alternator question for a 1990 3.0L mercruiser

I have a 1990 Bayliner Capri with a 3.0L mercruiser engine. It seems my battery is dead or near dead after every time I take it out on the lake. I had the battery checked at the local auto store and its fine. I took off the alternator and cleaned off the cables just to make sure it was clean. After I have a fully charged battery, the engine will start up most of the time with no problems ( sometimes when I turn the key there is just one clicking noise but when I turn it again it starts). When the engine is in idle the voltage meter hovers around 11 volts but does go up slightly when the engine is raised. If I unhook the battery during idle the engine stops completely. Is this normal or is my alternator on the fritz? And what could be causing the engine not to start? Maybe I need a new starter?
Im a first year boat owner but I do know a bit about engines. Any information anyone can give me is very much appreciated. Thanks in advance!

Re: alternator question for a 1990 3.0L mercruiser

Removing the battery cable from the battery with the engine running can blow the alternator, so don't do that anymore.

At idle the alt won't put out any voltage, until you get over it's cut-in RPM. What is the battery voltage with the engine running at 1500RPM, it should be around 13 > 14V if the alt is charging. If you start the engine and watch the batt voltage, while increasing RPM up to 1500, you will see the alt kick in on the voltmeter, if it's working.

I'm pretty sure there's a charging system troubleshooting guide in the adults only section, probably be best to start there and do some troubleshooting. Though, it does sound like you have a bad alternator.

Re: alternator question for a 1990 3.0L mercruiser

The click you hear at start is either coming from the starter itself or the step up solinoid, if it is heard at the starter or the starter has ever been submerged in water replace the starter, the step up solinoid is on top of the engine, if it just clicks you will want to check the larger yellow and red wire for output voltage at the time it just clicks ( no start) if you do not see voltage than it's bad)

Re: alternator question for a 1990 3.0L mercruiser

Thanks for the help. Its very much appreciated!

Re: alternator question for a 1990 3.0L mercruiser

Any decent alternator/starter electrical shop can test bench yours, and you can resolve that concern. Don't take it to an auto parts store that does this, because they will try to sell you an auto part if yours is bad. You have to have a marine alternator, and an electrical shop can probably rebuild your already legal one. The last thing that you want to have on your boat is a non-spark arresting alternator (read: auto)...both for your safety, and to satisfy the Coast Guard if they happen to pull a complete inspection.

Happy boating!