Hi,

My outboard had some issues where it wouldn't run very well - would kind of idle roughly, but any throttle and it would die. Its a two stroke 6hp. I cleaned out the carby a couple of times and it seemed to improve, but then decided not to start at all. After doing everything I could think of I took it in to the mechanic to have a go.

He did the obvious things - cleaned the carby, changed the plug, did a compression test - but also failed to get it to start. Then he put a boroscope in to the cylinder and claims to have found two holes caused by corrosion. He can't confirm if that is what is causing the issue without stripping down the motor, but that will cost more than the motor is worth.

The engine is 4 years old and out of warranty, but has only been run about 20 hours. Most of it's life it has been stored in the shed apart from a few months when I kept it on the outboard bracket on the boat. I flush it and run out the fuel in the carby before putting it in the shed.

So, has anyone heard of holes forming in the cylinder walls of an outboard before?

Quite right NowandZen - it is a cheap Chinese motor. But I would have thought the inside of the cylinder, that was coated with oil would have been the last place to corrode. Would have expected the cooling jacket to go first.

A friend had a Chinese engine, a Maxus. The quality of the parts is absolute junk.
The impellers would last two weeks before shedding their fins. It would keep
stopping and refusing to start, the agent took an interest as to why this was all
happening and discovered a manufacturing flaw in the carby float, it split along
a seam. The replacement float did the same as did the next float. The engine
was supposedly modelled on a Yamaha. The agent conceded that the engine
was a reject and arranged for a complete refund.

If you're even remotely mechanical, you'll be able to sort it out. Providing you're patient and careful.

Make sure you have spark. Make sure there is fuel getting into the combustion chamber. The Starter fluid is often a good way to see whether it's fuel related. Re- do the compression test yourself, but saying it has compression won't necessarily give you a start, even if you have spark and fuel. You need to know the compression specifications first. It may well have 110 psi, but really needs a minimum of 160 psi. Two strokes need to have good vacuum as well, so they bring the fuel into the chamber. Do a bit of a google, there will be someone out there who's had the same issues and found a fix.
Being water cooled, they're not quite as easy as a lawnmower, but the principle is the same. The holes may well be ports, if they're of even shape and in the right place, but they may also be corrosion holes.

The cheaper engines don't have any coating on the inside of the water jackets, just bare alloy. Flushing may not help much as there will still be condensation left when you put the engine away.

Start with the basics and keep going until you find the problem, but don't start dismantling until you're really sure you need to.

I've actually been quite impressed with their service department - once I found them. It looks like they may have a new web page with a contact form on it - hadn't seen it before.

Anyway, have been emailing them in China and they have been responding straight away. They have provided detailed information about cleaning the carby (which I'd worked out from Google, but this would have saved me that effort). They also pointed me towards the intake plate. My symptoms sound like this might be damaged. They also let me know that the motor is based on the Tohatsu M5B, and that some parts are compatible, whereas others can be ordered from them. I've been able to get a service manual for the Tohatsu, so I'm prepared to strip down the engine and have a go at fixing it myself.