2 stroke problems

[mike_1987]

Hi all I’ve got an old but until last night very reliable mercury 2.5 outboard
Last night it started well ran for a bit then the revs started fluctuating until it cut out it would then restart immediately but start with the spluttering and for about a minute
Managed to limp back to the pontoon and have a look at it

took the spark plug out and it was soaked so let the engine drain overnight with the plug out
This morning started it up ran it for about 10 minutes absolutely fine then it repeated last nights issue
Tools are limited till I get home during the week but does anyone have any ideas where to start looking

ps engine ran perfect 3 days previously and has never had issues before fuel is fresh and using good quality oil

 

[VicS]

If the plug was wet with petrol it suggests the carb is flooding due to the float needle valve not closing properly. It may be worn or sticking or not seating due to some dirt.
Make sure the choke is opening properly
Check the float as well
Check the spark. strength. It should be able to jump at least 9mm. Always worth trying a new, correctly gapped, spark plug. but if it starts easily spark or plug probably not the problem

 

[westernman]

Hi all I’ve got an old but until last night very reliable mercury 2.5 outboard
Last night it started well ran for a bit then the revs started fluctuating until it cut out it would then restart immediately but start with the spluttering and for about a minute
Managed to limp back to the pontoon and have a look at it

took the spark plug out and it was soaked so let the engine drain overnight with the plug out
This morning started it up ran it for about 10 minutes absolutely fine then it repeated last nights issue
Tools are limited till I get home during the week but does anyone have any ideas where to start looking

ps engine ran perfect 3 days previously and has never had issues before fuel is fresh and using good quality oil

Sounds like a gummed up carb to me. 3 days previously, was it running on old fuel or new fresh stuff?

 

[mike_1987]

Sounds like a gummed up carb to me. 3 days previously, was it running on old fuel or new fresh stuff?

Newish (3 weeks old or so)

 

[ashtead]

I have a merc 3.3 2 stroke -your symptoms sound familiar - you might look online for a new carb ? If you find one let me know a source as I have in mind to take this route.

 

[mike_1987]

Sounds like a gummed up carb to me. 3 days previously, was it running on old fuel or new fresh stuff?

Would brake cleaner sort it temporarily or is it a strip and rebuild thing

 

[VicS]

Would brake cleaner sort it temporarily or is it a strip and rebuild thing

If the carb requires cleaning it's a strip and clean job. Cleaning the jets with a soft copper wire. Just spraying with any sort of cleaner will not clean blocked or restricted jets.

 

[Aussie farmer]

Sounds like gummed up float needle, if you can get the bowl off carby, slip the pin out that float handles on , do not drop the needle or pin.
Check for gunk and look at pointy end of needle to check it gets a seal.
Might aswell turn feul on whilst pulled apart and check you have a gentle steady flow. Should be a small filter in base of tank where hose connects if no flow but sounds like you are getting to much.
Reassemble and test.
Pull spark plug out and check the spark is strong. There's a good chance your plug works when cold but breaks down when motor warms up , test when warm if possible or grab a new plug and whack in it.
Anything more than that may need to wait till you are home.

 

[Spirit (of Glenans)]

I have been known to forget to open the tank breather.......

 

[wazza]

Hi all I’ve got an old but until last night very reliable mercury 2.5 outboard
Last night it started well ran for a bit then the revs started fluctuating until it cut out it would then restart immediately but start with the spluttering and for about a minute
Managed to limp back to the pontoon and have a look at it

took the spark plug out and it was soaked so let the engine drain overnight with the plug out
This morning started it up ran it for about 10 minutes absolutely fine then it repeated last nights issue
Tools are limited till I get home during the week but does anyone have any ideas where to start looking

ps engine ran perfect 3 days previously and has never had issues before fuel is fresh and using good quality oil

Yep I’m with other comments here and say it’s the carburettor. I’m have a 3.5hp Mercury & pretty much every season I have to do a clean of it otherwise it has the same problems you’re having..

 

[neil_s]

Given that your 'morning after' effort was successful while the motor was cold, I'd try a new spark plug before any dismantling.

 

[mike_1987]

Well I’ve managed to get the carb off needed to dremmel a slot into some of the screws where they had rounded
I’ve come to realise I have no idea whatsoever how it works I’ve ordered a new one along with a spark plug air filter and fuel tank filter
In the meantime I’m going to strip the old one and see if I can get it working as a spare as I dislike not knowing how to fix it

 

[mike_1987]

I have a merc 3.3 2 stroke -your symptoms sound familiar - you might look online for a new carb ? If you find one let me know a source as I have in mind to take this route.

Found an oem one on eBay about £90
Got a lookalike for 25 from eBay

 

[jamie N]

They're terribly simple carbs, and you'll easily restore the original, and have a very reasonable replacement spare as well. £25's OK!

 

[mike_1987]

They're terribly simple carbs, and you'll easily restore the original, and have a very reasonable replacement spare as well. £25's OK!

To be honest looking on YouTube it’s not rocket science I’m very aware it’s very thin metal and I e had to fight the screws holding it in off so I’m likely going to break something in the process of trying to fix it

 

[ashtead]

I suspect the £25 version will be worth a try . I’m also not certain even with a few hours labour success would be achieved but if I can get it running again with new carb might save a whole load of hassle.

 

[mike_1987]

An update perhaps I’ve buggered it
Got impatient waiting for the new plug and carb to arrive stripped cleaned and reassembled the carb wire brushed the plug
Now it won’t even start let alone run rough and cut out
Getting what I think is a good spark will check against the new one tomorrow when it arrives
As it stands I’m thinking of splashing some cash in a brand new 4stroke I have about a mile or river to motor to get to my boat and it’s not an enjoyable paddle in a dinghy that’s more inclined to row in circles

 

[Dipper]

I have a Suzuki 2.2 two stroke and that started playing up. Ran for a few minutes then cut out. Started after about a minute, ran for 30 secs then cut out then same again and again until I reached my destination. A new plug sorted it for a couple of trips then then the same happened again this time in Dartmouth. I took it to a marine engineer and after checking everything he put in yet another new plug and it's run fine ever since. As mentioned above, it's always worth trying a new plug first and maybe even two new plugs as was necessary with my engine. I now carry a spare.

 

[mike_1987]

New plug started 3rd pull and ran like a bag of something foul smelling
I believe it’s running rich due to all the smoke and wet plug when checked new car arrives sometime between now and next lifetime
I’ll update when it gets here
Thanks for all the pointers

 

[mike_1987]

Update again I am a fool
I hadn’t tightened up the main jet fully so It had vibrated into the bowl all tightens fully and now she runs sweet as a nut