Mariner 5hp 4 stroke problems

LONG_KEELER

LONG_KEELER

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I have a new to me Mariner 5hp 4 stroke.

The problems are as follows :-

Starts ok.

Tick over ok but slightly varied at times.

Under load, engine falters badly or stops with a 'phut' when put in gear despite using high revs. .

Restarts ok but the engine is not capable of providing power above more or less tick over revs without cutting out. Revs quite high in neutral but biggish delay.

Spark good. Plug nice brown base and not oily.

Choke operates ok on carb. Used fresh fuel in tank.

Any thoughts of where to start ?

Many Thanks
 
I had similar problems with my Mercury 4hp four stroke. Cleaned the carb although it seemed spotless anyway, no obvious blockage, changed the spark plug even though it looked OK, nice light brown color. Tried the engine in dustbin full of water and it worked perfectly.
 
I believe my Tohatsu 6hp (2006 model) is very similar to a Mariner 5hp. The holes in the needle jet are very fine and easily blocked. I understand each hole controls a different throttle setting so the engine may run fine on min tickover but cut out when opened.
I had problems with blockages caused by (what looked like) grains of sand in the fuel tank. Three years ago, my carb & needle jet were professionally cleaned in a sonic bath. I've since dismantled it myself a couple of times and cleaned with a can of carb cleaner from Toolstation.
When dismantling, check for any water or debris in the carb bowl. Also check your fuel tank - rinse with clean fuel if in doubt. Does the fuel line filter look clean?
Hope this helps...
 
Most probably the main jet.
Best fix is to dismantle and blow through with air line. Often you think it's clean but a little bit of gunge gets into the jet.
Second area to look is the fuel filter on the line from the tap to the carb. £25 as a genuine part so search for a (small) motorbike one on ebay.
 
Adrian at AC Outboards specialiizes in Mariner - highly recommended if you're going anywhere near Peterborough/Stamford:
AC Outboards, 3 Stirling Way, Northfields Industrial Estate, Market Deeping, PE6 8LG
tel 01780 480.169 Mob 07850 489.122
Excellent engineer but can be elusive - appoinment essential!
 
LONG_KEELER said:
I have a new to me Mariner 5hp 4 stroke.

The problems are as follows :-

Starts ok.

Tick over ok but slightly varied at times.

Under load, engine falters badly or stops with a 'phut' when put in gear despite using high revs. .

Restarts ok but the engine is not capable of providing power above more or less tick over revs without cutting out. Revs quite high in neutral but biggish delay.

Spark good. Plug nice brown base and not oily.

Choke operates ok on carb. Used fresh fuel in tank.

Any thoughts of where to start ?

Many Thanks
Click to expand...

Hi
I had exactly the same problem with same engine a couple of years ago - stripped and cleaned carb 2/3 times and blew all through with an air line
no difference so then I cleaned and reset plug gap - although it looked good anyway - again no difference - then at last changed the spark plug - result at last - so now i carry a spare plug and that would be my first move
 
I had similar - we prob all have done at some point. Did all the carb stuff, new fuel etc. But I think it was down to a bad plug (very corroded) and when holding the HT lead I could feel a shock going up my arm when trying to start. So new plug and trimmed an inch of the end of the HT lead and all good.
 
Dabhand said:
I had similar problems with my Mercury 4hp four stroke. Cleaned the carb although it seemed spotless anyway, no obvious blockage, changed the spark plug even though it looked OK, nice light brown color. Tried the engine in dustbin full of water and it worked perfectly.
Click to expand...

+1 .. I'm a convert to this... change the plug anyway - three or four quid and often surprising results
 
Well................................

I feel a bit of a herbert.

Changed the spark plug first and the engine is running as sweet as a nut.

I'm smiling .:)

Many thanks to all.
 
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