slow cranking engine

[jeff]

hi guys i have a maxum 2800 scr single, my problem is the engine is cranking real slow like the batts were on their way out , one was low so i replaced them both to be sure,it still cranked slow, to slow to kick the engine over, i took out the plugs they were a little dark two had a little corrosion on them so i got new plugs while i had plugs out i cranked her a few times in case of hydro lock but even with plugs out the engine cranked real slowly,i was thinking starter motor i mean it is cranking but very slow,, any ideas

regards
jeff

[jeff]

I'm sorry i have a 7.4L mpi mercury v8 2001

[mmwjr]

Jeff you need to check for voltage drops before replacing the starter. Corroded electrical connections add resistance which results in voltage drops and limits current flow.

Are the battery cables clean and tight? Same for connections on the battery switch.
Battery return (ground) including connection to the engine block.

If above is good go go next line.

Start at the slave solenoid which may also have pitted contact causing the same issue. With a voltmeter measure for 12 V when cranking on both terminals of the slave solenoid. If ok then do the same at the starter.

If no drops are found and a solid 12 V is on the starter heavy batter terminal then it is time to replace the starter.

[jeff]

thank you mike,, i will check those things out and let everyone know,
regards
jeff