Boat Fault Finding - Marine Electrical Problems

Finding canal boat faults - marine electrical faults.

Fault Finding

Tony Brooks is an expert on Marine Diesel Engine & Boat Maintenance matters. Thanks to him and TB-Training for permission to reproduce these materials.

 We've got Faultfinding Checklists and over 150 answers to problems in the sections listed far right.

If you have a canalboat problem.

Tony may answer, time permitting, your problems concerning UK canalboat mechanical and electrical issues - Tony cannot answer questions about sea-going or overseas craft. Give him plenty of details about the problem, its background and your equipment. And don't be too impatient, remember this is a FREE service! Contact him via his website.
CANALBOAT FAULTS
General Problems
Electrical Problems
Propulsion Problems
Engine Problems
Cooling Problems
Smoke Problems
Faultfinding advice
ELECTRICAL FAULTFINDING CHECKLIST
STARTER\BATTERY FAULTFINDING BATTERY TESTING STARTER CIRCUIT TESTING
All readings assume a 12volt system – double for 24 volts
Clip a volt meter across the battery terminals and take the following actions:-
Take a reading immediately:
More than 12 volts = battery PROBABLY OK – higher the better up to 13.2 volts
Less than 12 volts = battery PROBABLY flat or faulty – see battery checking below.
Get someone to hold the stop control in the stop position. Spin the engine on the starter and after about a second note the reading.
10 volts and above = probably a starter fault if the engine is not spinning as normal. (I would accept 9.8 volts).
Less than 10 volts = starter, battery, or seized engine fault.
Assuming the engine can be started. Run engine at a good speed (say 1500 to 2000 rpm) and watch the voltmeter. It will probably read 13 volts plus, but watch for a while and see if it starts to creep up, if it does wait until it stops before taking a reading.
13.8 to 14.2 volts (plus or minus about 0.2 depending on make) = alternator PROBABLY satisfactory.
Less than 13.8 = faulty battery or alternator (Check/rectify battery BEFORE condemning the alternator!
More than 14.2 volts = Charge controller in use or faulty alternator voltage regulator.
Testing the alternator for more reliable results requires the use of a high current ammeter – you drop a lead and you will probably set fire to your wiring, so it is beyond the scope of this course.
EXIDE UK informed us that there are no end user tests for Gel or "sealed for life" batteries. They stated that the batteries must be taken to a battery specialist for testing.
Testing "Normal" lead acid batteries.
ACID IS DANGEROUS – TAKE GREAT CARE
Make sure that battery has sufficient acid in all cells to take hydrometer readings.
If not, top up and charge for several hours – then let the battery stand to cool.
Note the following:-
Colour of the acid – if one or more cells are brown the battery is probably at or very close to the end of its life.
The actual reading from each cell – a difference of more than 0.05 indicates a faulty cell (but I would charge it and recheck before condemning it).
The state of charge (on the opposite side of float to the numbers).
More than half charged = probable faulty starter.
Less than half charged = slow charge at 1/10th of the battery’s amp hour capacity (or less), taking hydrometer readings every hour. When they stop rising over two consecutive hours the battery is charged.
If the case or top looks as if it is swelling up, you can be sure the battery is at or close to, the end of its life.
Do not start this unless you are confident in your use of a voltmeter, you can again cause a fire or get burnt!
All tests assume negative connection to starter case or engine and pre-engage starter (with the solenoid as part of the starter) 
Ensure the battery is serviceable and sufficiently charged.
Connect voltmeter across battery, operate stop control, spin engine on starter and take reading. This is your "base" reading.
Less than 10 volts = faulty starter or seized engine.
Leave negative connection on battery, connect positive to main, battery, terminal on starter (the bolt connection farthest away from the starter body). Operate starter and take reading.
More than about 0.5 volts less than "base" reading indicates faulty connection between battery & main terminal.
