Mercruiser 3.0 I/O starting problems, new battery and stereo ?

keston925

Cadet
Joined
Jun 9, 2015
Messages
14
Mercruiser 3.0 I/O used to start up nice, but recently I thought I had a bad battery. At the same time I kept having problems with the stereo cutting off while driving. We replaced the battery and stereo, but the stereo now ALWAYS cuts out when the engine is on. AND now the boat wont start at least not easily. It clicks when the ignition key is turned and eventually will start but its getting harder and harder.

Are the two related? A mechanic suggested to me that it might be a bad starter? I am wondering if the problem may be more of a more simple wiring issue?
 

Grub54891

Admiral
Joined
Jun 17, 2012
Messages
6,298
ok,lets get a look at this. the problem existed before the battery and stereo were replaced. now even with new parts,its getting worse. I"d say you have a bad electrical connection someplace. Lets start at the battery-make shure the connections are perfectly clean and shiny.check the connections at the starter also. now check the engine ground,by the back of the motor,take it off,clean it thourghly,re-attach. then give it a try. let us know what happens from there.
 

Silvertip

Supreme Mariner
Joined
Sep 22, 2003
Messages
28,771
Just because you have a new battery does not mean it is being charged when the engine is running. What does the voltmeter read with the engine at 2000 rpm? Electrics have high and low voltage cut-off circuits that results in exactly the problem you are having if the battery voltage is too low or too high. It also is the cause of the click rather than the starter spinning when you turn the key. Battery cables, battery cables, battery cables is always the first place to start when weird and not so weird electrical problems occur.
 

keston925

Cadet
Joined
Jun 9, 2015
Messages
14
Thank you... I am going to see if I can figure this out....

I should add that the trim switches weren't working at one time as well, then magically they worked again! I am thinking this is all related... wiring/battery cables
 

Silvertip

Supreme Mariner
Joined
Sep 22, 2003
Messages
28,771
Don't ignore my question about what the voltmeter reads with the key on and engine not running and again with the engine running at 2000 rpm.
 

keston925

Cadet
Joined
Jun 9, 2015
Messages
14
Don't ignore my question about what the voltmeter reads with the key on and engine not running and again with the engine running at 2000 rpm.

Thank you for this great advice... what am I looking for with the voltage meter? What will the voltage meter reading tell me?
 

lmuss53

Lieutenant Junior Grade
Joined
Sep 9, 2008
Messages
1,227
That will tell you if your new battery is charging. A perfect battery with perfect wiring will do just what you describe if it is not recharging properly. You want to test the voltage before you start engine and then after. You want to see a significant increase in the after reading, like 13.? something volts or even a little more with the engine running.
 

Silvertip

Supreme Mariner
Joined
Sep 22, 2003
Messages
28,771
It will tell you if you wasted money on a new battery only to find the alternator is not working so your new battery is not charging either. A fully charged battery will read 12.6 volts with no load. If your boat has a voltmeter, just turning the key ON but not starting the engine, the voltmeter will read static battery voltage (12.6 volts minus any losses going forward to the helm). If you start the engine and increase RPM to 1500 - 2000 the voltmeter should rise to 13.5 - 14.5 volts. That says the alternator is working. If there is no change in the reading then the alternator is not charging.
 
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