Alternator upgrade(s) on twin engine

[isophase]

Hi all, working on some major upgrades through the winter on the boat we bought in May. What's below is a bit of thinking out loud and looking for commentary on the electrical systems, specifically the question of upgrading 1 or 2 of the alternators to 24V high-current on a twin-engine boat.



Parameters

Boat: 37ft trawler, twin diesels with original 12V 50A alternators. We get around 200W from solar at peak on a good day. No generator aboard, and don't want one (cost, space, maintenance, noise, exhaust...). The lead-acid house batteries were neglected and visibly bulging at purchase. We used them (nervously) for a very local shakedown season and they've been disposed of now. The AC & DC wiring were a nightmare so this is the right time for rework. I'm an electrical engineer, have access to the relevant ABYC standards, and will do the work myself without cutting corners.

Intended use: Weeks at a time on the Great Lakes, upper St. Lawrence, and related inland waterways in summer months. The plan for the coming summer is a six-week cruise of the Trent-Severn Waterway, Georgian Bay & North Channel. Most nights spent at anchor. We have jobs and young kids in school hence keeping it local-ish and time-limited to July/Aug for now. We might like to venture past Montreal in the long term but for now we'll always be within a day of a Canadian or US port. Not somewhere remote, not reliant on watermaker. We can count on being at dock periodically (1-2 weeks) for provisions, laundry, and pump-out.

Goals

• Lots of nights at anchor in inland waters of/near Great Lakes using primarily solar & battery
• Increase reliability. The existing electrical system gave me enough flaky grief that I'm in the process of gutting it. What I'm finding justifies that 100%.
• Replacing CNG stove which seems impossible to find fuel for with AC induction stove to be used at anchor
• Not expecting to use air conditioning at anchor based on our climate. We do canoe tripping and have chartered in the area, and know this works for the family.

Already decided: Upgrading to Victron-comms-compatible 24V LFP about 400 Ah for the house. It allows higher efficiency and lighter wiring. Upgrading Victron inverter-charger for higher power and to handle 24V batteries with Cerbo monitoring. Looking around at spec sheets, it needs to be at least two batteries to provide sufficient discharge current for the planned inverter's peak loading. We need to do something to charge those as 2x50A 12V would take forever.

The boat will have an electrical panel with 3 sections: 12VDC, 24 VDC, 120 VAC. Current 12V-only loads will stay on 12. Anything 12/24 will go to 24, as will all future replacements/upgrades.


Reliability considerations
Electrical system only - no single vs twin engine debate here!

We do not have and are not planning on a generator. The alternators are the main source of DC charging, with a minor contribution from solar.

Major: the engines must start with very high probability. To that end, we have two 4D starter batteries, isolated, with ability to cross-connect. We carry a spare starter motor. Either battery could fail, and we'd just switch on the other. A starter could fail and be replaced. If the isolator fails, it can be temporarily bypassed.
Navigation equipment (lights, plotter, instruments, radar, radio) must also function with very high probability.

Medium: it would be very inconvenient to lose house loads. That would mean no ability to cook, keep refrigeration, use pressurized water, or flush the heads. That would suck, but in the medium term we're not likely to be more than a day underway from a Canadian or US port where we could plug in to shore, shower, pick up fresh water, etc. Manageable, as long as the engines start. We are not aiming to be in a very remote area or reliant on a watermaker. If we end up with reduced capacity to charge or unable to charge we could conserve.


Charging Options

Upgrade either one or both alternators to high-current 24V with external regulation. For two alternators, it would be a single shared regulator for both alts to manage load balancing and battery charging.

Option 1 - upgrade one alternator to high-current 24 V, leave other stock 12V / 50A
House 24V batteries charged by the 24V alternator and topped up by solar. 0-100% charge in under 4 hours from alternator at 75% of rated capacity.
Both starter batteries charged off the existing 12V alt via FET isolator. Backup plans for 12V supply are to carry the removed alternator as a spare, and probably also a 24/12 DC-DC to charge from the house batts/24V alt/solar.

House battery charging doesn't have a great backup if the single 24V alt goes. Critical get-home loads (nav, radio) could be powered by a 12/24 DC-DC from the starters & 12V alt. That's a very limited power source. It would be spartan for a bit (no fridge, stove, microwave) but safe and not too far to go to civilization. The DC-DC should provide enough for minimal domestic needs like water pressure and lights.