Move pos. connection to other big terminal, operate starter.
More than 0.5 volts less than in 3 above = faulty starter solenoid.
Move positive connection to starter body, operate starter.
More than 0.25 (I say 0.5) volt reading when starter is operating shows a bad connection in the negative circuit back to the battery.
BATTERIES LOSING CHARGE FASTER THAN RECHARGING
 Apart from the fridge and seldom the TV the 240v circuit is not used much but the service batteries are loosing their charge faster than the engine alternator can replace the charge. The result is a dead 240v circuit and failure of the Ebersbacher heating system.  Click to see answer
12 VOLTS ON HULL
I have recently discovered that I have 12 volts flowing through the hull of a 40 ft narrow boat, even when the isolator is turned off, which has caused bad pitting. Where is this 12v likely to be coming from and is it worth putting another isolator on the other side? Click to see answer
WHAT SORT OF CHARGING SYSTEM DO I HAVE?
I have just purchased a fairly old (1986) and basic 60ft narrow boat. It has 2 domestic batteries and 1 starter battery. The boat was described as "split charging". What are the simple steps I should follow to understand what charging system I have ... Click to see answer
GAUGES READ BACKWARDS
The fuel gauge reads empty when full and full when empty, also the oil pressure gauge needle goes down when the engine is revved... Click to see answer
RELAYS ON NARROWBOATS
Being new to Narrowboat Electrics (familiar with car electrics) I find it strange that there is no mention of using relays in the circuits. Any reason for this? Click to see answer
STARTING PROBLEM
I have an electrical problem with my parsons engine. I stopped the engine when I went to restart it just wouldn't turn over and when I turned the ignition it just clicks. the clicking seems to come from a solenoid between the ignition and the starter motor. Click to see answer
FITTING SHUNT AMMETER
I am a bit confused about how to connect up my new amp hour meter to my narrowboat's electrical system. I want to measure current into and out at the battery bank. I have read your reply to a previous enquiry about adding a shunt ammeter, but I am still a bit lost. Click to see answer
BATTERY USAGE CALCULATION
We found that when we came to switch the TV on (a 10" CRT colour portable) it would quite often not switch on unless I started the engine. Do you agree with the load calcalations I've done? Click to see answer
ALTERNATOR PROBLEM
I have a BMC 1.5 engine with two alternators, mounted one above the other. One of the alternators (Lucas ACR25 I think) has stopped charging. Can you advise what alternator I can get that will be a straight swap.  Click to see answer
NARROWBOAT BATTERY CAPACITIES
I have a 60ft narrowboat which I am just about to move onto permanently. I currently have 5 batteries a 110Ah heavy duty starter battery (new) and 4 x 110Ah leisure batteries connected together for the domestic power. Could I reduce the domestics to 90Ah units ?  Click to see answer
FUSE RATINGS
I have just had a pre-inspection of my boat for the BSS, to identify what needs to be done to make it compliant, and the examiner has advised that the fuse ratings of the fusebox be checked and rectified as necessary, but I am not sure how to do this, can you help?  Click to see answer
NARROWBOAT FRIDGE
I have 240v/12v/gas fridge which is currently only connected to the 240v. It would be far easier to wire it to 12v rather than connect the gas which due to the positioning etc would be a little awkward.  Click to see answer
TWO BATTERY SYSTEM
I have two batteries on my boat one for the engine ,one for lights and power ,how do I connect them , I have one battery isolator that can isolate one or two batteries or both, do I need to run the -ve on their own or can I link the two batteries together.  Click to see answer
SOLAR POWER
Assuming the bulk charging will be done either from the mains charger or from the alternator(s) if we're cruising, we'd like to connect a third source, e.g. solar, to provide a float charge while the boat's unattended..  Click to see answer
FAULTY YAMAHA FUEL GAUGE
