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Charging System Not Charging

donnella

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" 1978 MerCruiser 470 4 cylind

" 1978 MerCruiser 470 4 cylinder

We were on the water the other day and our tach started jumping all over the place then the motor cut out 3 or 4 times. It finally quit and when we tried to start it, the engine wouldn't even turn over. We waited a few seconds then it started fine but we had to limp it home at low speed. Also, whenever we went ovrsomeone else's wake, our gauges jumped around and the fuel gauge dropped all the way to Empty. Once the boat levelled out, they were fine (the tach was still jumping some but not as bad at low speed and the guages have never done this before).

We checked our boat's charging system and it doens't seem to be charging. We checked the battery and the volts run in the low 12's running and mid 11's when it's shut off.

We thought it might be our rectifier but we were told that they don't make rectifiers for this year boat anymore? We're also wondering what voltage test we can do on the rectifier, voltage regulator and stator so we can determine which one is bad? Our voltage regualator was changed 3 years ago; would it go bad this quickly?
On a similiar note: When we first used the boat this year it wouldn't start (no spark). We traced everything and ended up replacing our cellenoid, coil, points and condenser (they all tested bad), plugs, roter and distributor cap. It ran fine last year when we put it away. What could have burned the low end electrical equipment? It's an old boat and we thought it was just bad luck that it all went out at once, but now we're wondering.

Any help would be greatly appreciated! :) We're in the process of getting a manual for this boat but we don't have it yet (we've only had the boat a year and have absolutely no problems until now). "
 
Disconnect the tachometer wir

Disconnect the tachometer wire (grey) from the negative side of the coil. If that doesnt work try changing the battery (Battery could be sulfated if it has been sitting longer than 30 days without getting a charge.
Dania Marine 1-800-748-7739

Gabriel
 
" Sounds like a bad electrical

" Sounds like a bad electrical connection somewhere between the battery and the engine. Since the voltage is higher when engine is running, your charging system is working, at least partially -- charging voltage should be about 13.8 volts. Check for loose or corroded battery connections, loose or corroded connections at the engine end of the battery wires. Check that the wires themselves are in good shape along entire length. "
 
" Thanks for the advice guys;

" Thanks for the advice guys; it really helped. We double checked our battery and it was dying. We bought a new Deep Cycle/RV battery and tightened all the connections but we have another question: Our battery reads 12.6 to 12.7 when not running and 12.63 when running. When boat is first started, volts drop to 12.5 but charge right up to 12.63. We read that boat batteries are supposed to be at 13.8; is this true for all batteries? Do we possibly have another problem or is our battery fine?

Thanks again for the all the help; we really appreciate it! "
 
Is the battery fully charged?

Is the battery fully charged? You should make sure the battery is at full charge before evaluating the alternator and regulator. The best is to evaluate the alternator using an appropriate tester. As an alternative charge the battery with an appropriately sized AC line charger for 24 hours before running the alternator voltage testing.

12.63 volts is not high enough to bring either a starting or a deep cycle battery to full charge. 13.8 is a safe compromise between rapid charging rate and battery life for the intermittent charging you get during use of a pleasure boat. I don't think you will be satisfied over the long term with the current voltage setting of your regulator especially if you use the battery for house lights and refrigeration when on anchor. Your battery capacity will not be up to snuff and your battery will recover slowly with the engine running.

Some regulators have voltage adjustments. Otherwise you will need to replace the current unit with one factory adjusted to a higher voltage. The battery manufacturer should be able to give you specs on what charge voltage is best for you particular battery.

Good luck!
 
" Thanks again Bilgeguy. Yes,

" Thanks again Bilgeguy. Yes, our battery was fully charged and we changed our battery cables today but our battery still reads the same; it's not charging when it's running so we've narrowed the problem down to the voltage regulator or alternator. We tried to adjust the regulator but got nothing different on the multimeter. My next question: What is the specifics for each test (with a multimeter) to check the regultor and alternator? We suspect our regulator but we want to test both units so we're not replacing parts unessarily. A side note: our voltage regulator was changed 3 years ago.

Any more help would be greatly appreciated! Thanks again guys! :) "
 
" Donnella, Sorry I am not qu

" Donnella, Sorry I am not qualified to give you a step by step formula for testing your regulator and alternator. You could refer to one of the books on marine electrical such as Nigel Calder's "Boatowner's Mechanical & Electrical Manual: How to Maintain, Repair, and Improve Your Boat's Essential Systems" which gives step by step test methods. From your description, I think your alternator is the more likely culprit. You might want to remove the alternator and take it to a shop for evaluation and possible repair. "
 
The best thing to do is repla

The best thing to do is replace the alternator and regulator with a marine 1 wire alternator. ( The fewer parts you have the better )
Jay
 
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