Option 2 - upgrade both alternators to 24V high-current
House 24V batteries charged from both 24V alternators with a shared external regulator, and topped up by solar. It would charge twice as fast as option 1, under 2 hours from empty to full.
Starter batts charged via 24/12 DC-DC from the 24V system

The alternator regulator is a single point of failure. If it fails, there's no electrical supply except a trickle from the solar, and we don't want to count on that.
The 24/12 DC-DC is also a single point of failure. Probably need to install or at least carry 2 as inability to recharge the starter is unacceptable. Depending on minimal running current draw, the 15A AC-powered trickle charger I use over the winter might do it via the inverter. A bit indirect, but an option.


Discussion

Naturally, the alternator vendor we're talking to favours option 2 - and makes the valid point that the percentage difference to all-in cost (alts, reg, batteries, inverters, wiring) isn't massive for superior charge capability. Equally obvious, though, budget favours option 1 by at least the cost of one alternator plus some supporting electronics/spares.

Option 1 comes out simpler and feels a bit more reliable especially for the major (engine-starting) concerns, though the fallback plan is less deluxe. With enough spending, option 2 can be made highly reliable as well. That might mean carrying an extra regulator ($$$) and DC-DC converter ($$) on board.

Option 2 faster charging is nice to have but not essential. Four hours from empty to full isn't that long to be underway. We would aim to discharge to well above 0% in any case. If the battery bank were larger, I'd think it more important to shorten the charge time. We'd be pushed in that direction if using air conditioning away from dock, or adding watermaker/laundry/etc which is a long way off if ever.

For our non-permanent-liveaboard lifestyle we are probably underway every couple days max, as we have places to go and things to see in a limited time span. That guarantees a certain amount of time charging. Ideally we'd never run the engines idle at anchor - not just for engine health but particularly because we've got smoky TMD41As. If we were going to do that, or if I thought we might be driven to it by insufficient underway time charging, it would argue for maximizing charging capacity (option 2) to minimize runtime.

Maybe it's relevant to reliability that the current 12V alternators are original 1987, while the new one(s) would be almost 40 years younger...

Basically either option looks acceptable. Option 1 is less expensive and perhaps a bit simpler. Option 2 is more capable and expandable, but spendier. In the end it seems to be dollars vs slightly faster charge times. Not sure if that alone is persuasive.

Expecting feedback along the lines of "option 1 is fine, save the cash to spend elsewhere and have fun cruising". Which does have its appeal for sure. There are always other uses for our finite cash with a boat.

I'm leaning towards option 1 but will fully cost out both options since they have slightly different electronics (FET isolator, DC-DC, reg, spare reg, etc)


Questions

• Did I miss anything?
• Any experience with external smart alternator regulators failing? It's all solid-state so should be highly reliable but nothing is 100%
• Any peripheral benefits? Alt upgrade would be a change from double-vee to serpentine which might be quieter and surely less messy
• Any issues with loading one engine 5-10% more than the other? Guesstimating 4 kWe (max rated) needs 8 kW mechanical at 50% efficiency, or 11hp on a 150 hp motor

Thanks for your thoughts

Jeff

 

[rslifkin]

Personally I'd want to keep things symmetrical between the engines. That's both for a little bit of OCD, but also for redundancy. If an engine is shut down for any reason I'd rather just lose 50% of my power production capacity, but not lose any functionality. Whereas if one engine charges the house bank and one charges the start batteries then an engine shutdown means one set of batteries is no longer being charged at all.

Depending on how much power you need you don't necessarily have to go crazy with huge alternators and regulators, but could go for something upgraded but still inexpensive. We have more solar than you do (and also have a generator if we need it), but we've been doing fine with our original 12V / 55A alternators. With DC-DC chargers feeding from them to the house bank I can harvest 750 - 800W (total between the 2) while cruising.

It might be an option to just put bigger internally regulated (inexpensive) alternators on the engines and use DC-DC chargers to feed power to the house bank from them. If you need more than 1200 - 1500W total from the pair of alternators then this option probably isn't a good one though.

 

[isophase]

If an engine is shut down for any reason I'd rather just lose 50% of my power production capacity, but not lose any functionality. Whereas if one engine charges the house bank and one charges the start batteries then an engine shutdown means one set of batteries is no longer being charged at all.