I have a Yamaha Fuel gauge which I have no power to the sending unit lead wire (red).  Click to see answer
ALTERNATOR WIRING
I have purchased a 58 ft sail away, it has an Isuzu engine with 2 alternators, one is connected to the engine service battery. Can you tell me how to connect the second 70 amp alternator to the domestic batteries.  Click to see answer
WIRING FOR TWIN ALTERNATORS
I have a 1.5 BMC with a second alternator fitted I bought the boat with this fitted but it was not connected up the boat was wired with a battery selector switch (guest) only using 1 alternator. Click to see answer
CONNECTING BATTERY BANK TO INVERTER
I want to use a separate bank of two 110 amp batteries, solely to power an inverter, but do not know how to connect them together in "parallel" to give me 220amps.How do I do this? Click to see answer
TACHOMETER CONNECTIONS
We want to know what revs the engine is doing and VDO can supply a 24v tachometer which can be connected to the alternator for diesel engines.  Click to see answer
DUTCH BARGE ELECTRICAL SYSTEMS
I am the proud owner of a little 1923 Dutch barge. The pre-purchase survey that was conducted, reported that both the 240V AC and 12V DC circuits were "DANGEROUS". To this end, we employed an old shipwright to correct the problems.  Click to see answer
CHARGER CONNECTION
I have a narrowboat that has one starter battery and two leisure batteries, all Elecsol 110 with a split diode. To separate the two banks. How do I connect the charger? It only as one positive and a negative terminal on the DC output side. Click to see answer
FREQUENCY CONVERTERS
We have recently installed a domestic full size dishwasher on a vessel which has a 60 hertz frequency! The problem is that the dishwasher is rated to operate on a 50 hertz frequency and is malfunctioning on the current source. Click to see answer
CHARGE SPLITTING RELAY
I have had had three Charge Splitting Diodes fail on me over the past few weeks, and he only advice I received from the diode manufacturer when the third 70 amp diode blew was to fit 90amp (or higher rated) diode.  Click to see answer
INVERTER AND EXTRA BATTERIES
My boat is fitted 1 aux & 2 leisure batteries I want to fit an inverter and have plans to run it from a different set of batteries (2x110amp). Click to see answer
ADDING FIELD WIRE TO BMS
I have acquired an Adverc battery management system but cannot find a field wire on the alternator. Click to see answer
BURNT OUT SPLIT CHARGE RELAY
I have had 2 Lucas Split charge relays (SRB630) burn out in rapid succession. The set up I have is a Yanmar 27hp engine with a starter battery and a 150 AH "Leisure Battery".  Click to see answer
BATTERY PROBLEM
I know nothing about engines.......my boat has been in storage I hooked up the battery and all I get is a click when I try to start. Any ideas before I take it to the shop? Click to see answer
ELECTRICAL GREMLINS
I turn on one circuit breaker and voltage ranging from 1.5 to 12.5 volts is sent to five other circuits. Other circuits besides these six work normally but these six don't work at all--no amps flow and no users work. Click to see answer
LUCAS ALTERNATOR PROBLEM
Every time I turn the boat on the ammeter light stays on. The alternator has been tested and is all working fine. Do you have any ideas what would cause the light to stay on permanently?  Click to see answer
FITTING ADDITIONAL ALTERNATOR
I am refurbishing a narrow boat and am trying to find details for attaching an additional alternator to the existing Perkins engine. Click to see answer
TOPPING UP MODERN 'WET' BATTERY
How do I top up a modern "wet" battery?  ...  Click to see answer
REWIRING A CANALBOAT
I am an electrician who has been asked to wire up a canal boat, as this boat is to be docked they wish it to be wired to a 240 volt system which will be connected to an r.c.d landside Click to see answer
RUNNING A PLAYSTATION ONBOARD
To provide an alternative means of entertainment for my two young children, whilst we are cruising I was contemplating bringing the Sony Playstation 2 onto the boat. Do you think my 3 x 110 amp domestic batteries will cope? Click to see answer
FITTING FRIDGE VENT
I have recently purchased a small Electrolux 3 way fridge, its condition is very good ,can I fabricate a vent for the fridge myself or will I have to purchase one Click to see answer
