7.4 merc 1996 Hard to start

samm835

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Dec 12, 2006
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575
I have 1996 mercruiser 7.4 carb engine. I put two new batteries in last spring, along with Noco Genius charger. Everything ran great over the summer, I went out to the boat this past weekend to check her out and went to start her and the batteries seemed like they were half charged. I look at the charger and it was flashing green/red which means it's not at full charge and is charging the batteries. They have a warranty so I thought something might be wrong with them. I took to batteries plus and they said they are ok(but low in water). I took back to the boat, reinstalled them and I'm still having the same issues. Anyone have any ideas of where to start? If they were right, and batteries were ok, could it be a starter about to go out? It's slow starting, then clicks as if no charge.i might just force their hand to replace.
 

Bondo

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Apr 17, 2002
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Ayuh,..... Sounds like corroded connections,.....

Could be at the batteries,.....
Could be at the other ends of the battery cables,.....
Could be at the starter,......

All connections have to be Shiny metal Clean,......
Any discoloration, is corrosion,.....
 

samm835

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Dec 12, 2006
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575
When I took the batteries out I cleaned all surfaces and made sure they were tight. The only way to test a starter is to take it out correct? Ugh....taking that joker out if NOT an easy task in this engine compartment!
 

TBarCYa

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Apr 13, 2005
Messages
781
When I took the batteries out I cleaned all surfaces and made sure they were tight. The only way to test a starter is to take it out correct? Ugh....taking that joker out if NOT an easy task in this engine compartment!

Someone here recommended to me that I remove the manifold and riser to get easier access to the starter. The job was quite easy after that.
 

Bondo

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When I took the batteries out I cleaned all surfaces and made sure they were tight. The only way to test a starter is to take it out correct? Ugh....taking that joker out if NOT an easy task in this engine compartment!

Ayuh,..... What about the other ends of those cables,..??..??
 

TyeeMan

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Feb 27, 2006
Messages
849
Your batteries were low on electrolyte, did you bring the electrolyte up to the proper level and charge the batteries?

I presume Batteries Plus load tested the batteries?

I find it hard to believe that a starter would just all of a sudden start to turn over slow. My money is on the batteries and/or corrosion on the starter terminals. Relay maybe?
 

alldodge

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Mar 8, 2009
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charger and it was flashing green/red which means it's not at full charge and is charging the batteries

took to batteries plus and they said they are ok(but low in water).

Agree, fill the bats with distilled water to just above the plates.
Take a voltmeter and measure the bats, they should be at least 12.6V

If not, place each bat on charge and see if you can get them to bring the voltage up. On charge the bats can show 14 or so volts, but after removal from charge, the voltage should start dropping real slow (hour or so) until 12.6

12.6 80% charge
12.7 full charge
 
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