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It looks like the diagram that you're constructing looks right, but there are a few things that you need to consider. For instance, you need compatibility between the Group 27, "DC2DC Charger", and the LiFePo batteries. None of the components of an LiFePo system work the way they do with FLA and it sounds like you know that already. I just want to throw some cautions at you and I apologize if you already know them. 
1) That DC2DC charger is not (always) your friend. These chargers can turn current on and off very quickly. These large LiFePo batteries are able to be charged at 100+A and can turn that charge current on and off in microseconds. This can play havoc with your alternator when the DC2DC goes from 50A to 0 in an instant and your Group 27 is already "floating" and not able to accept any more charge current. I believe there is a way to put in a shunt resistor at the alternator to prevent issues from occurring, but I'm not familiar with how this is done. See the issue that the Wynns had (Gone with the Wynns) on their new catamaran. Their LiFePo setup cooked both FLA batteries.
2) When the alternator is off, the charge current to the LiFePo bank is effectively limited by the characteristics of FLA Group 27 battery you put in the system. If you set the DC2DC charger to 50A, you need to make sure that the FLA battery can sustain that current drain without overheating. In your picture, the FLA looks like it's in series with the DC2DC charger. Since I don't know how that would work (without some massive diodes) I'm guessing it's actually in parallel with the house bank on/off switch and the alternator. See #1.
3) Based on Ah ratings, if you're trying to get the most life out of LiFePo batteries, they're not going to supply any more power than FLA. Most battery manufacturers should give you this information. For instance, Victron batteries can go 2500 charge cycles with 80% of their capacity when the "Depth of Discharge"(DoD) is 80%, but can go twice as long (5000 charge cycles) if the DoD is 50%. (https://www.victronenergy.com/upload/documents/Datasheet-12,8-&-25,6-Volt-lithium-iron-phosphate-batteries-Smart-EN.pdf) That 50% number looks an awful lot like the FLA number. The one big advantage is that you CAN go below 50%, and only sacrifice a little bit of longevity. This is still oodles better than FLA because if you drain FLA batteries, they may never recover. With LiFePo the batteries will continue to work for a long time (just not as long as they would have).

Yikes. We have your (almost) sister boat, Mola Mola, #1488. I don't have any advice, just sorry that you're going through this. Which hose was it? (I'm going to make it a priority to replace that one this year)

When you say "depreciated 80%", was that a rider on your insurance, or is that a standard feature of boat insurance that I haven't had the pleasure of running across yet? The last boat insurance company I had put a rider on the insurance that if the engine was a factor in the claim, then there would be no reimbursement for the engine. It was one of the most bizarre things I've read. I even asked "so if my engine dies and then I end up on the rocks, you will reimburse all damage, except for the engine?" "Yes" "Even if the engine is further damaged by being on the rocks?" "That's correct. if an engine issue is found to have participated in the claim in any way, the engine is not covered" I switched insurance companies because they started attaching riders.

I talked to Warren Pandy at Catalina, if you have any questions, you could point your questions at them.

Here's the pdf drawing that Catalina sent me. Yes, they are drawings for other Catalinas, but they assured me that this assembly exists on the MkII after 2001.

You are lucky!

From my conversations with Catalina three years ago, there are replaceable bushings that are relatively inexpensive and moderately convenient to replace. You still have to drop the rudder, but the bushings are right at the top and bottom of the rudder tube. I can't seem to figure out how to attach a pdf to a post, once I figure that out, I'll do that.

I say you're lucky because even though I have a MkII, Catalina didn't change the rudder post design until well after Mola Mola was made. It has the old style rudder tube where your only resolution is the West System solution with graphite impregnanted epoxy. You coat the rudder stock in mold release, put the rudder back in the tube, and then inject rudder column with epoxy in three different places. Pray that you put on enough mold release so that there are no bare spots.

https://forums.sailinganarchy.com/threads/j36-rudder-bearings.67191/

The most obvious solution is to address the movement at the top of the shaft with sheet shims or a 3D-printed top shim, as per the advice on this forum. But I'm not sure if this is the complete solution. Does that much movement indicate that the lower hull bearing is shot and also needs replacing? What else in the rudder system should I be looking at?

