90 hp slow cranking won't start

[Dusty001]

We have a 1993 14 ft jazz Bayliner with a 90 hp mercury motor when we turn the key it cranks slowly but never actually starts. Replaced battery, Took out spark plugs and turn key cranked fine but won't crank once pressure is back in. Anyone have any ideas.

 

[ChrisD2725]

Sounds like the starter is failing and need replaced.

Chris

 

[DavidMoore]

You could try to strip out and clean the existing starter motor, I had one with rust sticking to the magnets and doing exactly what you describe. A quick clean brought it back to life.

It's an easy job, 2 bolts and it all comes apart. Just remember on re-assembly to use the alignment marks and that a CD case with a slot cut out of it will help to keep the brushes in place when putting the armature back in.
Worth a shot?

 

[Frank Chyz]

Had something similar with a 1988 100HP Merc OB. Had it stored over the winter at marine repair shop. Would not start in the yard when I went to pick it up in late May. Tried charging the battery, even used one from the shop. No go. Mechanic took out the starter, brought it to the bench & worked on it for a few minutes. When he replaced it, started right up. I don't know what he did exactly but he did mention that I should consider replacing the brushes at the end of this boating season. Been running fine so far.

 

[Texasmark]

Before you do a number on the starter, get a voltmeter somewhere. Ditigal Multimeters are for sale everywhere cheap. Put it on the 10volt dc scale. Put one lead on the starter input power terminal...red wire, and the other on the battery - connector. With your new fully charged battery, and voltmeter connected, put the ignition switch in the START position and read the voltage as you do. If less than 10v your problem could be dirty terminals between your battery and starter. Clean and bright and tight is the slogan and that's inside where the current flows (take them apart to clean properly not just on the outside.

That won't cost you anything but a little time and needs to be done periodically anyway. Then try again. If voltage is still low then go after your starter as directed. Nothing special about an outboard starter. If you have any auto engine manual lying around find the starter section and read up on how to check and clean a starter.