QIf I suddenly pull the throttle back to tickover ( 800-900rpm) while travelling along, my 2009 Barrus Shanks 35 engine frequently stalls. What might cause this?
via the website TONY REPLIES... It could be overheating and suffering a partial seizure – but not if it stalls early in the day while the engine is not yet hot. Does it stall if you move it straight back to neutral? If not, perhaps the prop is too big, the stern gland badly overtight, the shaft badly bent, or engine alignment badly wrong. I would expect the gland to smoke in the last three cases.
If it stalls even when you go into neutral, it is likely to be an engine or fuel system fault. Does the injector pump have its own oil sump? If it is running dry or with fuel leaking into it from worn elements, that may be overloading the engine. Go through the
Afuel system to ensure the filter and tank are not contaminated with water or bug, the fuel liftpump has an adequate supply at idle, and there are no air leaks into the system. If you suspect a faulty liftpump, you could try fitting a Facet electric fuel pump – available from ASAP Supplies.
If your battery bank is well discharged, a large alternator can give this symptom – but it should clear as the batteries charge. You could increase the idle, but 800 to 900rpm indicates someone might have tried this – and it’s not good for a mechanical gearbox to increase it too much.
Might your rev counter be telling lies? Get a handheld one and check the reading: if it is reading high, calculate by how much, and re-set the idle speed to compensate for the error.
Finally, soundproofing (or rubber or foam to stop deck boards vibrating) can block the air inlets, starving the engine and leading to excessive engine room air temperature, both of which can cause stalling. To rule this out, wedge an engine cover up with small blocks of wood. If the fault disappears, add some ventilation.