Re: 88 johnson tilt/trim collapsing under load.
The trim range is approximately 15 degrees.
By design, If you operate above the range of the trim rams at over around 1500 RPM, the trim-up relief valves will open and lower the motor back to the fully trimmed position.
The additional 50 degrees of tilt provided by the tilt cylinder cannot withstand the forward operating thrust of the motor above around 1500 RPM.