Belt tension is easy to adjust and can save a multitude of problems
Two weeks of gales punctuated the end of the summer holidays. Ferry companies transported the slightly damp and weary crews back to the UK leaving cruisers strewn in most channel ports.
The now balmy September allowed delivery crews to start the task of reuniting boats with their owners and toping up their tans. My little errand was a delivery from Amsterdam to Ipswich.
Arriving at the boat, the plan was to check it out that evening and set off early the next day. Whilst my crew had a look around on deck, I opened up the engine hatch.
It was evident there was a problem
My hands were black and so was every surface in the engine room. Black dust is a sure sign of belt wear. A loose belt rattles about on the pulley wheels; the friction creates dust which deposits itself all over the engine. The amount of dust indicated this had been problematic for some time.
The engine belt transfers power to different parts of the engine. On this boat, the belt was driven off the crankshaft pulley to turn the fresh water pump - so cooling the engine, then on to the alternator to supply charge to the batteries.
Common symptoms of a loose belt are overheating and reduced battery charging.
The first job was to clean up the dust because a clean engine is easy to visually check for problems. Engine cleaned, new belt in place and engine checks done I fired her up.
There was only just enough battery power to start her. The loose belt had affected the efficiency of the alternator so that it was not charging properly so I opted to leave her running for a while to put some charge back into the batteries.
A cloud of black smoke
Checking the springs would take the strain, I put her in-gear to load the engine and give it a good run. At about 1400 rpm I disappeared in a cloud of black smoke. It was obviously going to be one of those deliveries...
Black smoke can indicate a problem with the mixture of fuel and air. Lowering the revs and letting her run for a while the smoke colour changed back to normal. Because of the amount of dust I opted to look at the air filter first.
Engine off, I opened up the engine compartment once again and on inspection found the air filter thick with dust caused by the loose belt; slowly starving the engine of air. Duly cleaned, the engine ran much sweeter under load.
A peek in the logbook indicated a multitude of noted engine problems; battery charge warning light, engine running hot, black exhaust smoke. I’m sure they all stemmed from that belt.
Belt tension is easy to adjust and can save a multitude of problems. Look for the tell tale black dust or check the tension.
Types of belt
There are flat and V belts type belts. To check belt tension:
A ‘V’ type belt’s tension should allow you to deflect it by about 12mm. When correctly tensioned it should be just possible to twist a flat belt through 90 degrees.
Simon Jinks, RYA Instructor and Examiner
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