Thanks for the mast head sheave layout. My spinnaker halyards are in the masthead sheaves though having not used then yet, no clue on fiction. I was wondering about three easy way to gybe the spin pole so that makes sense with a two pole layout though I only have one aboard as well. Can you give a layout the same way on the foot of the mast where they all exit?
Hummm... Working from memory, on the starboard side of the mast from front to rear: Spinnaker Halyard, Spare Jib Halyard, Empty Slot for Starboard Pole Lift (Not used), Main Halyard. On the port side of the mast from front to rear: Secondary Spinnaker Halyard, Primary Jib Halyard, Pole Lift, Slot with Messenger for Secondary topping lift, Spare Main Halyard, Topping Lift. (I will check to ensure that the foregoing order is correct but I think so.) Note that the chafe on the spinnaker halyard at the masthead is a real PITA and not many are too thrilled at having to go up there at sea to replace the darned thing when the it breaks. You can add the masthead crane or, alternately, wrap the last 5 feet or so of your spinnaker halyards with Kevlar tape and replace it as necessary (in hindsight I might do that.)
I actually have a removable inner forestay though but it is connected into the mast about halfway batten the babystay and the forestay. On deck there is an extra padeye behind the anchor locker which ties into the bulkhead before. It has a mechanical fitting to tension which can be removed but no obvious halyard sheave near it other than those fir the pole lift. I'm guesting this wasn't standard with the boat. I'm figuring it's either for a staysail downwind or storm jib.
I am assuming your intermediate stay is connected to the mast at about where the slots for the runners are and, if so, your good to go. The tang likely has a spare hole for connecting a swivel block to take a staysail halyard which can be run externally. This is an excellent arrangement and when the stay is set up, you can dispense with the baby-stay which can be moved over and temporarily secured at the lower shroud base leaving room to carry a dinghy inverted on the foredeck. Friends of ours with the same boat (Ocean Angel) who are now waiting for a weather window in Great Bay, Peter Island, BVI for a passage to St. Martin, have this same arrangement and are very happy with it. The stay works for a hanked on storm jib or a non-overlapping staysail which is very effective in heavy air. You might care to correspond with Ocean Angel. They can be reached through their website at Sailing with Ocean Angel
My Perkins is interesting. I believe the propeller is pitched wrong. I pull nearly 3200 rpm to get to the same speed as you with a clean bottom though fuel usage it's about the same. I've been told by another Perkins owner that theirs was the same but they replaced it ten years ago due to some failure so maybe their memory was wrong. The prop is a two blade non folding. No idea on make.
Either your tack is wrong (given the fuel consumption you quote) or the you have an under sized /under pitched prop. (I've not seen a First 42 with a fixed prop so yours might be a replacement?) Our prop is a 10x20 that is a bit over diameter but works well enough. At 3000 RPM I'm pushing 8-1/2 to 9 knots but the fuel consumption goes way up. Our engine is happiest at 2500 to 2800 RPM which keeps us in the 7-8 knot range. We do push it once in awhile but not often (usually only when my wife is tired and she wants to get home "right now" or we're trying to dodge a squall or a ship.) Ocean Angel has a folding 3-blade that I believe is 16" diameter. A bit small but with the added blade seems to work well enough and is quite smooth. As/When/if we win the Lottery, I'm going to switch to a 17x12 3-blade Flex-O-Fold which is very smooth and efficient (in 2006 I was quoted $1600 for that by Cruising Solutions but the price has certainly increased since then).
One thing that you might want to look into a changing out the air intake filter on the engine for a KN Filter, RX 3800 (See KNFilters.com). You have to punch a hole in the side of the housing to take the breather from the crank case but that's easy enough. The through-put is much improved which makes the engine quieter and the crank-case pressure is reduced which really reduces the oil seepage around the rear seal which is a universal affliction of 4-108's.
The 4-108 really is a very good engine and, considering the use in tractors and generators world wide, parts are pretty easy to obtain and repairs effected. As/When/If mine ever needs it, I'll rebuild it before changing to a different engine.