Heh, replied hastily and needed to edit. In the event of an engine shutdown I'd probably be more worried about the downed engine in terms of root cause - is the other about to go due to bad fuel or something like? - and maneuvering. DC electrical implications come later since batteries would have hours of runway left in terms of remaining charge. DC-DC options could make up the difference.

If it's alternator failure, can easily mitigate:
For the 12V, we'd keep the alternator that gets replaced as a spare.
On the 24V side, a 12-24 DC-DC could bridge the gap but with reduced capacity.

The dual-24V case actually seems a bit riskier since they share more (regulator, battery bank) and therefore have less redundancy.

I'd also love to hear some opinions on whether the engine balancing thing is actually "OCD" or a real issue.

 

[rslifkin]

The dual-24V case actually seems a bit riskier since they share more (regulator, battery bank) and therefore have less redundancy.

I'd also love to hear some opinions on whether the engine balancing thing is actually "OCD" or a real issue.

I'd want separate regulators for redundancy, not a single shared one.

As far as the engine load balancing thing, loading one engine more will cause higher fuel burn on that side and also slightly higher engine wear. And if you're talking about big enough alternators to potentially draw 10+ hp, you might want to knock an inch of pitch out of the props to avoid over-loading the engines relative to the designed prop curve. I wouldn't want to re-pitch props asymmetrically, so if you did both sides and only increase the load on one, then the other side is effectively under-propped.

 

[luna]

Have you confirmed that you can pull 11 hp off the front end of your engines?

Have you an alternator in mind?
Delco’s 40 SI is said to be 72% efficient. If so, the hp required to output 3.82 kW would drop to about 7.2.

I would also balance things out with one alternator & external regulator on each engine.
If they each output 2kW you could likely retain the double v belt drive and save the drive belt conversion costs.

I use double 5/8” v belts to drive my 2.5 & 2.9 kW alternators with no fuss or mess.

 

[Don L]

I feel that before you spend $$$$$$ you explain your boat use. The answer is a lot different between a "stay out on anchor for months and in same spot for 3-5 days and then motor 6-8 hours to next stop" and a "I stay out a night or two and then come back to a slip with shorepower"

I will say I full time cruised for 2 years with a 90A alternator, 390W solar, and 440 AH 12V house battery. So your 2x50A is already the same. If you do change to LFP it doesn't matter if you don't charge fully so you could make up a short trip later.

 

[SteveK]

I keyed in on this

• Lots of nights at anchor in inland waters of/near Great Lakes using primarily solar & battery

You have not said what Ah are needed for 24 hours at anchor. You did mention a high peak draw.
I would also convert both ALT to 24V with independent regulators with a DC2DC house to start. The twin 50A ALT with no GEN will take forever to charge planned house bank.
The 200W solar panels may serve to top up the start batteries, but not much help for a 24V 400Ah or 12V 800Ah house bank.
I do not see enough house bank size with no GEN is large enough for more than two days, followed by long runs to recharge. Maybe larger solar.

 

[O C Diver]

Option #3

Add a second alternator to one engine. Obviously it would be 24 VDC with the appropriate bank. Switch heavy users such as the inverter to 24 VDC.

Connect the two engine batteries with a high amperage switch. It would be normally off, but could be switched on to start an engine battery.

Whether you have a 12 VDC house bank tied to one engine battery or a seperate house bank charged off the 24 VDC bank with a DC to DC charger is your call.

On my single engine boat I added a second alternator. The second alternator charged the house bank. Only the engine and gauges ran off the engine battery. There was a switch to jump the engine off of the house bank as they were both 12 VDC.

If you want to see some pictures of the second alternator installed, there is an album of pics on my profile page.

Ted

 

[Insequent]

When repowering back in 2012 I ditched the stock alternators and installed 200A alts (12V) on each engine. There is a single external reg, a Balmar 612 Dual. I have had no charging issues at all in the 13 years of use.

More recently Balmar seem to be saying to use two regs, managed by their 'centerfielder', and that the Dual reg should only be used if both alternators are on the same engine. As I run both engines at the same rpm I dont see it as an issue. Over the years I have on a couple of occasions run one engine only for a few hours. I did not observe any reg or charging issues at those times.

My advice to the OP is go with option 2. Over time stuff will likely be added to the boat to improve liveability on the hook for extended times. Being able to get the house bank largely charged by a short hop to another anchorage is priceless. Do it in the morning and have your solar top the bank off.

