Bf 7.5

I have what I believe to be a 1986 BFS 7.5 hp Honda. We took it out fishing today and everything was fine. We got to the channel and floored it to get out to our destination at Crystal River. It ran full throttle for about two minutes then died out then a small cloud of smoke appeared around the motor. I tried to take the motor out of gear but it was locked in forward. What would cause this? I was able to get it out of gear maybe an hour later after trolling around. I always check oil level before starting and once it is running, ensure the motor is running cool water. Any help is greatly appreciated.

When is the last time you looked at the water pump impeller ?-----Checked the gear oil on this motor ?

Changed gear oil two years ago when we ran it. I changed the impeller around the same time. It has a strong stream of water. The only reason I didn't change gear oil is because we have run it maybe three trips of an hour on the motor each time. I didn't think it was significant enough time to need a change. Maybe the Florida weather is to much and will still need a change?

On some motors you can not take it out of gear when the tiller handle is still at full throttle.----Sorry I was not there to see what happened.---Could be as simple as a plastic bag blocking cooling water to the pump !

It wasn't taken out of gear, I know that for sure. Basically the series of events that lead up to it. My motor has a hard time staying running but once it gets warmed up, it will go all day. Until it gets warmed up, what it will do is idle fine, then throw it into forward, it will studder then die if not immediately throttling it (sometimes it will die anyway if you even throttle it). We were heading through the back channel and into the channel leading to the Gulf of Mexico. Once I straightened up and made sure via depth finder I was in the channel and no risk of oyster bars, I full throttled it. It ran full throttle for about two minutes and then spuddered once then died. I believe it was small white smoke cloud I saw but can't remember the color 100% but remember a burning smell after the smoke appeared. I tried to pull the gear lever up into neutral out of forward but it was stuck in place. I trolled back toward the safe area of water due to only being on a trolling motor. About an hour later I tried taking it back out of forward and was able to without any resistance. I then tried to start it back up and was able to and cruise with it for a little but I was to afraid of destroying the motor. The only thing that really sticks out that might have gummed up the water vent is seaweed that I passed but even then, I remember looking back to ensure the water was running, which it was. I am stumped with this one. Maybe I will have to take it out on my local lake and try to recreate it.