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Alternator Isolator or something else?? https://www.smwebhead.com/phpBB3/viewtopic.php?f=11&t=15361	Page 1 of 1

Author:	jpeloian [ Sat Mar 25, 2017 7:32 pm ]
Post subject:	Alternator Isolator or something else??
hi all.I have 2000 268 vista with a 5.7 VP. I am having a charging issue. I hadn't used the boat since October, got it running with a jump pack today. But while out running it would bog down when i would trim. Just a quick hit of the trim switch would cause it to almost stall. Went back to dock and took voltage readings at batteries. I had 12.5V at idle on both batteries. Hit the trim switch and it would drop to 10.xV if i held the trim engine stalled and would not restart unless i put the battery switch to both. I would expect the alternator to put out between 13-14V, but dosnt some of that get lost in the isolator? Is one battery charging and the other not even though i get the same voltage on both or is the alternator just not putting out enough? Any help would be greatly appreciated.

Author:	LouC [ Sat Mar 25, 2017 8:00 pm ]
Post subject:	Re: Alternator Isolator or something else??
I've never used an isolator but I can tell you with a new alternator on my old engine (but clean marine quality cables and terminals) I get 14.2 V at idle for either battery. So you may have a weak alt, or corrosion in your starter, starter to alt, and battery ground cable terminals. I'd start with cleaning all the connections and terminals, including the ground terminals on the bell housing of the engine (behind the exhaust hoses on each side). While the trim pump pulls a lot of amps, the system should be able to handle it if your alt is putting out enough amps and you don't have high resistance in the circuits.

Author:	chris268 [ Sun Mar 26, 2017 12:57 am ]
Post subject:	Re: Alternator Isolator or something else??
If my memory serves me correctly, the isolator will drop about .6-.7 volts through it Should be able to get a reading from, I believe the center post on your isolator and compare.... it it's dying with the trim load, either the battery is dead and won't hold a charge, or the alternator is not charging it.... imo

Author:	LouC [ Sun Mar 26, 2017 9:16 am ]
Post subject:	Re: Alternator Isolator or something else??
Also check the connectors at the trim relays. If the terminals are corroded it will cause it to draw more amps and drop your system voltage to the point where you can feel the engine stumble. I had this problem with my boat years ago with the old junk battery cable. After I replaced all the cables and put in a dual battery system (like 10 years ago) I never had that issue again.

Author:	jpeloian [ Sun Mar 26, 2017 2:19 pm ]
Post subject:	Re: Alternator Isolator or something else??
Thanks for the replies. im leaning towards the alternator,but want to cover all possible options. i need to check voltage at the alternator next, it may just be weak from age, it is 17 yrs old. Anyone have any recommendations for an aftermarket replacement? VP is too outrageously priced.

Author:	LouC [ Sun Mar 26, 2017 3:36 pm ]
Post subject:	Re: Alternator Isolator or something else??
Arco Marine is good ...

Author:	weather [ Mon Mar 27, 2017 5:42 am ]
Post subject:	Re: Alternator Isolator or something else??
As mentioned above - a passive isolator will drop your voltage at least .7V, the one in my boat dropped about 1.1V. One way to avoid this is to use the sense wire (a connection on the alternator). My boat had the sense wire (usually orange I believe) directly jumped to the output of the alternator. You could instead connect this wire to the battery side of the isolator, so the alternator would put out 14.x V at the battery, and around 15V at the alternator. I've had bad batteries 'pull down' the output of the alternator as well (I don't know how it does this, but it can). I always start by having the batteries load tested, it's easy and they are often the culprit. With the isolator, I would expect to see around 13.6V at the batteries with the engines running.

