Engine won't start vary slow crank with good batterys.

[Sjones2105]

Hey everyone! I'm so I have a Mercruiser 7.4l bravo 3.

She. I turn the motor over it cranks slow. Here's what I have done.

1. Checked batterys charged and Checked voltage. 13.5 is almost perfect and that's what they were at.

2 Checked all connections to make sure they are clean that's from the battery 2 the starter. The starter connection has a little rust but nothing that shjould cause trouble.

3 Pulled plugs and rotated the to make sure there was no water in any cynders.

So far everyrhji g looks normal. So I'm the no g about pullin g the starter... having it tested ? I have had starters lock up but never had one just not turn fast Enough to not start is this a possibility? Also could there be a bad ground somewhere that I didn't check That would cause this? Thanks for the help!

 

[tlewis1]

I'd clean that rust off the cable first ...make sure both ends of the cable are clean and shinny and same to be said about the grounds...follow the ground off the battery and ensure it is tight and clean.

Next step would be to grab a multi-meter and start looking for voltage drop across the starter circuit.

 

[alldodge]

1. Checked batterys charged and Checked voltage. 13.5 is almost perfect and that's what they were at.

The only time you should have 13.5 is while or straight after being taken off charger. A fully charged battery should read 12.6 to 12.7V after sitting for a few hours. Agree with Tlewis1, put the meter on the battery then try cranking it over. The battery should drop no lower then 10V when temp is around 70 degrees

 

[Bondo]

2 Checked all connections to make sure they are clean that's from the battery 2 the starter. The starter connection has a little rust but nothing that shjould cause trouble.

Ayuh,..... Welcome Aboard,..... Take the connections apart, both ends of both, (+), 'n (-) cables, 'n Clean 'em to shiny metal Clean, includin' they mounting points,....
Use sandpaper or wire brush, whatever,... Shiny metal Clean,....

Then I grease 'em to keep 'em corrosion free,...

If the copper wire, inside the crimped ends looks at all Green,.... Ya might need new cables,...

 

[wahlejim]

I agree with all of the above. I would add to load test the battery of your battery tester has that function. But when it comes to connections, i wire brush down to shiny metal is absolutely necessary. Even clean metal with a dull finish acts as a resistor in the electrical circuit.

One way to test for corrosion in the wires is to connect your tester at the starter. Connect it to the post that the battery cable is connected to. Ground it to the engine where your ground wire is attached. Do not connect it to the wires themselves. See what you are getting for a reading. If it matches the battery, then you probably have a bad starter. If it doesn't match the battery, you have resistance somewhere.

If it matches the batteries voltage, you have a starter issue. The starter is not completely shot, but can be rebuilt with what you are describing. There is an auto electric shop near me that rebuilds these things for about $100. They work like new when they are done. Between work and play, I have had about 6 starters rebuilt by them and haven't had a single issue with any of them.