Volvo/Penta-280dp diesel conversion question

Have the diesel, a Perkins 4-108

I found a couple of Perkins diesels, and bought both of them. I have a 4-108 and a 4-107, not much difference, both have transmissions, but I won't be using them.

I moved the boat from Lake Kissimmee to the St. John's near Palatka, and we have ran it a little. It seems the Ford 351 probably has the harmonic balancer and pulley off of the 302 it came with. It still has some vibration, but doesn't smoke and after some carb work, it actually runs very well.

I am going to tune up the diesels (Westerbeke Marine) and after they are running well, make the swap.

I run the gas motor at around 2500 rpm and the boat goes the speed I want to go with the diesel, so the gearing will probably work ok.

Somewhere in the process, I lost the small prop of the two, it just came off. I hadn't had it out, so I don't know what was loose, no telling. I am wondering if I could go up slightly in pitch, realizing at the same time, that I can't make up gearing with pitch without loosing torque, another boat quandary.

PJ