Especialy good on the Yanmar reverse facing pumps. Can replace the
impeller by feel. BRBR

I've got the Yanmar 2GM20F with the waterpump facing aft. It would appear that
this model for require the SpeedSeal with four thumbscrews. Is that correct?
If so, it also seems that two of the four would remain in place as you slide
the cover into their slots and then put in the last two thumbscrews. How
difficult is that to do by feel as you would not be able to see the screw
holes?