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High tick over engine

My vetus 3 cyl engine ticks over at 1500 rpm when book says 850 any idea why and how to lower revs, just bought boat and has been in marina for 12 months could it be water in fuel thanks

Asked by: Jim Bratt  | 6.54am, Tuesday 13 August

WW says:

There is an idle adjustment screw on the engine fuel pump. Often the screw comes loose- or (which is more likely) the throttle cable is too tight, not allowing the cable to run up against the stop, so preventing the idle speed from being normal.
You can download (free) the engine manual from the Vetus website; alternatively, ask one of the Vetus specialists, such as Kings Lock chandlery at Middlewich. If you have the original manual, it shows you how to adjust the idle speed- just make sure that you choose the correct screw! It might also be worth disconecting the throttle cable at the fuel pump, to see if the control moves back to the stop, and reduces the idling speed.
Another alternative is that the tachometer is not reading correctly- given problems with you other instruments, this could be a potential problem. At maximum power, does the engine reach 3600RPM or does it go off the scale? If it does, then it is liable that the rev counter is giving an incorrect reading. This could have several factors effecting it.
Water in fuel will tend to cause the engine to stop, as either the fuel filter will be blocked, or reduce the flow. If water makes its way into the fuel system, it is liable to damage the injectors and/or pump, as well as cause corrosion. Drain any water from the base of the fuel tank, and also from the rpimary fuel filters and engine fuel filter. If you are relying just on an engine fuel filter, I would strongly suggest that you fit a primary fuel filter (in the supply line, before the engine) at some point. The final engine fuel filter is not designed to cope with gross contamination of the fuel. However, this is not likely to be the cause of a high idling RPM

Mark Langley  | 10.47AM, Tuesday 13 August

I should add that if your engine is actually running at 1500RPM (which is a reasonable cruising speed for most narrowboats)then if you engage the gearbox at this speed, you are likely to do significant damage to the gearbox (particularly if it is a mechanically operated, rather than hydraulic box) and should be investigated immediately.
However, given your other problems, I think that it is probably unlikely that the engine is actually running that fast. You may want to use a marine engineer to check the systems over (and use a dial rev counter or timing light) to check the actual engine speed.

Mark Langley  | 10.51AM, Tuesday 13 August

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