How to trouble shoot your marine engine for a spring start.

Date posted: 27 March 2015

Most marine engines are reliable if maintained correctly, this blog article takes it as a given that you have winterised your  marine engine correctly.  Let’s take a look at what could possibly go wrong, if she fails to start in the spring.

labelled marine engine

Remember every engine is slightly different, but this will give you a general idea of where parts might be located (click on the image to enlarge)


1) Your engine will not start, although the starter motor is turning over.

The most likely suspects for this are,

A low battery, you will need to connect to the shore power and recharge your batteries fully (alternatively lug those batteries home to recharge – less than ideal!). Then check alternator belt tension. The engine harness fuse might be blown, replace fuse (located by starter motor or above flywheel housing) and check for wiring faults. Check to make sure that the power is turned to engine battery and not auxiliary (as this may be too low to kick start the engine after the winter).

No fuel; or air in the fuel system, or a blocked fuel pipe, water in the fuel, dirty fuel filters, fuel lift pump seized, blocked injector, fuel turned off, heating elements (plugs) not working. Ideally you will need to work through these issues if you believe it might be fuel led. I would suggest check your fuel levels and turn the fuel cock on to start with. Vent the air, check the air intake filter every season and changed every 2 years or if clogged. Change the fuel filter, remembering to put some oil round the seal before tightening and bleed. Check the plugs are clean and replace if they are burnt out, check the wiring to the plugs. Check the solenoid is free to return to the run position.

2) Erratic Running.

I had rather a scary incident with erratic running myself and it transpired that the engine fitted in the previous year did not have the exhaust fitted in a high enough position, and salt water was running back into the engine when we keeled.

I hope it’s nothing that awful let’s look at what other problems might have arisen.

You may have air in the fuel supply, so you will need to check supply system pipes for leaks and fix.

The Fuel lift pump may be faulty; if it’s not flowing freely, the easiest option is to replace it, it is a really simply procedure.

If your fuel filter is clogged, I would want to know why, check to make sure you don’t have the fuel bug…. Replace the fuel filter.

Or the fuel return is not fed back to the fuel tank, or blocked pipe, this will be a matter of re-routing the pipe or cleanly the pipe thoroughly.

If it’s a faulty stop solenoid, simply disconnect wiring to solenoid then if running improves check for a wiring fault.

Check your air filter to make sure it is not blocked; this should be replaced as a matter of course when you service or have serviced your engine.

Worn or blocked injector, this is a simple one to remedy, the engine must be running at 850 rpm in gear, anything less is too low, so just increase your revs and tick over speed.

Broken fuel injection pump spring, the only thing you can do is replace it.

 3) White or blue exhaust gas

Initially check that the engine oil level isn’t too high, if it is showing too high on the dip stick, open the drain whole underneath the engine and remove some of the oil.

White smoke will also appear if you have a blocked injector, this is an easy one to solve, just service your injectors.

Not such an easy issue would be if your piston ring and bore are worn, which would the give a low compression. You can check this by removing the rocker cover and lowering and raising the pistons, checking the shaft and the piston as you do, to look for signs of wear and dare I say rust. If you aren’t familiar with this procedure, best to contact your dealer, as you are entering the realms of expensive work!

It sounds basic but check that the breather pipe is clear and unobstructed.

4) Low oil pressure warning comes on when engine speed reduced to tick over.

Firstly check your oil filter, this may be blocked and need replacing.

There could be insufficient oil, if you topped up at your last service; check for leaks in the bilges.

The engine may be running too hot, check the cooling water flow.

Clean the oil relief valve which could be dirty, meaning it doesn’t close properly.

At the very least, check your wiring and the ‘switch sender’ for any faults.

5) Overheating engine

Top up the coolant level

Check the sea water inlet and clean the filter, make sure there is sufficient sea water flow, is the sea cock open?

The zinc anodes may have degraded, flaking and blocking the tube stack, you will need to remove and clean the tube stack thoroughly.

Vent air locks in cooling pipe to keel cooler, and top up coolant.

Check your impeller for signs of wear and replace if necessary.

Here are some links to further instruction manuals for marine engines, if you have any additional links to further instruction manuals please add them in the comments.






Stuart Turner:


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