INVERTER AND BATTERY CAPACITY
I have a narrowboat with three 90ahr leisure batteries fitted and would like to fit an inverter. What I would like to know is, would the battery bank be sufficient to use, say an 1800w modified wave sterling model. Click to see answer
ELECTRICAL SYSTEM RECOMMENDATION
Maybe you can make some suggestion for my new narrowboat purchase. The electronics leaves a lot to be desired. So what would you suggest I need to do to end up with a functional electrical system (apart from the obvious fusebox to separate my boat from the National grid!!!) Click to see answer
BOAT ELECTRICS
Dear Tony, I am new to boating. I have been on holiday on a narrow boat before, but I am now about to purchase one. I don't  have any problems regarding the handling of a boat. However I would like to know about boat electrics. Could you explain ....  Click to see answer.
ELECTRICAL PROBLEM
I have two alternators on my engine and the domestic batteries are flat. The warning light for that alternator does not work because its terminals keep falling off and its ammeter does not show a charge. (light uses lucar blade terminals) Click to see answer.
ELECTRICAL FAILURE
When I try to run any 'major electrics', such as pushing 'up or down trim' to raise/lower the drive or trying to start the engine, I hear a sound like the 'click' of a relay, and then everything dies  ...  Click to see answer
ELECTRIC FRIDGE
I want to install a 3 way fridge, am nervous about using gas, and would prefer to power it on 12 volts. However I expect this will drain the batteries very quickly.  ...  Click to see answer
WIRING DIAGRAM FOR BMC
Could you please tell me where to obtain a wiring diagram for a 2.2 BMC. While making a new control panel I did not make a good enough job of marking the old wires. ...  Click to see answer
EARTHING TO HULL
I have read in a book that in addition to the 2 wires system the negative of the battery should be earthed to the steel hull, is this correct? and if so why. ...  Click to see answer
REPLACING ALTERNATOR
I had to exchange my original 11ac alternator with a new one - Lucas looking quite alike - featuring one less terminal. ...  Click to see answer
WIRING A CONTROL PANEL
I have a BMC 1.5 marinised diesel engine, an ammeter, an oil pressure gauge, a tacho, a temp gauge and a 4 pos key switch (inc off ). Can you suggest a wiring diagram for the control panel to the engine and it's components? Click to see answer
ADDING AMMETER
l have twin Perkins 4 108's,the port engine has 2 120 batteries to run lights, heating fan, and extras, l charge them up often with the engine, only a voltmeter to give an idea of state so l would like an ammeter to show when l am no longer charging off the engine. ...  Click to see answer
SHOWER PUMP FUSING
I have installed a shower into my narrowboat and connected all the plumbing etc. I assumed I could take a link from the lighting circuit to power the pump-out pump, with a separate switch and in line fuse. I found this kept blowing the light circuit fuses. ...  Click to see answer
STERLING ALTERNATOR MANAGEMENT SYSTEM (1)
I have a 56ft narrowboat, 12 months old. What I would like to know is if I fit the above battery management system, I am told that it will cook the batteries and they will eventually fail. Is this good advice ???? The one I am thinking of fitting is the new digital model which has a temp sensor fitted. ...  Click to see answer
STERLING ALTERNATOR MANAGEMENT SYSTEM (2)
I have been almost persuaded .. to buy a Sterling advanced alternator regulator. (I realise you prefer Adverc but price is nearer my limits!) I am fitting a 70 amp alternator and will have two leisure and one engine battery. Do I need a split charging/blocking diode as well?. ...  Click to see answer
RECHARGING NARROWBOAT BATTERIES
Being new to narrowboating, I wasn't aware how regularly I need to run the engine to recharge the batteries on my boat - subsequently they are now too low to be recharged from the alternator. Following advice from a fellow boater, I have disconnected the batteries and brought them home for recharging. This is where I get muddled. ... Click to see answer


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