 

[isophase]

Have you confirmed that you can pull 11 hp off the from end of your engines?

Nope. Any suggestions how I could do that? What would limit the power take-off? They are 1987 TMD41A Volvo. What I can say is that the boat is currently correctly propped +/- (WOT hits 3600 rpm as expected) with the 12V/50A alts on them.

Have you an alternator in mind?
Delco’s 40 SI is said to be 72% efficient. If so, the hp required to output 3.82 kW would drop to about 7.2.

I will inquire with the vendor. 50% was a total guess based on vague recollections of reading stuff. Hopefully these are better than that, so lower mechanical load.

I would also balance things out with one alternator & external regulator on each engine.
If they each output 2kW you could likely retain the double v belt drive and save the drive belt conversion costs.

I use double 5/8” v belts to drive my 2.5 & 2.9 kW alternators with no fuss or mess.

Good to know. I am relatively new to dealing with diesel engines in this level of detail. My engines have lots of belt dust stuck everywhere. As far as I know they are correctly tensioned, though no idea how often PO would have cleaned the engine. Seemingly not often.

 

[isophase]

I feel that before you spend $$$$$$ you explain your boat use. The answer is a lot different between a "stay out on anchor for months and in same spot for 3-5 days and then motor 6-8 hours to next stop" and a "I stay out a night or two and then come back to a slip with shorepower"

I will say I full time cruised for 2 years with a 90A alternator, 390W solar, and 440 AH 12V house battery. So your 2x50A is already the same. If you do change to LFP it doesn't matter if you don't charge fully so you could make up a short trip later.

It's between those extremes. Not being full-time live-aboards we are probably 1-3 nights somewhere and then a few hours between anchorages. Shore will be as infrequently as we can constrained mostly by pump-outs, and not necessarily staying the night. All the way empty to full would take 4 hours with one alternator so that seems pretty decent. If the battery bank were larger it would kind of mandate two alts.

The big difference from before in my mind is the induction stove. That's up to 3600W at peak, though it won't need full power for coffee, bacon, and eggs. I don't have good data on the average Wh/day we're likely to use.

 

[isophase]

I keyed in on this

You have not said what Ah are needed for 24 hours at anchor. You did mention a high peak draw.

I don't have good data on our average daily Wh draw. We were using CNG stove this season. When we bought in May the house batteries were in bad shape, no smart battery monitor, and the inverter cables were undersized so we couldn't do much with it so no data. Switching to induction and using the microwave more will increase it by a lot.

Planning to install a Cerbo so that will solve the "no data" problem.

I would also convert both ALT to 24V with independent regulators with a DC2DC house to start. The twin 50A ALT with no GEN will take forever to charge planned house bank.
The 200W solar panels may serve to top up the start batteries, but not much help for a 24V 400Ah or 12V 800Ah house bank.
I do not see enough house bank size with no GEN is large enough for more than two days, followed by long runs to recharge. Maybe larger solar.

Here "long runs" = 3h45 or so making 75% of rated capacity to charge from empty to full using one alt.

 

[luna]

Nope. Any suggestions how I could do that? What would limit the power take-off? They are 1987 TMD41A Volvo. What I can say is that the boat is currently correctly propped +/- (WOT hits 3600 rpm as expected) with the 12V/50A alts on them.



I will inquire with the vendor. 50% was a total guess based on vague recollections of reading stuff. Hopefully these are better than that, so lower mechanical load.



Good to know. I am relatively new to dealing with diesel engines in this level of detail. My engines have lots of belt dust stuck everywhere. As far as I know they are correctly tensioned, though no idea how often PO would have cleaned the engine. Seemingly not often.

I know next to nothing about your engines.

The power take off is normally limited by the ability of the bearings, seals or the shaft itself, for the idler, water pump(s) and crankshaft (plus anything else that is being driven) to withstand the eccentric loading. Volvo may provide some guidance on this issue, if you can ask the right person.

Good to hear that you make rated RPM with the stock 600 W alternators. Hopefully you do so with the higher output (2- 4 kW) units. I have my doubts if you settle on 4kW.
What manufacturer and model number of alternator(s) is the vender recommending?

Belt dust, if the belts are correctly tensioned is usually an indication that one or more of the driven pulleys is (are) out of 3 axis alignment. With a few measurement tools, a handful of 0.003" thick shims and the perseverance to get it right, usually the belt dust vanishes.