Arguably, I'm spoiled. On my C28, I had a M25XPB and on the C34 we have the M35BC. In both cases, I've appreciated the boat speed we were able to maintain in 20kts of headwind with the sea state to go along with it. In both cases, we happily clipped along at 4.5-5kts. I attributed it to both boats being slightly overpowered for their size and weight. I wonder how true that is, though. Of course we're talking theoretically, but I wonder how much different it would be with the M25 in the C34.
Mark
Mola Mola 1488

Previous info about my "no aft smile" and the loose aft nut (in no particular order):

I think that the only way you will really know the answer to this question is if you have a mechanical engineering friend. Knowing that type, turn it into some kind of bet and offer them a case of their favorite beverage so they do a "Finite element analysis" of the keel/hull joint blocked in the front or blocked fore and aft.

Logic dictates that the bolt isn't stretching, but the piece of keel that sticks out forward of the forward most keel bolt can bend. I'm not saying it does bend, I'm saying it "could". FEA (finite element analysis) would tell you exactly how much force you would need to create a "smile"

Mark
Mola Mola

Ron,

that's a good suggestion, and one I'm going to do at the end of July. For now, I just slapped some antifouling as best as I could and will deal with it then. This should be sufficient until then, no?

Mark : Here is what I do before the spring splash. Late in the day I have the yard lift Apache up so I can examine and bottom paint the underside of the wing.  Then the boat hangs in the slings there overnight and lets the paint dry. I'm the first splash the next AM.  Works well.

A few thoughts

Good question. Only that the rest of the hull has it. I hadn't even thought about doing something different. If primer is all that's needed than great! But I wonder, then, why did Catalina gelcoat the keel?

Honest question, inquiring minds want to know.

What's the purpose of paying to epoxy-barrier-coat a lead keel? 
A barrier coat is to prevent blisters from forming on a polyester-fiberglas hull.

Isn't a good paint primer enough on a lead keel?

-Ken

[You both are saying the same thing.]

You are absolutely right. I (mis)read his post three times before answering and still got it wrong. Thanks for the correction. I had this fight with the yard last fall and couldn't see what he was actually saying.

all the weight should be on the front of the keel only.

blocked with.... 25% of the weight on the nose of the keel. 

Mark,
You didn't say what % of weight should be on pads vs the keel, but, above, parsing out the pertinent information ... You both are saying the same thing. 

Weight should be supported at the nose (ie., forward part of) the keel. ***

I trust that you are not saying there should be no weight on pads (be it jack stands or a cradle)???

PS: ***Do not read into this I buy into CTY's fantasy explanation of what causes a smile.

I'm getting what looks like gelcoat chipping on the bottom of the keel. Five years ago, the PO shell blasted the bottom and coated with two coats of west system barrier coat. The yard looked at the bottom of my keel yesterday and said they never did the bottom of the wing. Offered to put me in the slings for a day or two in July for me to grind it off and barrier coat the bottom of the keel. Sounded more than fair. I mean, I'm sure they're going to charge me, but they said it would just cover their costs.

Is there anything I'm missing from this? Anyone do this job and found it to be more onerous than they thought?

Mark
Mola Mola #1488

Ron,

I'm not one to disagree with you and your experience, but the mechanical drawing from Catalina shows blocking only on the front of the wing keel. Mine is a Mk.II, so there might be a difference, but for Mk.II wing keels, all the weight should be on the front of the keel only. Next time I'm down at the boat, I'll take a picture.

Mark

dan : Disagree with you on the cause of the smile.  I talked to the factory many years ago and they recommend that the boat be blocked with 75% of the weight on the jack stands/cradle and 25% of the weight on the nose of the keel.  Also VERY important to get the jack stand pads on the bulkhead!!

A few thoughts

If you go with a "triducer" (depth, speed, temperature) you will only need one through-hull. Resulting in you having to seal up one of your through-hulls and probably replace/alter the remaining one to accommodate the triducer's size.

I can verify this. I bought the Raymarine all in box set with wind, knot meter, depth and temperature and a couple of i70 displays. All was installed except for the triducer. It was a DST810 and does not fit in the same size through hull. I was going to leave the old depth sounder in there, rather than doing all that glass work.

In retrospect, I would have bought the B&G for all the great sailing features it has. Especially when paired with one of their chartplotters.

Mark
Mola Mola #1488

Our C28 (Also an M25XPB) had black soot in the engine compartment in line with the alternator. Turns out it was he graphite from the brushes.YMMV

Do you mean Sailrite? I couldn't find anything on Sailtite, but I'm not a great googler.

Check on the Sailtite website and/or call them. They have some fast draining (open cell) for cockpit cushions, in three different firmnesses.