Thanks for the referrals, I will follow up with them.
The other thing that makes me suspicious the problem is more than the stuffing box, is that is mounted on a flexible hose. You would assume if the stuffing box was tight enough to stall the engine the hose would twist or deform in some way and they would have to be some powerful hose clamps that hold it all together.
PS Sorry about the delay in response. Being a noob here all my posts need to go via a moderator.