470 smokes alternator belt and kills engine

I have a 105 amp 1 wire alternator on my 470 and the engine runs great with the alternator disconnected or the belt loose. As soon as I connect the alternator or tighten the belt it starts loading the alternator and the belt smokes from the load and it will kill the engine. I put an amp clamp on the alternator wire and am at 20 amps when the engine dies. This has the pertronix ignitor installed in place of points and when I turn the key to the run position the pertronix is drawing 9 amps which seems high to me. I have checked all of my grounds and all are making good contact.

a high output alt need 2 belts to function properly and all you need is a 55A alt to run the boat
You may also have battery issues to draw that much

Bt Doctur said:

a high output alt need 2 belts to function properly and all you need is a 55A alt to run the boat
You may also have battery issues to draw that much

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The alternator only comes with a single pulley and I see people have added them to the 470 on a regular basis with no issues. If I put a 3/8" belt on it (which is the pulley size on the alternator) it will slip and smoke. If I put a 1/2" belt on it, it will smoke but keep its grip and kill it. Again I'm only getting 20 amps at the alternator wire which in my mind is not enough of a load to pull the alternator that much. As soon as I loosen the belt or remove the wire from the alternator it runs like a top!

You probably already killed that alternator with what you're doing. Just put a regular 55A alt on there and be done. Unless you're running a full size refrigerator, plus air conditioning, a toaster and the stereo all at the same time, you just don't need it.

o2batsea said:

You probably already killed that alternator with what you're doing. Just put a regular 55A alt on there and be done. Unless you're running a full size refrigerator, plus air conditioning, a toaster and the stereo all at the same time, you just don't need it.

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So this is what I did tonight. if I run the alternator wire and ground to a separate stand alone battery it charges at 14.5 volts just like it should. As soon as I hook it back up to the engine battery it loads up the alternator and smokes the belt.

swap your battery with the standalone battery and report back
Or you output wire is somehow grounding out and once connected the amps go directly to ground overloading it

I ran the alternator charge and ground wire to a stand alone battery last night and it charged it at 14.5 volts and never got hot, smoked the belt or pulled the motor down!
Its gotta be something on the engine grounding out. The only thing not factory is the pertronix electronic ignition. From what I can find online those units are either good or bad so not sure how it could be shorting out.

Other than briefly with a discharged battery, the alternator should not be putting out that much current running just the engine. SOMETHING is drawing way too much current. I'd start by switching off all circuits on the boat or pulling the fuses, one by one to eliminate any off engine draw. If you eliminate an off engine high current draw, the next thing is what on the engine is drawing that kind of current. There are only 4 or 5 objects on the engine that use electricity: Starter, external starter solenoid?, electric choke?, ignition system, ignition coil. At 20 amps draw, that would be 240 watts of power draw. At that power level, noticeable heat will be generated. For example a medium power soldering iron only draws 50 watts. A short to ground or a load of 6 to 7 ohms would account for the 20 amp draw. Given that your engine will draw electrical power while running, you are likely looking for a load or "short" of 10 to 15 ohms.

Happy (careful) hunting.

PS... I don't know what your expertise level is so I'm sorry if I'm talking down to you, but you cannot measure ohms on a powered circuit. So when checking for ohms, make sure the battery is disconnected.

Thanks for the information. I would have thought with that kind of draw I would have a wire melted down somewhere but nothing is getting hot except for the alternator and belt when it is slipping. The only high amp draw I have is at the pertronix ignition red wire and it is 9 amps. When I disconnect that the whole system is drawing about .1 amps. I called Pertronix and they tell me that can be a normal amp draw for that unit. I have a brand new mercruiser internal resistor coil and have removed my resistor wire and ran a new power wire from the choke (where the old resistor wire got its power) to the coil and it also has the start circuit wire from the slave solenoid to provide 12 volts when starting.

Double check the wire from the alt output to the main post at the starter

Bt Doctur said:

Double check the wire from the alt output to the main post at the starter

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I have already added a new 8 gauge wire and new eyelet ends.

