I got a 1990 omc 3hp. it runs ok but stumbles while under load. After about 7 mins in gear it stumbles hard and looses power then dies. It will start back up instantly. But before it dies if i put it in nutrual and rev it, it will be fine and continue to run for a couple of mins before another "episode". It has good comp. and all kinds of power.
<br /><br />You have a marginal fuel supply problem. When you rev it in neutral it pumps more fuel than it is using, when under load it is using more than it is pumping.<br /><br />Look for a restricted fuel line or pickup, air leaks, restricted vent on the tank, or even a failing fuel pump.<br /><br />Good luck.