The 2.21:1 mentioned on your gearbox (which is the same as mine) is the gearbox reduction ratio as the propellor turns slower than the engine, so, on your gearbox when you are running at say 2800rpm the prop is turning at 1266rpm The two other reduction ratios you can get on Yanmar 1GM10s and 2GM20s are even greater reduction, 2.62:1 and 3.06:1 but you would need to swing an even larger prop with greater pitch to get similar performance, which is fine if you have the space and tip clearance for a larger prop but doesn't work on the Parkers. I am very interested in your cockpit locker stowage for a liferaft, as I have been wondering where I could fit one in my boat as I would like to go further afield (France and Ireland) and a liferaft would be prudent. If you have a chance to send some dimensions and or pictures would be great.
I am slowly sorting out the logistics and amassing the various bits and pieces needed to carry out the swap. I am making a steel framed lifting cradle with a rolling carriage so that I can first lift the engine from the side of the boat into the cockpit then moving the framework over the cockpit and companionway, I can then lift the old engine out, lift the new one in then move the cradle again to drop the old engine over the side. the cradle consists of a a length of thick wall 40mm x 40mm steel box section (rounded corners) with end plates to which are attached 2"x4" timber legs that span the cockpit then a dolly made from 2" nylon for the roller and two side plates with a 10mm bolt as a axle and a lifting pulley arrangement hanging off it. To clear the galley and allow me to swing the engine in beneath it, i have made up a "C" frame, also from 40x40mm thick wall box section with lifting points on the extremities, one connected to the engine lifting point and the other used to lift the whole arrangement. it is 24" on each side. This should obviate the need to try and slide the engine in and out which would have caused problems with the sump catching on the sill of the engine bay bilge sump which I did not want to cut down as it may allow bilge water to end up in the cabin in the future.It will also mean I can position the engine, mark the fixing points then lift it out to drill the holes for the coach bolts, then swing it back in again without too much difficulty. I have checked and with the front of the engine in the same position as the old engine, I can still get to the shaft coupling from the engine bay, it being only 3" further back, it also means i can still retain the waster strainer in the same position in front of the engine which is where it was before and is easy to access by removing the steps, it also means i don't have to redirect the ducting for my Eberspacher which is ducted over the top of the engine on the portside before turning down right at the front to a floor level outlet. (The Eberspacher is fitted below the cockpit floor, in a position approximately below the throttle lever, trying to use some of the huge amount off unusable space below the cockpit floor. As I say, the idea of being able to fit some form of cockpit floor locker to stow the liferaft sounds very appealing. Is yours a sealed box below the cockpit sole or simply a watertight access hatch to the whole space? I will try to send some pictures of the whole arrangement, once I am ready to go.