86 Saltare keep blowing main breaker Coil is always SUPER HOT

[premierproperties]

Ive been chasing an ignition issue over the last several years. Ive replaced multiple coils, ballast resistor, 40a breaker, and recently my ignition module went bad. Boat runs good, but the breaker will pop 5/6 times each time I use the boat and the coil is always really hot to the touch. Any idea where to start?
Thanks!

[chris young]

Sounds to me like the alternator is putting out too much voltage, have you measured it? 40A is a serious amount of current. (burn your boat down serious) If you have to reset that breaker ever, you have a problem, if you have to reset it often, you have a big problem. Once the boat is running, (assuming it's wired the same as mine, and we're talking about the same breaker) the only current going through that breaker is what is charging the battery. If the breaker is popping and the coil is really hot, then the only thing that I can see to be at fault is the alternator. I seriously would not take that boat out on the water until you sort this out.

[lively]

wow ! the alternator should be internally regulated , and usually 50 -80 amps depending on the alternator 1100- 4300 rpm range is a median to look for ... the breaker is there simply for that reason you will need a meter and a amp clamp or a meter that will read amperage, and as for the coil 12v at ballast resistor , 8v at coil . temp 120 -130 normal operation temp and make sure the coil says externally resisted "aka ballast resistor"

[cadunkle]

Which breaker are we talking about? The 40A main on the dash or the 40A (50A I thought?) on the harness at rear of engine?

I had an issue popping the main in the dash mainly with radio turned too loud but occasionally other times. Replacing with a new breaker fixed it, the old one looked a bit worse for wear and I believe was popping early. Alternator charge current to batteries should not be going through the dash breaker, only the breaker on the engine. 40A sounds a bit light for that breaker as I believe the factory alternators were somewhere in the 45-52 amp range. I want to say I had a 51 amp Prestolite on mine before I swapped it out for a 105 amp 10si using a new 4 gauge charge cable.

[chris young]

Be careful trying to read current. The meter must be a clamp on type for anything over 10A. Multimeters are fused and will measure usually a max of 10A If you want to measure big current without a clamp on meter, then you need a shunt in series with the load, and then you measure the voltage across the shunt and convert that to current. You can buy one for about 30 bucks. http://www.digikey.ca/product-search/en?KeyWords=3020-01096-0&WT.z_header=search_go

That being said, you most likely do not need to be measuring current to find your problem. Measure the voltages like lively posted, that should tell the story. I really can't think of anything other than the alternator that could be causing your problem. If that breaker is new,and properly sized, and it's tripping, it's doing its job and protecting the boat. If you keep resetting it, you're asking for trouble. Air Canada burned down a DC9 because the flight crew kept resetting the breaker for a lav flush pump. And airliners are built to much safer standards than Supras are.

[premierproperties]

When I replaced the breaker, It was originally a 50a, however I couldn't find a 50 anywhere so It was replaced with a 40a. The Alternator was replaced 3 seasons ago with a 105amp. Prior to this season the breaker never tripped (from what I recall).
One other odd thing to note when I had the boat out earlier this week, while at Idle, my tach will randomly jump all over the board. When I idle the motor up it returns to normal operation
https://www.youtube.com/watch?v=jlHSvKFZIvc[/I]
Im thinking that my Alternator is the issue....

[lively]

tach pulse is from distributor, check you voltage .. or depending on what distributor you have could be ign module ... i just replaced my alternator from DB electrical .. i haven't tested it yet but states 105 amp @ 4200 rpm and cost was 57$ shipped to my door

[premierproperties]

The alternator was from DB electrical and I just replaced the ignition module last weekend...it's a Mallory distributor. I've got the boat by a friends whom is an electrician, gonna test the voltage today.

[cadunkle]

Since you say you replaced a 50 amp I'll assume this is the large breaker on the engine. What gauge wire are you using for your charge cable off the alternator and how is it wired up? If you are using the factory charge cable (10 gauge maybe?) that circuit breaker is protecting you from starting a fire. You can't put 105 amps down a tiny wire like that without melting it, and certainly a 40 amp breaker will pop with a load up to 105 amps. 40 amps would not be adequate even for the stock 51 amp alternator.

[flipz96]

The tach jumping like that is usually from the distributor.

[premierproperties]

i ordered a proper 50amp breaker. I tested the alternator and its producing 10-55 amps, nothing more. What gauge wire should be coming off the alternator?

[cadunkle]

How did you test max alternator output? You said previously that you have a 105 amp alternator.

50 amp breaker will trip with a 55 amp load. Size the breaker for the wire, not the load. Size the wire for the load.

[chris young]

http://www.engineeringtoolbox.com/wire-gauges-d_419.html

Engineering toolbox is one of my go to sites. You are looking at a minimum of 4 AWG for that kind of load. Remember, boat fires are very bad, erring on the side of caution is always advisable. How did you test the alternator? Did you test the voltages.