Amp gage

Loyd Dinneen

Active Member
Jul 29, 2017
484
Las Vegas
Boat Info
1977 Sea ray 240 SDA cruiser w/ twin 470 mercs.
Engines
Twin 470 Mercruisers
I have a 77 240 SDA with twin 470's. The port engine amp gage seems to be pegged over and doesn't move at all when the engine is runnning. Checked the voltage output at the battery and it seems to be putting out power and increases as you increase rpms. Not to sure on what it is suppose to put out as it is one of those Mercruiser charging systems that uses some type of coolant cooled system not a alternator. The starboard engine gage works great.
 
I only measured the suspect engine and it was 12.3 volts at the battery and as the rpms went up the voltage increased. I had at one time checked the starboard engine and it was 12.5 volts. The gage is a amp gage. I am going to put in some volt gages to measure battery voltage.
 
Never jump start a dead or very weak battery, keep the connections clean and you should be ok. Some have replaced the bad regulators with Harley Davidson rectifier/regulator from the Big Twin fammily
 
I just checked the battery that I had my solar charger on an it put a full charge on the battery I wish I would of has the switch on both to see how it would of worked.I measured the voltage on the starboard battery and it is at 12.3 volts, a little low at 80 or 90 percent. I will put the solar charger on that one tomorrow and use both from now on.I will remember that about the harley parts. Is that the same setup that Mercruiser has on this 470 engine? 99% of the problems with batteries is because of dirty terminals, found that out when I was twisting wrenches. And you should only charge up a dead battery jumping it only draws the power from the other battery and leaves very little power to turn over the engine to start.
 
Last edited:
your charging system does not tolerate dead batteries being jump stated and being charged by the stator system. To remove the Amp gauge and install a volt gauge a slight wire modification is necessary.
The motorcycle and yours is basically the same a stator and rotating magnets
creata a sort of AC voltage. Its actually a square wave AC signature that outputs around 30volts AC into the regulator/rectifier.
 
I will be doing something with the gauges now I have another project and that is putting in a third battery to help with the house and an extra boost for the starting of the engines. I am going to buy a 4d battery to do this as it is less expensive than two batteries and have more crank amps and reserve. What I need to know is the easiest and safest way to wire it in. Was thinking of wiring the positive lead to the dual terminial on the perko switch for the starting side. Not sure how to get the house power into that. I know that when the perko switch is off I still have house power. Thanks for all the help and diagrams very helpful and will be entered in my notebook for the boat.
 

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