 

[isophase]

I know next to nothing about your engines.

The power take off is normally limited by the ability of the bearings, seals or the shaft itself, for the idler, water pump(s) and crankshaft (plus anything else that is being driven) to withstand the eccentric loading. Volvo may provide some guidance on this issue, if you can ask the right person.

I think I understand. So there's the torque necessary to drive the pump & alternator - that's the whole point of having the belt. More alternator power requires more torque. Then there's the belt tension which is required to keep the belt from slipping on the pulley, a "necessary evil". That would cause a force in the plane of rotation to be carried by the bearings. Since the pulley is sticking out from the engine it also puts a bending moment on the shaft. That bending moment and/or lateral load is the concern. Correct?

In this instance, the proposal is to switch from dual vee to serpentine. That should be able to transmit more torque for a given amount of belt tension. How much more, I don't know. It's up to 7x more electrical load. Maybe there are some efficiency gains so it could be more like 5x torque load. Then the advantage of serpentine belt would take that down somewhat (IDK how much?) by requiring less belt tension for the same load. ?

Good to hear that you make rated RPM with the stock 600 W alternators. Hopefully you do so with the higher output (2- 4 kW) units. I have my doubts if you settle on 4kW.
What manufacturer and model number of alternator(s) is the vender recommending?

Vendor is Electromaax. The product is: GenMaax Foot Mount, 24 Volt, 165A Alternator and Remote Rectifier - Electromaax . It would be paired with a smart regulator so I could limit power at various rpm. As I look into it that seems likely to be needed.

Belt dust, if the belts are correctly tensioned is usually an indication that one or more of the driven pulleys is (are) out of 3 axis alignment. With a few measurement tools, a handful of 0.003" thick shims and the perseverance to get it right, usually the belt dust vanishes.

That makes sense. I'm imagining a dial gauge mounted on the block to ensure drive pulley is parallel not wobbling, then a straight edge, a set of feeler gauges, and a fair bit of patience for the driven pulleys. Anything more complex than that? Or helpful tips?

 

[luna]

You seem to be on the right track, (remote rectifier, regulator and mutli V belt) to drive a substantial small case alternator.

The fitting of the mutli V belt conversion hardware is likely not difficult, nor complex but does require your "fair bit of patience". I expect that the original double V pulley is removed and the new pulley is installed in its place on the crankshaft.
While you are in there, you might want to consider replacement of the torsional damper (aka harmonic balancer) if it is near 40 years old.

Having the designer & manufacturer of all of parts required to complete this alternator upgrade right in your neighbourhood, is a big plus that is hard to ignore.

Good luck with the project

 

[CPD]

We also own a 37ft powered by twin TMD41As...and boat the same areas.
We went 140-Amp Alternators on both engines (de-tuned to 85 amps each to not stress them), upgraded to serpentine belts, an external Regulator for each Alternator (which intercommunicate for charging). Space is tight on the TMD41A, we went through 3 iterations redesigning the alternator mounts to fit the bigger alternators and align alternator pulley with the flywheel and waterpump.
Both engine alternators charge our LiFePO4 house bank. Engine start batteries charged via DC-to-DC from House bank. In 7 years we have limped home on one engine twice: once a one hour return (coolant leak) and the other a slow 3 day return (prop shaft separated from transmission). We have also had on occasion a Regulator act up until reset (it is a computer after all) - the 2nd Reg maintained proper charging. Twin engines/twin Regs have been a welcome redundancy.
We have a 9KW generator, but rarely use it after installing 800Watts of solar and a 2KW Inverter. We start the generator as often to simply exercise it as we do for AC power.
Largest draw is our refrigerator/freezer (near constant 24-hour draw of 8 amps through the heat of the summer - 2.5KW-hours each 24-hour period). Second largest draw is cooking dinner on the Induction stove top (~500 watt-hours which is about 10% of our House Bank capacity). Turning the fridge off at bedtime can extend our silent stay at anchor another night or two.
We rarely remain at anchor at one place more than 3 nights, and have found the solar returns us to 100% state of charge on a sunny day (~60% back to 100% by afternoon), and slows overall discharge on cloudy days such that our House doesn't descend to ~25% state of charge until after 2 or 3 nights requiring the generator or engines to re-charge.
While we made room for an additional 400Watts of solar - we don't need it. 800 watts of solar, sunshine, and our electrical usage provides us perpetual power in the summer. An engine or generator run every 3 days in poor summer weather restores us to 100%. We typically need to motor only 90 minutes to return to 100% state of change - a good number for the short trips within our home waters of the 1000 Islands.

