Starting Problems

[ROBERTWYMAN]

I have a 2000 100hp Yamaha 4 stroke. Both batteries check out excellent. My problem is motor does not turn over fast enough to start. Also drags down batteries. I pulled the plugs and it turns over faster but still slow to me.

[jb123]

check to see if batt cables are getting warm, sounds like your cables are wicked/corroded

[ROBERTWYMAN]

Wires not warm. Boat was rewired march 2010. Checked all connections and all ok.

[99yam40]

Pull starter and have a starter rebuild shop check it out, I have also seen start relays with burnt contacts not making good contact internally, if that is not your problem then you may have a major problem with the motor internals.( bearings or pistons)

[rodbolt17]

do a voltage drop test. that will eliminate or confirm a cable or a connection point.
after that its either in a mechanical bind or the starter failed.