4v
Switch (bat 1) 12.98v
Switch (bat 2) 13.2v
Dash meter (back side) 12.7v

I tried running a second #12 wire from the isolator to the bat 1 post on the switch and saw no gains.

I recognize that I should expect approx. a 0.6v drop across the isolator.

Am I being robbed of Voltage, and is the isolator suspect #1?

Any other thoughts to share?

Alex

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2004 - 288 Vista
Twin - 5.0 Volvo Penta GXi DP

I'm not familiar with an isolator and how it affects charging voltage but if what you listed seems to show quite a drop from the regulated voltage at the alternator to what the battery sees (through the isolator)?
I just put a new alternator in my old boat because the charging voltage was jumpy at certain rpms and the alt got sprayed with salt water when a cooling hose popped off 2 seasons ago. Voltage measured at the alt was 14.3 v and at the batts it was the same.
Does your alt use a sense "S" wire and if so, where does it sense voltage?
In my installation the S wire from the alt was connected in the ignition wiring under the dash. When I got the new alt from ARCO, the instructions said to measure voltage at the S wire with it disconnected from the alt. What I found was that it was more than 2 volts lower than the batt voltage. So the instructions said to not use that sense wire but to use a jumper between the S terminal and the alt output, which is connected directly to the battery. Before I made this change the dash gauge said 13.5-14V but the batteries were seeing 15.5V, too high. When I re-wired it they way the instructions advised, I got 13v on the dash gauge and 14.3 v at the batts. Not sure if this could be part of your problem. What gauge battery wiring do you have? How long are the cables?

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88 Four Winns 200 Horizon
4.3 OMC Cobra-4bbl
2002 Walker Bay 10/2012 Suzuki 2.5
2008 Walker Bay 8

1998 Jeep Grand Cherokee 4.0/Selectrac
2007 Jeep Grand Cherokee 5.7 Hemi/Quadradrive II

I don't believe my alternator uses a sensing wire, but I can't seem to locate the volvo wiring diagram for my engine to confirm 100%.

The alt connects direct to the centre post of the isolator. From there the current is isolated and sent to each battery post at the switch. From what I have read there is an expected loss of approx 0.6v from the isolator. I am seeing closer to 1 volt. What else confuses me comes next.... I get a voltage from the Bat 1 post on the isolator, this connects direct to the bat 1 post on the switch with what looks like a no.12 wire, and I see another loss... This wire is no more than 3' long. I tried adding a second no.12 wire to recover some lost voltage but got nothing.

I have no idea what is causing the loss between the alt or switch and the dash meter either.

Do you recall what gauge of wire you have from your alt to your battery?

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2004 - 288 Vista
Twin - 5.0 Volvo Penta GXi DP

I used to show less than 12 volts at my gauges before bypassing my isolator. I now show around 13.2 volts. The disadvantage is that I can't charge my house batteries while running the engines which is not a big deal to me since I have a generator to charge the house and I have several friends with generators should mine go down.

I've done some research on isolators and found that they are not that simple to install correctly, look at the following link for installation instructions on the different ways to connect a battery isolator depending on the model of alternator:

http://www.allbatterysalesandservice.co ... 80012Q.pdf

Four Winns electrical engineering can't even size wire correctly what faith do I have that they installed the isolator correctly?

It's interesting to note that the Group 2 alternators in the link show that the GM engine alternators require an isolator with an excitation post which mine did not have. While my engine is a GM block I am not sure that Volvo uses the same alternator as GM and I haven't found anything on the internet that tells me the manufacturer of my alternator. I haven't checked the alternator itself to see if there are markings that show the actual manufacturer.

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2004 Vista 298
Twin 5.7L Volvo Penta GXi-E

The wiring that connects the the battery to the alternator, is 10 gauge. It runs from the alt to the assist solenoid and then from that to the starter terminal. Then the current is taken to the common battery cable that goes to the switch (that cable is 2 gauge).
I would be surprised if a boat as new as yours does not have an alt with a sense terminal. Look on the back of the alt, how many terminals do you have? On mine there is the one big one which is the alt output, and 2 smaller ones labeled 'E' for excite and 'S' for sense.

http://www.arcomarine.com/xhtml/Pages%2 ... nators.pdf

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88 Four Winns 200 Horizon
4.3 OMC Cobra-4bbl
2002 Walker Bay 10/2012 Suzuki 2.5
2008 Walker Bay 8

1998 Jeep Grand Cherokee 4.0/Selectrac
2007 Jeep Grand Cherokee 5.7 Hemi/Quadradrive II

I see they recommend a No.8 wires from alt to isolator and isolator to batteries... I am going to start with that.

As for the Group 2, they specify this requirement starting in 2005 so I think you and I are ok.

Great link, thanks.

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2004 - 288 Vista
Twin - 5.0 Volvo Penta GXi DP

I'm going to have to take a closer look to figure out what I have for an alternator and report back.

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2004 - 288 Vista
Twin - 5.0 Volvo Penta GXi DP

to make it easier to look up get the Volvo part # for yours and look it up in the Arco catalog....

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88 Four Winns 200 Horizon
4.3 OMC Cobra-4bbl
2002 Walker Bay 10/2012 Suzuki 2.5
2008 Walker Bay 8

1998 Jeep Grand Cherokee 4.0/Selectrac
2007 Jeep Grand Cherokee 5.7 Hemi/Quadradrive II

Here is the procedure for testing a battery isolator:

Battery Isolator Testing
1. Remove all wire connections from the isolator.
2. Setup a digital multi-meter (DMM) in the diode test mode.
3. Connect the red probe from the DMM to the alternator input (A)
and the black probe from the DMM to the battery output terminal
to be tested. A good isolator connection will show a reading of
0.4 to 0.6VDC.
4. Connect the DMM black probe to the alternator input (A) and the
red probe to the battery output terminal to be tested. A good
isolator connection will show a reading of OL.
5. Repeat steps 3 and 4 for the other battery output terminals.

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2004 Vista 298
Twin 5.7L Volvo Penta GXi-E

^^This boat has turned your ass into a full on goddamn marine mechanic! I'm impressed!!

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V475
Chris Craft Catalina 23 w/ 300 G2
Previously-V338, 248 Vista, H210

Good call.... I will do this before spending time and money on wires.

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2004 - 288 Vista
Twin - 5.0 Volvo Penta GXi DP

Another reason to use a V.S.R. or a battery combiner. No voltage drop! Do remember, that the .6V is text book. So it could be a tenth higher or lower. More higher would be the norm.

I do know that ProMariner makes a isolator with zero V. drop.

As to the other drops, we all know that FW undersize there wires.

Stopped by the boat to test the isolator today and it tests perfect.

Wondering if the switch could be the culprit.

Also had a look at the alternator and saw a 3rd (purple) wire. Totally missed that last time I looked.

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2004 - 288 Vista
Twin - 5.0 Volvo Penta GXi DP

Your isolator will cause a voltage drop, nothing you can do about it it's just the way they are. You will spend a lot of time and effort to fix something you can't change.

If you want to have a proper battery isolator that will not have a voltage drop and you don't have to keep fussing with you will want to replace the isolator and battery switch with a power distribution cluster. Choose the one you need (single or twin engine) it's an easy install and your life will be much easier.

http://www.marinco.com/en/products/dist ... n-clusters

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2000 268 Vista "Reely Nauti"
http://www.facebook.com/#!/rivercruiser

I would not go that far, and for give me. That goes back to a V.S.R. or combiner. In this case, add one V.S.R. (or combiner) and a new battery switch. Also check your cables!! I forgot to mention, depending on the year, FW did not use tinned/marine grade wire.