1975 Merc starts up, runs great, warms up, but then won't restart?

[Grumpy Bear]

So, my 1975 Merc 500 50 hp starts right up, runs great, warms up, but then won't restart (or has a very hard time starting back up) after it has been shut off for a few minutes. Here is what I've done so far: new gas (no ethanol), gas additive (Quickleen), new fuel pump kit, new sparks. I have carb kits coming in the mail. Any thoughts on why it would run great but then not run great after warm up and shut off?

 

[Chris1956]

If you pull up the cold start lever, does that help? I will guess it is flooding. The carb kits should help that.

 

[Grumpy Bear]

Thanks for the reply, Chris. Yeah, I pull up the choke and eventually it will start back up but it has no power and dies when I put it in gear. After several tries, I will finally get it to go and then it's fine again. Weird.