I don’t have, and have never myself seen, an original description of the electrical system from LM yachts. Maybe someone else has one?
I shall try to describe the electrics of my own 1979 Mk1 LM 27, so far as I know it. I hope this may be of some help to you or others. Do let us know if you have any specific questions.
I will mark the things I believe are later (non-original) additions to my boat’s electrics with an asterisk, like so * .
Alternator - My LM27 has a Bukh 36 engine (most have Bukh 20s, or Volvos). The standard Paris-Rhone alternator on the engine has an integral electronic regulator mounted on it. (My regulator failed a while back, and was easily replaced.)
Charging System - I have a split-charging diode system (also Paris-Rhone, I think), which ensures both the engine and domestic batteries are charged by the alternator, but the batteries cannot discharge one to another. (A split-charging diode system is not ideal, as the diodes use a significant amount of power when the battery is much depleted, slowing charging when it is most needed. I intend to change this to a voltage sensitive relay (VSR) arrangement sometime.)
Batteries - These are secured on shelves either side of in front of the engine, under the aftermost part of the wheelhouse floor, engine battery to starboard, domestic battery to port. (My boat has also had a second domestic battery* added later, wired parallel to the first, and located under the forward part under the wheelhouse.) The batteries’ isolator (on/off) switches are mounted near the floor of the wheelhouse, below the wheelhouse seat.
Engine electrics - These are part of the standard Bukh wiring loom (detailed in Bukh manuals), and the starter motor and stop solenoid are key operated from the Bukh panel on the ‘dashboard’ of the wheelhouse. This is where the various gauges and and warning lights for the engine are also located.
Switch panel and fuses - This panel is on the upward facing shelf, to starboard of the wheelhouse seat. Mine has obviously been changed in recent years, so I don’t know what the original panel looked like or included. Mine now includes navigation lights (see below), navigation instruments, refrigerator*, domestic water pump, calorifier feed pump* (pumps engine cooling water through the calorifier), windscreen wiper. The switches on the panel are fused, and a few things that do not go through the switch panel (e.g. VHF radio) are fused by a small fuse panel in the little locker under the shelf just mentioned.
Navigation Lights - These are switched from the switch panel mentioned above. My boat has combined sidelights, a stern light, navigation masthead tri-colour light, masthead all-round white anchor light (this also serves as combined ‘steaming’ light & stern light, provided that the main stern light is covered or turned off while this masthead ‘stern’ light is used).
Navigation Instruments* - I have an echo sounder*, speed log*, chart plotter* and AIS receiver* all individually fused and connected together via the 'Navigation Instruments' switch and fuse on the switch panel mentioned above.
Domestic Lighting - On my boat there is no combined isolating switch for all the lights (as far as I am aware): they have individual switches on the lights themselves only. There is some sort of a distributor panel for the lights (and other wiring?) on the forward bulkhead of the hanging locker in the saloon (starboard aft). (Unfortunately my glasses do not allow me to focus close enough to be able for me to see this panel properly with my head in the locker, so I can’t provide any detail. I do not know if it contains any more than the lights.) I have two domestic lights aft in the saloon, and two forward, two in the forecabin, one in the heads compartment, and two in the wheelhouse (one added*, I think).
Heater (Eberspacher)* - This is (currently) wired directly from the domestic battery when connected (it should be fused, and I am in the process of changing this), and has a control switch in the wheelhouse, and a thermostat in the saloon.
Mains (230v) Voltage system (*?) - My boat has a few 230v continental type sockets around the boat (wheelhouse & saloon) connected to a shore power lead socket mounted in the aft of the cockpit. This installation looks very professional, so I do not know if this is original. (Could this be an LM ‘optional extra’? Would mains power on a boat like this have been normal in 1979?) This system has been extended at a later date by the addition of a few UK type mains sockets. (i believe the boat was originally kept in Denmark, and only came to the UK perhaps 25 years ago.)
Other non-original additions - 12v ‘cigar lighter ‘and 'DIN' sockets* for plugging in e.g. handheld VHF and phone chargers etc, and a bow thruster* (the most recent addition) are both connected to the 12v system. Mains (230v) powered battery charger*, which plugs into one of the existing mains sockets when the boat is connected to shore power.
Wish list - I have asked Santa Claus for a solar panel and a USB socket outlet!
Post by Brian & Glenda on Apr 30, 2021 7:32:04 GMT
I don't have an LM28, but believe that Jandane's original electrical diagram would be of interest to many LM owners! Could you post them to the forum please? Sula's description of his boat's electrics, very closely matches that of my LM32.