 

[l00smarble]

I would lean toward option two with separate independent can-bus capable regulators but I’m just not seeing all the information I would need. You mentioned you’re keeping a 12 V system with a whole section of the panel for 12 V. Is there going to be a 12 V house bank? Separate from the two 12 V starting banks? Is this 12v house bank going to be lithium? Or AGM? What size?

Also, you really haven’t told us anything about the 12 V loads. Anything substantial?

Also, I might consider just doing too good quality 24 V alternators with conventional rectifier on board. I wouldn’t necessarily do two of those monster, externally, rectified, electro maxes. Yes, they’re good but if you’re gonna do both, maybe it’s a bit overkill and it’d be better to dial it back. Get the redundancy and easier installation cost and labor.

I have a feeling you’re holding back on doing a second alternator because you’re going bananas on the biggest most expensive 24 V alternator out there.

Also, I can’t remember if running their external rectifier, then locks you into using their alternator regulator, which I wouldn’t wanna do

 

[BB-marine]

I read your post and my take is your goal.

• Lots of nights at anchor in inland waters of/near Great Lakes using primarily solar & battery

Your approach is to increase your charging capacity of your engine alternators to do that along with a 24V LiFePO4 Victron 24V 400AH battery. Example (2) Victron 24V 200AH LiFePO4 batteries price out around $2900.00 ea. This will give you the equivalent of 800AH @12V. You are going to charge this bank mostly by engine alternator. So you feel that increasing the alternator output is the best way to approach this project.

You want to spend a lot of time anchoring but your plan is to run the engines/alternators every day to charge the large bank. (24V 400AH= 12V 800AH)

Your plan of increasing alternator charging is a good plan if you plan to move from an anchorage every other day or have a good power management plan. You did not state what your normal power usage is per hour running all electrical equipment on board. When you are done with your project it may work great but I think you are spending a lot of extra money that is not needed. IMO upgrading or repairing the 12V system that is installed should be first concentration. You indicated that it has given you a lot of grief. Read through the ABYC recommendations and start there. Think about adding more solar!

I had a 2002 34' Mainship. We did the Loop in this boat and cruised the waters that you intend on cruising in. We felt that section of the Loop was our favorite. We spent 2.5 months in Canada and Great Lakes during our loop and repeated the trip Canada, Trent, Georgian Bay, North Channel, Lake Huron, Green Bay, Lake Michigan twice . We have spent a total of three summers cruising in these waters.

The changes I made to make the boat suitable for this type of cruising in the summer time.
Alternators 55A: ( no upgrades ) twin 4LHA STP Yanmar

Starting batteries: (2) group 31 12V DP 650CC ea., 105AH per engine total (4) batteries

House and Thruster bank: designed for (2) Epoch 460AH 12V LiFePO4 batteries $2900.00 for both 920AH capacity.

Charging lithium batteries. (2) DC to DC Victron 12V 18A chargers one connected to port engine battery bank the other to starboard. Charging capacity from both engine alternators 36A per hour when engines were running above 1200 rpm. The key upgrade I did and recommend is Solar (put your upgrade money in solar)

I am quoting your goal "Lots of nights at anchor in inland waters of/near Great Lakes using primarily solar & battery " Solar and battery" " Not alternator and battery"

I installed 600W (3) 200 W panels with a 100V/50A Victron solar controller. Canada in the summer time gives you a lot of daylight and charging time with solar. This increases your time on the hook. You will be charging your bank at a rate of an average 25A per hour and maintaining all 12V users all day long. This may not work if you have a large boat with a lot of power demands but based on your description of your boat it seems to matche my use.

My 12 V power needs while at anchor.
24hour
12v refrigerator 5A = 60AH average
12V portable freezer 4A = 40 AH average
120V coffee maker to make pot of coffee in the morning = 25AH
Microwave/ convection oven 1hour use per day = 60AH
Hot water heater 6 gallon =70AH 30 minute per day
Misc. 12V users= 30Ah
House capacity 920AH usable 800AH daily usage average 300AH

Solar 600W will produce average 250AH in Canada durning the summer based on my experience . With this I have not started my engines. When we do pickup the anchor after 3 or 4 days on the hook. I will top the LiFePO4 batteries off to about 90% with an 8 hour run adding 36A per hour of run time. The great thing about LiFePO4 batteries. It is not recommended to fully charge them all the time. I do a full charge and balance them when we do go to a marina and provision. I use the 50A 120V shore power charger and let it charge the batteries while on shore power.

