Fault Finding

After half a year of tinkering around with the 4.3l Volvo Penta petrol engines in Bandit, we haven't got very far in finding where our problems lie.

For the time we've had the boat, there has always been a rough, lumpy characteristic to the starboard engine at around 1000rpm. The issue is that on the river doing 4mph, we cruise at exactly this tick over speed. This lumpiness becomes irritating and uncomfortable after a while of cruising. We had originally thought it was the old carburettor coming to the end of its life. One empty wallet and a new carb later, we were left with exactly the same issues. As much as we tinkered around, this problem would not go away. We don't consider the two new carbs being a 'waste of money' because those old Rochester Quadrajets were 25 years old and the choke and vacuum were only just hanging on. We would have experienced issues with them down the line for sure. Best to just get rid of them and eliminate them as being a potential problem.

Dad decided to do the right thing and call up a mechanic to have a look and hopefully diagnose our issue. We usually like to fix these kinds of potentially expensive jobs ourselves but it seemed like on this occasion, we would have to get a professional's help as we are simply running out of ideas by this point.

The mechanic arrived at 10am this morning and quickly diagnosed that number 3 cylinder was not firing properly. We purchased a new spark plug hoping it was just a duff one but no luck. We have just replaced all the leads too so this can't be the problem either. The mechanic did look at the carbs, replacing gaskets and adjusting the idle mixture screws, just in case the carb was playing a role in our problem.

Final verdict: number 3 cylinder is not firing properly and there is no other way of going any further without removing the right-hand side head from the starboard engine. Dad reckons it could potentially be a leaky valve in which case, we would need to get it re-machined by a specialist. On the upside, we have been assured that the engines will remain in the boat. The pistons and piston rings are fine so there is no need to lift the engines from Bandit. Not only would this take a long time, but it would cost an absolute fortune. A fortune we don't have. We are more than capable of removing the head so this should keep final costs to a minimum.

We plan to do this work when Bandit comes out the water to have a bow thruster fitted during the summer. At least then we're not wasting any time while afloat. We'll just have to deal with a lumpy engine for the time being as we are still able to use that engine as we have done.

Definitely some research to be done...again.


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