1985 Evinrude 90HP Battery wont hold charge

I just purchased a new batter

I just purchased a new battery in the spring.Lately the battery has been going weak and will not crank the motor.I put a charge on it and is fine for a couple of times then gradually goes weak.Also the tach has been cutting out then doesn't work at all.Can these problems be related?Where do I start?

" Probably your rectifier is s

" Probably your rectifier is shot. Make sure your cables are in good shape. Feel the ends after starting. If they are hot, they may need work or replacement.

The rectifier converts AC to DC for charging, and is the signal device for the tach. You can damage it by reversing the cables from the battery, or by disconnecting the battery while the motor is running, and lots of other ways. "

"Ray... The following may be o

"Ray... The following may be of interest to you.

(Small Rectifier Test)

Remove the rectifier wires from the terminal block. Using a ohm meter, connect the black lead of the ohm meter to the rectifier base (ground), then one by one, connect the red lead of the ohm meter to the yellow, yellow/gray, then the red wire (some rectifiers may also have a yellow/blue wire. If so connect to that also). Now, reverse the ohm meter leads and check those same wires again. You should get a reading in one direction, and none at all in the other direction.

Now, connect the black lead of the ohm meter to the red wire. One by one, connect the red lead of the ohm meter to the yellow, yellow/gray, and if present, the yellow/blue wire. Then reverse the leads, checking the wires again. Once more, you should get a reading in one direction and none in the other.

Note that the reading obtained from the red rectifier wire will be lower then what is obtained from the other wires.

Any deviation from the "Reading", "No Reading" as above indicates a faulty rectifier.

Joe (30+ Years With OMC)"