The complete install 3000W inverter, solar panels, Victron solar controller , Victron battery monitor, Victron Dc to DC chargers, Epoch 460 AH LiFePO4, 50A Victron 120V )Lithium charger,) 30A Victron 120V (lead acid battery charger) Lead acid Deka group 31 Dp batteries, fuses, breakers, battery switches, 4/000 cables, electrical connectors.... I invested about +/-$7500.00 in my install. I did all the labor and followed all ABYC recommendations. After the install I had a hull and mechanical survey done for insurance purposes and the ABYC and SAMS surveyor inspected the install and in his opinion it met the current ABYC recommendations. Below are some photos of this relatively simple install. Everything is BT and can be monitored with my phone or iPad.

My point of this, keep it simple. Concentrating on the engine charging system may get you the results you want if you plan on running the boat everyday. When you get to some of those anchorages in Georgian Bay and North channel, Lake Huron and Green Bay. The cool towns on the Trent you may not be starting the engine for a few days. You will want to stay!

My opinion, coming from a DIYer that has general knowledge of marine electrical installs. The sky is the limit now with all the latest greatest smart alternators and electronics. Converting an old school marine electrical system to a state of the art new technology system can be done but in the end it is costly and not needed if your needs are has simple as you described.

 

[isophase]

We also own a 37ft powered by twin TMD41As...and boat the same areas.

There's some saying about great minds...
We'll have to keep an eye out for you.

We went 140-Amp Alternators on both engines (de-tuned to 85 amps each to not stress them), upgraded to serpentine belts, an external Regulator for each Alternator (which intercommunicate for charging). Space is tight on the TMD41A, we went through 3 iterations redesigning the alternator mounts to fit the bigger alternators and align alternator pulley with the flywheel and waterpump.

Thankfully the vendor is handling that. They've been on the boat to check it out and are borrowing the hardware (alternator, bracket, and pulleys) to create the kit. Also the external rectifier really helps keep the case small to fit easily.

Both engine alternators charge our LiFePO4 house bank. Engine start batteries charged via DC-to-DC from House bank. In 7 years we have limped home on one engine twice: once a one hour return (coolant leak) and the other a slow 3 day return (prop shaft separated from transmission). We have also had on occasion a Regulator act up until reset (it is a computer after all) - the 2nd Reg maintained proper charging. Twin engines/twin Regs have been a welcome redundancy.
We have a 9KW generator, but rarely use it after installing 800Watts of solar and a 2KW Inverter. We start the generator as often to simply exercise it as we do for AC power.

Good data points to have. Vendor actually included a second reg in the kit which we will carry as a "cold spare". With that we have redundancy on pretty much every system.

Largest draw is our refrigerator/freezer (near constant 24-hour draw of 8 amps through the heat of the summer - 2.5KW-hours each 24-hour period). Second largest draw is cooking dinner on the Induction stove top (~500 watt-hours which is about 10% of our House Bank capacity). Turning the fridge off at bedtime can extend our silent stay at anchor another night or two.
We rarely remain at anchor at one place more than 3 nights, and have found the solar returns us to 100% state of charge on a sunny day (~60% back to 100% by afternoon), and slows overall discharge on cloudy days such that our House doesn't descend to ~25% state of charge until after 2 or 3 nights requiring the generator or engines to re-charge.
While we made room for an additional 400Watts of solar - we don't need it. 800 watts of solar, sunshine, and our electrical usage provides us perpetual power in the summer. An engine or generator run every 3 days in poor summer weather restores us to 100%. We typically need to motor only 90 minutes to return to 100% state of change - a good number for the short trips within our home waters of the 1000 Islands.

That sounds ideal to me. We're going for a similar house bank size (you said 500 Wh is 10% which suggests 5 kWh or so while we're doing 7). We don't have quite the same solar capacity so will probably have to run the engine a touch more often. There's no generator on board. No inclination to buy, pay for, install, run, or maintain one.