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A major theme of this course has been to "get to know your boat and engine".

If you do not know how hard it is to turn your engine over with a big spanner, or if you do not know what it normally sounds like, you will not know when it starts to be abnormal.

It is nearly impossible to produce a single fault finding chart for all marine installations - this is my try.

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Is the stop lever on the pump in the stop position?

Is the fuel tap turned ON?

Do you actually have more than 2" (50mm) of fuel? – Check physically, try dipping the tank.

Check lift pump tell tale\breather for fuel leak.

Check that a fuel pipe has not been squashed (especially if they run along the engine bed which makes a good foot rest when working on the engine!)

Slacken injector pump bleed screw and pump priming pump – note what happens.

Pure fuel delivered with no air – injector pump problem, but check the breather and filters are clear before making expensive decisions.

Air or air bubbles in fuel – Blocked filter(s), Blocked strainer in tank, Blocked tank breather (may hiss if fuel filler removed as soon as engine stops), Air leak into suction line or lift pump.

Just air delivered – very bad air leak into suction line or lift pump.

No delivery – Very bad pipe, filter, or strainer blockage, Faulty lift pump.


Any form of blockage can be caused by water in the system so first check the lift pump chamber (because it is easy) and if that is clear open/drain the first filter like object after the tank.





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 confirmed by phone today (6/2/01) 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.


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.



There are so many variations possible it is very difficult to provide a single fault finding procedure, so I list some checks under the system types:-


Is sea inlet clear? Is sea inlet turned on?

Has something covered the sea inlet outside the hull?

Are any oil coolers clear?

Have any hoses collapsed or started to de-laminate?

Do you have any air leaks in the suction side – are the hose clips tight?

Is the raw water pump serviceable? – impeller faulty, body worn, cover loose or bowed.

If applicable is the raw water pump drive belt serviceable?

If applicable are any heat exchanger cores blocked?

If wet exhaust, is the exhaust fully or partially blocked? (Does it hiss more than usual?)



Check all above.

Does the engine have coolant in it?

Has a hose burst or started leaking?

Is the engine water pump serviceable?

Is the engine water pump drive belt serviceable?

Has an engine core plug or drain plug/tap failed?

Is your skin tank or keel cooler large enough?



Check all the above

Do you have a pressure cap?

Is the pressure cap serviceable?

Is the expansion tank large enough?



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