Re: Help with 30 hp evinrude
welcome to iboats. 99% you have a bad clutch dog. is it tiller or remote controlled. the gears in the lower unit are very square edged, from shifting slowly ( hearing the gears mesh) these edges get worn, and rounded off. thus, when the load is applied the come out of gear. almost like hitting a log.
if it is remote controlled the cables could be misadjusted, and not going all the way in gear. or the shift linkage could be misadjusted.