A 1GM10 + a three bladed prop will make useful progress to windward in any conditions you would want to be out in and has enough power to 'dodge' to windward in a gale at an average of 0.5 - 1 knot flat out in any sea-state up to more than sufficient to roll the boat, so can keep you off a lee shore for as long as the fuel and helmsman hold out. (BTDT till the tide turned).
Installation is fairly simple as such things go for anyone experienced. Assuming existing engine beds in approximately the right place and a pre-existing suitable shaft, you could even get away with doing it afloat!
If you already have a diesel fuel system, single lever control, waterlift exhaust etc. you could be pleasantly surprised how easy it is. The control panel and idiot lights are so simple you could probably splice into the loom to your existing panel.
The Yanmar mounts are pretty soft and it does bounce around a fair bit. Beware of stress on your shaft seal, you may want to add a plummer block or other mid-shaft bearing + a flexible coupling.
Aftermarket mounts, shielded for oil resistance and that do NOT require lock-wiring for blue water use (unlike Yanmar ones) and approx 1/2" lower profile are available from R&D Couplings for approximately 1/4 the price of the Yanmar ones. You may even come out ahead if selling on a brand new set of Yanmar mounts.
They are a bit stiffer so more resonances, but not a problem as long as you don't keep it running at the resonant speed for long.
You can actually set the idle low enough to get 'dead slow' as your minimum speed in gear for ferry-gliding against only 1Kt of tide/current. (Hint: adjust the control so the throttle doesn't start to pick up till you are out of the detent for slow ahead/astern for better controllability.) Up to 100RPM less than the official idle speed should work fine, just tune it to avoid unwanted resonances at idle. Don't go more than 50RPM on the high side to avoid excessive gearbox wear when engaging gear.