Merc 15 problems

[Guest]

Hi ,
I have an annoying problem with my 5 year old Mercury outboard, starts fine but will not tick over unless I increase tick over speed, and occasionally cuts out at the most inconvient times.

The engine is used weekly but only to get me out of the Sailing Club, I have stripped the carb and as a precaution replaced diagphram and cleaned the filter plus tank. Fuel consumption is excessive and smoke issues from a vent at top of shaft in vicinity of powerhead, power seems normal and cooling circulation good.

Anyone got any suggestions?

Pete

 

[ChrisP]

Check the 2 stroke mix.

ChrisP

 

[oldharry]

There are a number of things could be wrong, and from your description the most likely seems to be a blocked or damaged exhaust. Assuming fuel mix, and carburation to be correct as you have already looked at these, then you probably have a problem with the engine itself.

You do not say whether you have checked the carburettor jets? Any muck or contamination will cause major problems. They are usually easy to remove and check, but make sure you put them back correctly or the engine will never run! Take the carb off, and check that all the drilling are clear - anything suspect, get your garage mechanic to blow it through with his airline. Proprietary 'Carb cleaner' sprays sometimes help remove accumulated gum and gunge from an engine that spends most of its life standing idle.

Check the exhaust system is not blocked. Excess back pressure will mess up tickover.

A rather more difficult fault could be low crank case pressure, caused by damaged crank seals. This is difficult to check, and even more difficult to put right as it involves a full strip down. Do not attempt this without being fairly sure this is whats wrong, as most outboards are pigs to strip, and most of us do not bother! This is the most common reason for junking 2 strokes. Symptoms are: poor starting, erratic tickover, stalling at tickover, and smoky exhaust. BUT: Any of these can be caused by other faults too, so dont jump to conclusions.

Is the iginition timing correct? If the flywheel key has sheared the timing could be haywire.

2 suggestions: 1 increase the tickover speed to the point where it does not stall. It is often possible to raise the tickover by a 100 rpm or so and prevent stalling, without too much gear crashing. If you can only engage now with a loud clunk, or if it is at all difficult to engage the gears, do not continue to do this or you will soon wreck the dog clutch.

Or: take it to a repair shop and ask them to quote for putting it to rights. You will then get some idea of what is actually wrong, and whether it is worth getting them to fix it, fixing it yourself, or if it has actually had it altogether..

 

[Guest]

(old harry) Thanks for your advise very usefull, will get a friend to assist me removing the engine this evening, I presume I will need to drop shaft to check exhaust. Just hope my tender engine will be strong enough in the meantime


(ChrisP) mixture spot on, also thanks

Pete

 

[oldharry]

Re: one other suggestion

Before you start pulling things to pieces, get the relevant @Clymer' manual - or equivalent from your local outboard stockist. It gives detailed drawings of how everything is assembled, and how to take things to pieces wqithout causing damage. Its quite often not at all obvious, even impossible to get things off if you do not do it in the right sequence.

Manuals are expensive - Clymers usually retail around £25 a go, but the info is well worth it if you are going in any depth into the engine!

Just hope it is something nice and simple!