Colin Staple is having trouble sailing because of his unreliable outboard. Stu Davies explains how to improve it.
With over 70 years of small outboard experience from the reliable Seagull to modern leading brands, I’d like to know others’ views on modern small unreliable outboards; problems seem to be allegedly connected to present day petrol containing blends of ethanol.
I cannot understand why they don’t seem to be as reliable as lawn mower engines which are usually much less looked after.
After use, the 2.5hp engine used in the tender is flushed with fresh water and the carburettor runs dry.
Colin Staples laments that modern engines don’t seem to be as reliable as his old Seagull outboard. Credit: Paul Andreassen/Alamy
As recommended by our supplier, the 5hp motor is mounted on the transom. It is then run down after each use.
It can result in stuck floats, jammed needles, and blocked jets if the system is not drained.
We’ve tried long-life petrol without ethanol at £26 for 5lt but this still gives problems.
The latest advice I have received is not to drain the engine if using it next week, but do drain it if you’ll not be using it for a longer period.
Occasionally, after the engine has started and been running okay, it won’t restart.
This outboard is a disaster. It was fine 70 years ago to sail up the Hamble and pick up a mooring, but today with all the activity it’s a bit risky.
Colin Staples
Stu Davies responds:
Here, there are a number of issues. Block jets and stuck-on valves. There is also a reference to ‘running dry’.
I’ll start by covering 2-stroke engines first.
Let’s go through the ethanol issues. Ethanol is attracted to water and water then appears in the fuel. (Think whisky!) This is a mixture between alcohol and water, with a few flavourings.
If you leave your engine over the winter with a liquid in the float, water will remain in the bottom to react with metals within the carburettor.
It’s this water and its by-products that hang around in the float bowl that can lead to the blocking of orifices.
I’ve seen a float bowl almost full of aluminium oxide caused by this!
To a certain degree the ethanol petrol in my small garden 2-stroke engine ‘melts the fuel lines and components.
These problems could be caused by a plastic residue.
Running the engine dry doesn’t completely empty the float bowl and any water droplets in that float bowl full of fuel will be left there; water is heavier than fuel so all the water in it will be left there if it is just ‘run dry’.
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With sticking valves, again, just ‘running dry’ allows some mix to remain in the float bowl; the fuel evaporates leaving a mix of oil and water behind.
The oil can become sticky. The oil becomes sticky and can cause float-shut off needles (stuck) to stick.
Aspen Alkylate is supposed negate the effects of ethanol so that should be able to sort it out.
Why are you still experiencing problems with it?
For 4-stroke engines all of the above is still applicable regarding water in fuel.
The carburettor jets and orifices are smaller in 4-strokes, and therefore more susceptible to blockage.
So if you’re going to empty the carburettors, empty them properly – open that drain screw in the bottom of the float chamber.
It’s a 2.2hp Mercury 2 stroke outboard with a cover. It sits there for months.
I was away from home for a considerable time during the Covid-19 pandemic.
It was easy to start after six months with the old fuel that had been left in it.
This season I didn’t bother, I just left it for a month; it fired up quickly but then died.
I stripped the carburettor and found a hair in the float valve – the cause of it sticking closed.
The fuel may react differently in Portugal due to the higher temperatures.
Drain the fuel from an engine if you are going to leave it for a while. Use fresh fuel on a 4-stroke engine.
Even in simple engines, fuel systems are now a common maintenance item.
Electric outboard anybody?
Enjoy reading Why is the outboard on my boat so unreliable?
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