Author:	Surface Interval [ Mon Mar 27, 2017 12:55 pm ]
Post subject:	Re: Alternator Isolator or something else??
Before you go buying parts, have a look at the 70 amp Alternator Circuit Breaker between the trim tab pump and the battery charger and above the Isolator on the front wall of the engine compartment to see if it is popped. Mine popped once a couple years ago, but not since. I ran it that day for maybe an hour before stopping for lunch. Had to switch to both batteries to get it started. After a while, and when I was able to access the engine comp't, I noticed the breaker was popped. I reset it and everything was back on line and fine. Fully charged batteries should be 12.7 volts. The alternator should be producing somewhere around 13.9 to 14.7 volts. You should have about a half volt drop across the isolator. If you ran it a little while without the alternator a reading of 12.5 volts may be expected with the alternator off line. The voltmeter on the helm is not always very accurate due to length and size of wiring, less than perfect connections, etc. You may have caused the breaker to pop due to jumping it.................... If the Circuit Breaker is not popped and the alternator does not produce power, it might be a bad alternator. The alternator should have a smaller diameter field wire and a larger diameter output wire. Use a voltmeter to check the output terminal for 13.9 - 14.7 volts. If output terminal reads less or zero, verify that you have some voltage in the field wire. It's been a while, so I don't have exact numbers. You should be able to find better troubleshooting info on line.

Author:	Surface Interval [ Mon Mar 27, 2017 12:55 pm ]
Post subject:	Re: Alternator Isolator or something else??
Sorry for the duplicate post.

Author:	jpeloian [ Mon Mar 27, 2017 6:49 pm ]
Post subject:	Re: Alternator Isolator or something else??
Thanks Surface.. It looks like that breaker might be bad. I push it in and it dosnt reset. So that might be the culprit. The front of the isolater looks pretty well corroded but all the terminals are clean, not sure it that matters or is just cosmetic. The other thing i noticed, and is most likely not related is that my Guest on board charger is not functioning. No LEDs lit and no voltage/charge going to the batteries. I do have power to the charger though. So that might have just been a coincidence that it failed same time as this other issue. Thanks again for all your help.

Author:	Surface Interval [ Mon Mar 27, 2017 8:14 pm ]
Post subject:	Re: Alternator Isolator or something else??
Check the circuit breaker for continuity. The Guest chargers have been a known problem. One or both sides have failed on several boats.

Author:	signalstan [ Tue Mar 28, 2017 6:55 pm ]
Post subject:	Re: Alternator Isolator or something else??
I had a similar problem it was loose ground wires on back of starboard engine

Author:	jpeloian [ Sun Apr 02, 2017 7:37 pm ]
Post subject:	Re: Alternator Isolator or something else??
Thanks everyone for all your help. I spent the better part of the weekend trying to get this going. I replaced my charger and got a good charge on both batteries. It turned over and fired right up. Checked voltage coming out of alternator and it was 14.2V all good or so i thought. Was idling fine and i had fully charged batteries, hit the trim switch and voltage just dropped. From 13V to 11V. Shut it down and check batteries, both showed 12.8V. Tried to start it but nothing no chirps nothing complete dead, as if no power at all. Checked all the fuses, they were OK. Tried again and it fired right up. Really confused now. Shut it down and no start again.But had my trusty 11 year old daughter to help me find the problem . She asked to try and start it. She turns the key and i hear click click. Hey do that again.. Relay... There are two of them in front of the throttle body the one on the left was clicking. wiggle it and it fires right up. Look at voltage gauge and it barley reads 12V, wiggle it some more and it jumps up to 13V. Take it out and check the wiring underneath. They look burnt and in bad shape, the holder/plug that the relays go into is melted as well. Time to replace it.. Only problem, when looking at the VP web site that part is no longer available. Obsolete parts.. Bracket, Relay 3852210 Terminal 3852247 Terminal 3852246 Any thoughts on what to do? Yeah i could cut the wires and put new ends on them and plug the relays directly into it but that dosnt seem to safe, too high of a chance for a short, especially right in front of the throttle body . What say the collective brain trust?

Author:	LouC [ Mon Apr 03, 2017 3:20 am ]
Post subject:	Re: Alternator Isolator or something else??
Go take a look at the Painless Wiring website. They sell relay holders and relay wiring harnesses which you could adapt if these are standard Bosch style relays. I've used them for off road wiring harnesses for the Jeeps. Good stuff. Google Bosch relay holder that might be the part you need. I think I found some on Amazon

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