The starter had issues when hot, particularly when trying to re-start after picking up a skier. It has plagued me for several seasons. I finally figured it out after prepping the boat for the 1st trip this summer. I cleaned all the connectors on the starter, did voltage measurements on the ignition switch & throttle/gear disable switch. Those were all good. Finally I could hear a faint clicking from the starter relay:
I removed the relay and jumpered the socket from Pin 30 to Pin 87 (which I remembered from my German car days) and BINGO! it turned over instantly. The pins are clearly numbered on the underside of the relay for identifying which ones to short with the jumper wire.
Then I took the relay apart by drilling a small shallow hole on each side, enough to pry the retainer clips apart and pry thru the holes to pop the innards out of the shell:
Cleaned & sanded the points (which were obviously burned) with 400 grit & sprayed a liberal amount of contact cleaner & blew it out & popped it back together & filled the drilled holes with RTV. Works fine, but I ordered a new one & will keep the old one in the boat for a spare, along with the jumper wire.
The downside is the new Hella relays are made in China, but at least they're hermetically sealed. The new part number can be seen on the box if you zoom in on the 1st pic. The original Hella part number is 4rd 960 388-31.