I have just started to investigate re-wiring our LM27 and was rather surprised to find that the wiring coming into the switch-fuse boards is solid, single-core copper, (about 1.5mm diameter copper). There are crimped spade fittings on the end of this solid wire to connect to the switches. Crimping solid core wire is generally frowned-on and my findings support that view. The wire is not at all well held in the crimped fittings. I'll probably keep the solid core wire where it is not subject to movement, but replace the crimp connectors with ones more suitable and secure for solid copper. Tinned "flex" with crimps will run from the secure solid-core connectors to join to switches where movement will be periodically needed.
My question is "Does anyone know if the original LM wiring was solid, single-core copper?" (Or has someone re-wired our boat with it?)
I have just completely rewired my LM27 and some of the original wiring was solid single core. This is completely inappropriate for a sailing boat so I have ripped it and all the other wiring out and completed a total rewire of the boat both mains and 12 volt circuits. I'm not an electrician but happy to pass on any limited knowledge that I may have accrued.....
I have some diagrams. No where is the quality of the wires stated. I will continue to look.The files are too big for uploading. If any of you wants them, send me a mail. jpschunck@gmail.com br. Jan
I have just completely rewired my LM27 and some of the original wiring was solid single core. This is completely inappropriate for a sailing boat so I have ripped it and all the other wiring out and completed a total rewire of the boat both mains and 12 volt circuits. I'm not an electrician but happy to pass on any limited knowledge that I may have accrued.....
Bob
I think saying it is 'completely inappropriate' is putting it a bit strongly. Yes, it is now considered poor practice - multi-strand wire copes better with vibration and being moved about - but it's been perfectly effective and serviceable in very many hundreds of LM27s for decades. (In the case of my LM27, for 43 years). I would be very surprised if there had been a significant number of failures of LM27 single core wires, and know for certain that there are very many things in an LM27 (or any other boat of that era) much more likely to go wrong.
Bear in mind, too, that not only have standards risen since the LM27s were built, but boats in those days had less in the way of both electrical kit and dependency on it.
It would be good to replace any single core wires with multi-strand if you are re-wiring anyway. If you're not rewiring or adding significant additional loads (where the adequacy of the thickness of the wire and size and quality of connectors is another and more important consideration), then don't worry about it - go sailing, or concentrate on more important maintenance and upgrades.
But if you have electrical problem, simply bear in mind the possibility of a broken solid core wire (not that multi-strand wire is immune to such problems, and has some of its own), but it's vastly more likely to be poor (broken, corroded, etc.) connections, or damaged insulation, than a broken single core wire.
(By way of background, long ago I used to do specialist electrical wiring for a living - wiring up safety-critical systems like railway signalling; and later doing quality control on the wiring of 'state of the art' tailor-made electronic equipment for aerospace (including space project), military, scientific research laboratories, etc. Such things were hand-built to VERY high standards of wiring (which, I'm sure, will have been raised further in the intervening years) which would be unfeasibly costly, and anyway inappropriate and unnecessary, for things like vehicles and boats.)
Thanks for the responses on the original wiring. I haven't found any signs of over-heating on the crimped connections that are loose, but I'm replacing them anyway. I've found that the live feed from the battery to the switch panel is black cable; presumably this is original wiring too. I've just replaced it with red having nearly reconnected the live directly to the battery negative. All good fun! Tony
I have 2 specific schematics of the LM-27, but they weigh more than 1 Mb and I can't attach them. And one of the LM-28 that is similar with only 300Kb the forum gives me an error when trying to upload it Error: This forum has exceeded its attachment space limit. Your file cannot be uploaded.
Give me a contact email and I'll send it to you .You can also find a lot of documentation in LMKlubbe web (subscription €25/year)
Thanks for the offer, Ulterius, but I don't think the original schematic would be of much use to me now. The wiring is a complete tangle with all the electrics that have been added since the was built. I'm just taking each wire and following it and then trying to see if I can't make things more logical and less haphazard. Putting all the negatives to one bus bar has "cleared the decks" a bit! Tony
Tonyp….That’s the way to do it. I did the same on my LM27 in 2007 and last year in my “new” LM28. Just start from an end, follow it and very often you will find that the wire has been disconnected from something and left in the boat. I got rid of several meters of not-connected wires. All other wires were inspected and renewed with soft core cobber where there were bends and possible vibrations. Other places where a wire connection was more firm (in a panel or so) I used solid core wires. Just do it and you will find out, it is not rocket science but rather simple and straight forward.
The best way to get to know your boat is by fiddling with it. I disassembled all the electrical part and I have gradually changed all the wiring, installing screened and fire-resistant cable for services, Ø70 mm hose for batteries and chargers, I have incorporated a 230VAC panel, 12 VCC panel with 24 individual circuits, new bilge pumps, galvanic isolator for grounding, AC-DC and DC-DC battery charger to be able to incorporate lithium phosphate batteries in the future.
If you are interested, next week I can incorporate some synoptic diagram. It takes time, but I believe that at this moment I can deal with most of the electrical faults that may arise on board
