I’m no marine mechanic, but I’m a boat owner who has seen some of the things that can spoil a day on the water. It’s something nearly every boat owner experiences sometime. The boat is humming along quite well and then suddenly, there’s no sound from the engine, or it revs really high and the craft isn’t moving. It’s running rough and can’t seem to snap out of it. None of these scenarios are what boaters want, but things happen. A few thoughts on the topic won’t go astray.
Most small craft are outboard powered, so we’ll stick primarily with these engines. Remember, this is about trouble shooting first – if a total engine failure occurs, there’s not much to do except organize a tow home. Membership with the Volunteer Marine Rescue is a great safeguard, as this facility not only assists with breakdowns but can help with tows off sand banks and many other marine issues.
With smaller engines hooked up to a tote tank of fuel, we could rightly regard fuel supply problems as a prime suspect for many stoppages. I once saw the in-tank pick up pipe that sucks fuel from the tank and up to the main fuel line connections fall off the metal fitting into the bottom of the tank, on a brand new fuel tank. This meant that the engine would start when fuel was slopping around in the near full tank and run for a few seconds before stopping again. It was frustrating and took time to find – an extremely rare occurrence.
If the boat suddenly stops after running a bit ragged for a few seconds, and then refuses to start, fuel issues should be a primary suspect. Take a look at the fuel tank and see if the breather on the cap has been opened or if the cap has been loosened a turn from when the tank was last filled. Boaters often remove their fuel tank from the boat and fill it at the local service station, after which the cap is given some serious tightening to prevent nasty petrol smells escaping in the car. I’ve done this myself.
Another fuel issue comes from the click-on connection between the fuel line and tank coming undone, which they sometimes do. This can be rectified. A couple pumps on the fuel primer bulb will often get things moving again. All fuel line connections that are accessible are also worth scrutinising. Cheap factory clips can come loose, connections come asunder, the primer bulb can split (a band-aid will fix it) and all these situations can let air into the fuel line to interfere with engine suction. If a dodgy clip is diagnosed, sometimes merely cutting off a small bit of fuel line and reconnecting a tighter section via the clip will keep things going well enough to get home.
Be advised before powering off, once a fuel issue is solved and the engine fires up, a fuel injected engine should be given time to idle for a while until it’s running smoothly. Full fuel flow needs to be resumed or the engine will struggle to run evenly under load, simply because the engine computer needs to be satisfied that all’s well, including fuel flow. An older style two-stroke won’t suffer from this short delay – with fuel in the cylinders it’s ready and willing to go.
Outboard engines come with emergency cut out switches – the kill switch. It’s important to ensure that the switch is engaged correctly on the tiller arm, or up near the forward controls where these are installed, otherwise the engine will never start whether it’s a key start or pull start model.
If a pull start engine won’t fire up after apparently running well, and fuel tank cap or lines are eliminated as the problem, I’d be casting hard looks at that kill switch. The trouble is, without some electrical knowledge, not much can be done on the water, apart from disconnecting and reconnecting the switch into it’s clip, to try to overcome or bypass a possibly bad electrical contact. Incidentally, the latter tactic is worth trying.
Electrical issues can occur in both small and large engines. One of the most common is a total battery failure. Any boat battery can fail after a few years of sitting in a boat, so it’s wise to have the battery load tested from time to time to assess its health. Even a good battery can drop it’s bundle. A canny boat owner will be grateful for the alternative pull start system the engine has, or will have read the service book that came with the engine and know exactly how to get a rope onto the engine’s fly wheel to give it a pull start.
I saw a mate start a 90hp outboard with a rope while we were a long way off the Gold Coast. He knew which parts of the shroud around the flywheel to remove, had the tools aboard to do it and he did it at home as an exercise. He was confident in the whole procedure.
Another culprit for electrical failure is the good old battery isolator switch, if fitted. These items are not bulletproof and if one’s subjected to spray or is located in a place where it can be damp for a fair time, maybe in an enclosed hatch, it can easily short out and stop the engine. Worse, it can fry the engine computer. Maintain your VMR membership as the engine sure won’t be starting again that day.
If the isolator switch has dropped its bundle, it’s likely that all electronics can drop out as well, because power won’t be exiting the battery. Have the phone aboard to ring VMR. In truth, electrical problems from isolator switches are a lot more common than is generally understood. Replace the unit every couple of years if it’s in a place where salt water or salt spray can get near it.
Let’s take another scenario: the boat has been running well but there was a brush with a sand bank or two recently, or contact with stumps up the top of that lovely dam where the bass and goldens were on the boil. Suddenly the engine is revving quite well, but the boat isn’t moving forward.
Outboard engines have a rubber bush in the propeller to avoid hard jarring when gears are engaged, and to act as a primary shock absorber for the gearbox when hard objects are hit. This rubber bushing can totally chew out over time or with sustained impacts. The result will be a total loss of propulsion under hard power, but sometimes a very gentle application of throttle can get the boat moving again. It depends on how badly the bushing is damaged. If all propulsion is lost, it’s time for a tow.
Your outboard might have overheating problems. While these incidents can occur as the result of water pump impeller failure – a lack of proper water service – a more likely incident will involve an obstruction over the engine’s water inlet. If the flow of water from the engine is steaming just before the engine shuts down, lift the outboard and check for a plastic bag or other debris around the inlet area. Fortunately, many of today’s high end engines are designed to detect overheating and respond by shutting down to prevent seizure. If an obstruction is found, give the engine fifteen minutes to cool and try a restart.
This describes an engine that is misfiring badly, running rough, or seems to be trying to stop but not quite doing so. This can be a difficult situation to diagnose out on the water, but is often attributed to fuel filter issues. The only option is to keep the engine going – so long as there are no overheat alarms present. Don’t push things too hard, just sneak back to base as quietly and efficiently as possible.
Find what revs the engine wants to run at and stay with that one throttle setting. The fuel filter will usually be a job for a marine mechanic unless it’s conveniently located – some certainly aren’t. If the boat can get back to the ramp, the day ends alright.
Those are a few first response scenarios, and I sincerely hope that you don’t have to refer to any of them. All else failing, it’s time to call VMR – you can join on the spot if you’re not a member. Get the Vee sheet out to advise other boats that you’re not able to proceed.Reads: 163