1978 Mercruiser 228 Alternator Question

[THenning]

Hi All,

I have a 1978 Mercruiser 228 inside a Webbcraft 18V.

Last night, I was out on the lake and I would lose power while adjusting the trim and in no wake zones. After getting the boat back to the dock, I pulled my multimeter out after checking the wires to the plugs and found the voltage of the battery dropping from 12.8 to 12.4 when running and 12.1 with the blower motor running. I suspect this is the alternator.

I am pretty handy with cars, however, new to boats. So far I have found out that it is never okay to put an automotive alternator in the boat because of the marine ignition protection.

My Alternator is a Mitsubishi with a regulator mounted on the back, 3 wires coming off the alternator; The store in town has a 1 wire marine alternator, which is supposedly a fit for the boat.

My Question, can I use the 1 wire alternator? (I doubt this but I'd rather check than not) Or should I rind a replacement to be shipped?

Thanks to all for taking the time to read and respond.

 

[Bt Doctur]

the 1 wire should be a bolt in.just remember you need atleast 1000 rpm to start the charging.

 

[THenning]

So A OK to go from the 3 wire alternator to the 1 wire? I.E. I have a Motorola Style in my boat, OK to switch to a Delco Style?


Measuring at about 2,000 RPM Still no jump in voltage.

 

[Bt Doctur]

a 3 wire has a "sense" (constant 12v)and "excite" lead (switched 12v) and are normally an instant charge . the 1 wire need to be spun up to initially start charging .
then will remain charging

 

[THenning]

All good! Boat runs Great! Thanks!