LT180 - Problem starting

[MainelyMower]

Hi all
I have a 15 year old John Deere LT180 that runs like new if I can get it started. My problem is, on occasion, I turn the key and get a single click. I keep turning the key and sometimes after 20-30 turns of the key and single clicks, it will turn over and start right up. Cranking strongly. I have replaced the battery several times as well as the safety interlock switch on the parking brake twice. Has anyone had this problem or have thoughts on what could be causing it? I have kept it well maintained with tune ups, oil changes and blade sharpening/replacement.
Thanks

 

[StarTech]

It is likely the starter solenoid having burned contacts and replacement should fix it but I do that some these mowers needs a helper solenoid too.

 

[mikebarber]

Got to agree with Star Tech