Your not making any sense. Hooked up to a standalone battery the alt works perfectly, hooked to you engine wiring it dosent. Try swapping the batteries. If it still has problems your wiring is suspect. Remove the 8 gauge and run a 14 ga from the alt to the battery and retest
NOT TO THE STARTERS BATTERY POST, TO THE BATTERY DIRECT
If the alt performs normally you have a wiring problem with the 8 Ga

Bt Doctur said:

Your not making any sense. Hooked up to a standalone battery the alt works perfectly, hooked to you engine wiring it dosent. Try swapping the batteries. If it still has problems your wiring is suspect. Remove the 8 gauge and run a 14 ga from the alt to the battery and retest
NOT TO THE STARTERS BATTERY POST, TO THE BATTERY DIRECT
If the alt performs normally you have a wiring problem with the 8 Ga

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What do you mean I'm not making any sense? I can hook up the alternator positive and negative wire to a separate stand alone battery that is not connected to the boat engine wiring and start the engine with the battery that the boat normally runs on that the alternator is normally connected to. When I do that the alternator functions perfectly and charges the stand alone battery at 14.5 volts. If I take the same alternator wire and connect it to the boat battery within a minute the alternator starts to load up and smokes the belt and it does not put out any more than battery voltage and draws 20 amps. I have swapped the batteries with the same results.The alternator originally had a 10 gauge wire on it but according to a wiring chart I found it was supposed to be 8 gauge so I changed it. Because of the results of the remote battery in my mind it has to be something in the boat wiring and I am looking for suggestions as to what that may be.

If I take the same alternator wire and connect it to the boat battery within a minute the alternator starts to load up

It does not "load up" on a remote battery so you proved the alt is functioning but hooked up to the boat system it does not.I dont know where your connected to the battery . Most times its at the starters main battery post. I suggested removing that 8 ga and using a 14 ga directly to the batteries pos post.
One of 2 things will happen. The alt will work perfectly or you will smoke the wire. Connected directly at the battery would indicate a bad battery drawing excessive current not so much the "load" on the system.
Another test is to see if you have battery voltage at the wire that connects to the alt. You should see battery voltage or your wiring is suspect

When I bought the boat this spring it had a 10 gauge wire hooked directly from the alternator to the positive post of the battery and it was loaded down and smoking from the start (I know, don't buy a boat without test driving it first right)! I connected the alternator wire to the solenoid post so it would charge both batteries when switched to "all" which from what understand it quite common to do. Just a little background on myself. I have been turning wrenches for 30 years, I'm a Briggs & Stratton Master Service Tech and a Kohler Expert Technician (I know, that and a dollar will buy me a pack of gum!) so I have a fairly good idea of what I'm looking at but I am as baffled as can be by what is going on! Thanks for your input!

Do you have 2 batteries in the boat and do you have the selector switch on "Both"
AND are the batteries connected correctly.Don`t be offended, it`s been done before

Re: "..so it would charge both batteries when switched to "all" which from what understand it quite common to doe:"..."

Yes, it is quite common. I work in a big box marine store summers, and I will tell you that folks who do this on a regular basis are good business for us. They usually get only 2-3 ish seasons on their batteries. There are only TWO situations wherein one should have the battery switch on BOTH ( or ALL)...

1) Boat won't start on battery 1 or battery 2, and your last gasp try to start is "BOTH"
2) Engine is running on one battery and you want to switch batteries, usually to charge an almost dead battery, i.e. running on battery 1 and you want to switch to battery 2, you switch from #1 to #2 transiting "Both". BEFORE you do this use a multimeter to make sure that the battery switch is "make before break" . To do this, with batteries disconnected ( not wired) connect the #1 switch terminal to the #2 switch terminal. Put battery switch in #1 position. Put ohmmeter on the battery switch common terminal and the other lead on the jumpered #1 and #2 terminal. Ohmmeter should read close to zero ohms. Briskly switch battery switch to position #2... Ohmmeter should not flicker. Analog meters are actually better for this test.

Why you shouldn't charge on "BOTH"... When you charge in#1or#2, the alternator makes sure that excessive current does not flow into the battery. When you put the switch in "BOTH", there is nothing to prevent current flow BETWEEN the two batteries, and unless both batteries are identical in age and construction and have always been run as BOTH, there will always be an uncontrolled current flow between the batteries. I get 6 to 7 seasons of battery life on my boat, where one battery starts the engine typically, and the other battery, a dual purpose, runs the bilge pump on my open cuddy cabin with a non self bailing cockpit and its electronics. Typically, I start and run on one of my batteries, and when return, I switch to the other.

.View attachment 21492

Note "Enhanced Fishability" install of Bimini.

