The threads on the lower gear case of my DP-SM can use some cleaning up and maybe some minor restoration. These are the threads where the large retaining ring screws in to hold the prop shaft bearing carrier housing and sets the rolling torque of the prop shafts. I know Mercury makes a thread chaser that is 4.375 x16 unc designed to do exactly that on Mercury cases. I’ve measured the VP case and the dimensions look to be very close to those of the Mercury cases including the thread pitch. The Mercury retaining ring also looks very similar although it uses a different spanner to tighten. I have not been able to find a thread chaser particular to the DP-SM. One is available for the SX but I already verified that is too small for the DP case. Anyone know if the Mercury thread chaser will work. I can not get the VP factory specs in the retainer to verify if size and threads are the same.
