Voltage problem?

[jlj]

I have a 4 cylinder, 2.5L, 120 model MerCruiser. The engine is sluggish when cold started, it hardly is able to turn over. After it is running for a few seconds, I can turn it off and it starts imediately. I notice the battery gauge registers about 11 volts until I increase the engine speed, then the gauge quickly jumps to about 15 volts. What ahould I check? If I suspect the solenoid, is there a way I can test it before running out to purchase another?

 

[sculbert]

Re: Voltage problem?

You have a couple possibilities, <br /><br />Battery - Poor starting when cold either low charge on battery, connection issue or bad cell in battery. <br /><br />Connection - Could cause the volt meter reading and slow starting when cold. But only at battery because the charging circuit feeds back on a different wire than the starting circuit. <br /><br />Alternator - Saying 11 while running then jumps to 15 is systamatic to a regulator in the alternator.<br /><br />I would start with the battery connections and then the ground on the block. I have had grounding problems like that before. It is even possible it is just the battery too. 11 volts doesn't sound too good if you don't have a ground problem you might have a alternator problem. You can use a tester to check the amperage from it to verify if it is working good. If the alternator isn't charging your battery it will do that.

 

[jlj]

Re: Voltage problem?

Battery is brand new. I will check the wire connections along with the alternator. Thank you for the feed back.

 

[Boatist]

Re: Voltage problem?

jlj<br />Need a lot more info. To start with where are your reading 11 volts and when. Is it at the battery terminals before you turn the key on. What is the battery voltage before your turn the key on?? It should be 12.6 at 70 degrees. If it 11 volts while cranking then that is very good.<br /><br />If it 11 volts after starting until you speed the engine I would look at the alternator pulley and see how fast it is turning. Also check the alternator belt tension. If the voltage jumps to 15 volts then your alternator is working fine. I seen a lot of belts slip right after starting when you have max load on the alternator.<br /><br />Slow cranking can be low battery voltage. It can be the type of oil you are useing as it all drains down when setting for a week. It can be water seepping into the cylinders. It can be bad starter brushes or a bad starter solenoid. <br /><br />Place to start is to messure battery voltage before you turn the key on. Then you will know it have something draining your battery or another prpblem.

 

[gisxr750]

Re: Voltage problem?

my boat was doing the same thing i had the altenator tested and it was going bad. so if i was you before going nuts trying every thing else have it tested good luck

 

[Boatist]

Re: Voltage problem?

If the alternator is putting out 15 volts then alternator is fine. Anytime you have 14 volts or more at the battery terminals then the alternator is doing it job. If it 11 volts and the pulley is turning at normal speed then it can be alternator or voltage regulaton.