What's wrong with my Mariner 4 2 stroke OB

[VicS]

It was after. We will see if I have continuing significant problems.

I have had a problem with the fuel hose coming unclipped and when I investigated this morning it was off, new connector needed as it seems to happen a little too regularly. The engine is greatly improved but may be in need of a tweek to mixture working under load rather than in a tank.

I did ask about replacing all the crankcase seals but was dissuaded by the mechanic who came highly recommended.

Remote tank? If so a bad connection, leading to air in-leakage, between tank and fuel pump could explain your symptoms. Worn O rings in fuel connector not unknown. Cheap after market connectors can be troublesome too I believe.

 

[ProDave]

Well I'm just back from the boat, and I've fixed it.

It wasn't water in the fuel. I found the carb bowl drain screw and that just drained clean petrol and made no difference.

I checked the filter bowl on the fuel tap, and the in line filter. No blockages there and fuel free flowing.

So I then took the carb off and took it ashore for a closer look.

I had the bowl off first. That all looked squeeky clean inside.

I then removed the slow running jet and poked through with a very fine piece of copper wire. Nothing visible came out, but upon putting it all back, it's now running and idling fine.

This is why I hate carburettors. It's fixed, without clearly identifying the fault. My guess is a minutely small spec of dirt or gunged up petrol came through when I poked the wire through, but I didn't see it, and will never know.

Still I've learned my way around it a bit more.

 

[FishyInverness]

Good to hear Dave, bet you're feeling pretty upbeat now after that?

 

[VicS]

Well I'm just back from the boat, and I've fixed it.

Thanks for the feed back.

 

[davidpbo]

and you spent nothing more than time.

 

[VicS]

and you spent nothing more than time.

But to a self employed person time is money. In the half hour he spent sorting out the outboard he could have done a whole day's work.

 

[ProDave]

But to a self employed person time is money. In the half hour he spent sorting out the outboard he could have done a whole day's work.

I like to think I'm a quick worker, but even I can't do a whole days work in half an hour.

Anyway, yes it was satisfying to "fix" it, even if I never positively identified the issue. but to further confirm it was the idle jet, I did some more tests before I took anything apart, and one apparent thing was the setting of the idle jet had no effect whatsoever while it was still faulty, but it did afterwards.

Quite apart from anything else, fixing it myself removed the need to find someone else to fix it, and the time and hassle of transporting it to whoever for them to do it. the cost of such a repair was a secondary consideration.

And I fully agree it's most useful to know your way around your own boat engine, so if it does give up at sea, you stand a better chance of sorting it out yourself.

 

[davidpbo]

But to a self employed person time is money. In the half hour he spent sorting out the outboard he could have done a whole day's work.

Depends on the cost of the repair and the rate the self employed person gets.

I've just had trouble with my normally reliable 3.5 Tohatsu.

Difficult to start then revs/power*dipping rythmically. I thought it was fuel starvation. Stripped the carb which was fairly clean but don't think the jet was screwed home fully. Still the showing the above fault, changed the spark plug for new, now running fine.

 

[Lakesailor]

The leak allows air to bleed into the crankcase and thence into the cylinder; since it tends to be erratic, the revs will rise and fall of their own accord. As Seajet says, it often also causes poor starting.

I am mortified

 

[Gwylan]

It seems to be deteriorating.

Starts fine.

Runs under load fine.

When running under light load (i.e low revs) it runs fine most of the time, but occasionally the revs will drop and it will sound rough, then go back to normal. Reading other threads I think this may be "4 stroking"

today returning into the harbour, it now does not like running at very low revs. To spite me it died completely as I was approaching the harbour wall (thankfully not a big problem today)

so I did some investigating when safely tied up.

It will start and run at idle, but sounds rough, like it's misfiring (is this the 4 stroking thing, only firing half as often as it should)?

Give it moderate power, and it will run for a bit then slowly die and stall (that's what happened pottering in at very low revs)

It's not a fuel starvation issue as it's fine at high revs / power.

I changed the plug for a new one, no difference.

I guess it's a carburettor issue. Don't just say "clean the jets" as I wouldn't know which one and how. I need a but more help than that.

I should add cooling seems fine, it's peeing nicely, and the water from the pee hole is barely tepid, so it's not overheating.

Sounds very familiar.
Drop the bowl off the carburettor and be surprised at all the rubbish in there.

Do not necessarily need to bother with jets if there is dirt in the bowl.
For most engines you can get a service pack of necessary washers, gaskets, a float and do a half decent job with a screwdriver and a pair of pliers.

Ask me how I learned this? Worst was it had been for a 'service' by a professional. Just a pirate without a funny hat and parrot.