1974 Chrysler 45hp won't start

I recently bought a boat with a 45hp chrysler. After a bit of work, I got her running well, and we had the maiden voyage today. She ran great for quite a while. We stopped to swim for a bit, and then when I went to fire it back up, it started, but quickly stalled. Tried again, and same thing. Tried one or two more times, and then it quit even trying. I have plenty of power, gas, etc. What I came to find out is that it wasn't actually coming all the way out of gear when I thought it was, so I must have been attempting to start it in gear. I'm thinking this tripped/blew some safety or fuse or something to protect the starter/ignition. Anyone familiar with this? I'm sure it's simple, but I'm kinda new to all of this.

Thanks in advance!
Alan

No safety or override on that motor.
It does have a neutral safety switch.If in gear it won't allow it to turn over.
Do a compression and spark test.
Clean the carb and make sure the diaphram in the pump is ok.J

Thanks for the tip J - I just need to get to know the motor & shift/throttle nuances a bit better. After I confirmed it was in neutral, it fired right up. I couldn't find coils for this motor anywhere. Went to like 6 different stores/marinas. Then some oldtimer down in Ohio told me to use genaric car coils. Worked like a charm, and now the thing runs great! Does that raise any flags for you, or should those coils last like the OEM ones?

Lots of people use them.
Not positive but make sure they have the resistor in the coil.

Ok Jerry, new one for you: Everything's been fine with the motor - been out a few times now. Tried pulling the kids skiing today, and I screwed something up. It'll work ok under low load, and even slowly get up on an almost-plane, but under any significant load, the engine revs, and I lose all propulsion. Sheer pin? Shredded lower unit? As always, thanks in advance for your insights.
Alan

Spun prop hub.Needs new prop.
Make sure you get the same size.
Wrong prop = poor performance and excessive gas usage.J

Makes sense Jerry. I've looked a ton online already, and have been to my local West Marine store. Seems like a tough prop to find - any suggestions?

e-bay or this site sells them.
The local Mercury dealer.
Just take your old to the dealer.They can get it rehubbed.
What size?? Should have some #s someplace on it somewhere????