1981 evinrude 9.9

First off just found this forum so first post looks like a great site scrolled thru a bit lots of good stuff. I am new to having a boat in general really had a few here or there but never worked on any. Iz traded for a 14 ft v bottom with a 81 9.9 evinrude . Motor will start really easy at times and when it does it runs great and has a lot power and good and smooth. Then at times it just won't start then all the sudden will fire right up. After being stuck in hot sun for almost a hour trying to get it running I'm really getting tired of it lol. One problem I know is the red lock(?) Keeps slipping over and catching the rope and as you all know that just stinking hurts bad after a few times
Anybody got any ideas what could be going on .

Thanks for a great forum

Id start by giving her some seafoam and making sure the carb is clean. (sounds like it might have been sitting a while) Second id make sure your kill switch isn't sticking. you can do that by disconnecting it and make sure you have spark. A new spark plug never hurts

when you test your spark you need to buy or make a spark tester. holding the plug on the head and cranking it and seeing spark means absolutely nothing... sounds like what the above poster said and it may have sat for a while. start at the gas tank and check everything from there to the carb, if the carbs getting fuel you may have a lil piece of something clogging up the carb.

I agree with the others, it sounds like you should do a carb cleaning, making sure there's no trash or water in the float bowl and finish it off with some new plugs and possibly plug wires if needed. And it never hurts to go through the fuel supply from tank to the cylinders.