I have a 1991 force 150hp outboard and I think that the rectifier is bad because the battery does not seem to stay charged for the day. the battery is new and I have had it tested to be sure it is not the battery. While we are running the motor, the volt guage will start at a little over the 12 and drop during the day to a little over the 10. The starter was replaced last year but it seems to turn over very slow and sometimes you have to put the battery switch to all to turn it over. Is there a way to test the recitifer or do you have any other suggestions?