1977 85hp cuts off when put in gear in lake but goes in gear on muffs

I just bought a boat with a 1977 850EL 85hp.. runs great on muffs but the 2 times I've tried to put on the lake it runs and Purrs great... but as soon as it's put in gear it shuts off.. no sputter or any thing just shuts off... what is my problem ? Please help... new info.. just investigated and noticed gas pooled up under carbs.. would that be my issue 

I read the link, and it did have some good advice.  However, I doubt it is the ball, as that is under a negative pressure, If it were failing, air would leak in, gas wouldn’t leak out. 

Also, those older carburetors are  known for failing with today’s fuel. 

The pool of gas is a definitely a clue.   

This may sound crazy, but I believe it may be a fuel delivery issue with the carbs.  On the muffs you have absolutely no resistance and the motor has to do very little work.  Put the boat in the water and the prop has to move the whole boat (lots of resistance), and more work = more gas that your carbs can't provide. 

Just a hunch, not a mechanic, but do enjoy wrenching on my own stuff and trying to figure things out... 

My guess would be carb rebuild and a lync and sync.

Yes it will run all day in the lake as long as it's in  neutral ... but when I click it in gear poof it cuts off... on muffs it runs great.. I can put it in gear and get the prop spinning and rev it up... I did some investigating and found a pool of gas under the carbs... would the cause it to cut off when put in gear on the lake?

I am not a mechanic but can search google. Not sure if this will help. Good luck!

https://www.thehulltruth.com/boating-forum/98396-engine-stalls-under-load.html