I do have 2 batteries. At first I just ran the alternator wire to battery 1 but then realized that battery 2 would not charge if hooked up that way so I switched it to the solenoid so it would charge on either both or 1 or 2. It makes sense not to run them on both other than in an emergency situation but other than a portable battery charger how do you charge battery 2 if the alternator is not connected to the solenoid and just to battery 1? BTW it had the alternator issue all along when it was hooked to battery 1 only.

You put the feed to the starters main post when the battery cable goes. Even number days use #2, odd number days use #1.
Other then that, a battery isolator system or a Blue Sea type

Bt Doctur said:

You put the feed to the starters main post when the battery cable goes. Even number days use #2, odd number days use #1.
Other then that, a battery isolator system or a Blue Sea type

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That's where I had it. It is back on the #1 battery now. Results are the same either way, loads alternator and belt smokes. I can disconnect alternator wire from battery and start engine and runs great. As soon as i just touch alternator wire to positive post engine bogs down and belt starts to smoke.

I can disconnect alternator wire from battery and start engine and runs great. As soon as i just touch alternator wire to positive post engine bogs down and belt starts to smoke.

what happens when you put the wire to battery 2 ? This assumes you have the neg terminals connected together
Have you switched the onboard battery with the remote one you used to test with?
If it works correctly on a stand alone battery it should work correctly with the boats battery.
Is almost as if your connecting the alt output directly to ground

Bt Doctur said:

I can disconnect alternator wire from battery and start engine and runs great. As soon as i just touch alternator wire to positive post engine bogs down and belt starts to smoke.

what happens when you put the wire to battery 2 ? This assumes you have the neg terminals connected together
Have you switched the onboard battery with the remote one you used to test with?
If it works correctly on a stand alone battery it should work correctly with the boats battery.
Is almost as if your connecting the alt output directly to ground

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I've tried the other battery and it does the same thing. Yes you are correct it acts just as if I was grounding it!

try this, remove the alt wire and read the voltage on the wire, should be battery voltage.
Start the motor and read the alt output on the stud. Polarity of both tests should be the same.
Did this alt ever work correctly or is this a new unit never run?

Battery voltage at the wire. 34 volts dc at stud with no wire attached. I replaced the original alternator after our first time out because the belt was smoking and a bearing was loose. I replaced it with an identical alternator with the same results as the one with bad bearing. So thinking it was bad returned it for another identical replacement only to get the same results! Fun, right!!

there`s your problem ,single wire output is 14.6 .
34 volts dc at stud with no wire attached.
the alt is running wild because it cant sense the battery voltage

Had one wires on my old cruiser. Worked great and never caused me any trouble. The only knock on them is you have to 'boot' the gas once or twice to get them energized, and they can stop charging at long, no wake zone speeds.

Jeff

Bt Doctur said:

NSTALLATIONTo install a 1-wire alternator, disconnect the positive battery cable, unbolt and remove the original alternator, install the new Tuff Stuff 1-wire alternator and re-tension the drive belts. Then simply run one wire from the alternator ‘battery’ terminal to the positive termi-nal of the battery or to the starter solenoid main lug, which is con-nected to the positive battery post. Make sure that the battery is fully charged. Reconnect the positive battery cable, start the engine and using a VOM meter, verify that the alternator is charg-ing at least 13.8 volts @ 1,000 engine RPM’s.

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This is where is gets strange. It work perfectly on a remote battery, charges at 14.5 v all day long. The second I hook it to the battery with the boat wiring it loads the alternator. The other odd thing is if I try to isolate the Pertronix electronic ignition by disconnecting the power feed from the choke and slave solenoid and running a direct 12 v wire from either the boat battery or a remote battery it either runs horribly out of time or will not start at all. Pertronix says they're unit is either go or no go, but I wonder if it is shorting out somehow.

highly doubtful any electronic unit can pull down a 100 amp alt and timing is usually not changed by changing a voltage source. Double check the alt output again . Voltage should not be more than 14.6 Can you source another alt maybe even a 3 wire for testing

Bt Doctur said:

highly doubtful any electronic unit can pull down a 100 amp alt and timing is usually not changed by changing a voltage source. Double check the alt output again . Voltage should not be more than 14.6 Can you source another alt maybe even a 3 wire for testing

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Its definitely 34 volts. When I hook it up and it starts to smoke the belt it is pulling 20 amps at the alternator wire, which I wouldn't think that would be enough to draw it down. I wondered about a 3 wire alternator if it would make a difference with the separate signal wire. I dont have access to a spare on to try however.