alt or starter: HELP needed

[Achilles]

Hi again,
Here,s my problem, 1st not sure if this is right forum. I have 1988 Cobolt with 5.7 mercrusier . I had the batteries on the charger for 2 weeks or longer (on board charger) the batteries are fully charged. we are going out this weekend and went to check to make sure thing was a go. we have not started to boat in a month. so I can understand a little cold start, engine seem slow to start on single battery seem to to dragging.switched over to duel batteries fired right up.
after allowing enough time to warm up. shut down switched back to main start battery started with alittle drag but started. after checking a few more items. shut down went to restart on a main battery, no go. slow turn and went clicking (Solenoid). again went back to duel batteries fired right up.
gauge reading on single running about 13.8.( not 100% sure if working correctly)After running about 1500rpm shut down on and was able to restart on main.
again shut down and same issue no start, dragging.

the batteries are less than 6 month old.

our first time out on the boat we had problem starting after we had to shut done due to gauge malfuntioning and warning lights came on, the gauges were acting errectic. I figure was a short. as we limp back in to port, boat we stall many times. after check all wiring and connections only problem I could locate was bad connection on main circuit breaker.

Seems to be another problem, I am thinking alt or starter? with all the gurus here I am hoping someone will be able to help.

 

[Don S]

Re: alt or starter: HELP needed

Could be any number of reasons, and none of the include the starter or alternator.
If a battery is fully charged, then it should show around 13.8V when the engine is running. So that is normal.
A dragging starter could also cause the problem.
Here are some other things that can cause the starter to drag, or appear to drag.
Loose battery cables. (lose the wing nuts. Get regular SS nuts and use a wrench to tighten)
Dirty connection on the battery cables. (Clean the corrosion and tighten the nuts)
Defective cables (loose corroded ends with green cable inside the sheath and heat shrink) (Replacement is the only fix)
Defective battery switch. (Hook up a known good battery directly to the starter and ground and see if it works.)
Water in the cylinders. (Pull the spark plugs and crank the engine and see if water comes out or there is rust or water on the spark plugs.)

 

[Zackman]

Re: alt or starter: HELP needed

Here are a couple of tests to build on Don's comments about battery cables and connections. I would also check the battery to be sure there is no draw with everything turned off (maybe a secondary problem).

Voltage Drop Test

Per the Mercruiser Manual

To test the positive cable / connection:

- connect voltmeter positive lead to positive battery post.
- connect voltmeter negative lead to stater solenoid's positive connection.

** be sure to remove one voltmeter lead before cranking stops so you don't damage voltmeter **

- Crank engine... voltage should not exceed 0.5 volts. Greater than 0.5 volts suggest high resistance in positive cable / connections.
.

To test the negative cable / connection:

- voltmeter negative lead to negative terminal on battery.
- connect voltmeter positive lead to starter ensuring good contact with metal.

- Crank engine... voltage should not exceed 0.5 volts. Greater than 0.5 volts suggest high resistance in negative cable / connection.

In both cases connect to the battery terminal and not the cable at the battery, since you are testing the cable and connections.

Battery Draw Test

To check for a draw on the battery (such as CO Detector) and you have a test light, you can do the following:

Remove the negative battery cable from the suspect battery.
Attach one end of the test light to the negative cable.
Push the other end of the test light "ice pick" end into the negative post of the battery.

If test light glows, then there is a draw on the battery. Begin disconnecting suspect items (e.g. CO Detector) and recheck.

 

[Achilles]

Re: alt or starter: HELP needed

Thanks, I get on it tomorrow, Good thing I have a short day at work tomorrow.

 

[wan2live]

Re: alt or starter: HELP needed

I have a dual battery setup and my main cranking battery would charge fully but would not crank so I had it tested an low and behold it was bad so I would also get you batteries tested if you have a store like advance or autozone around.