Mariner 3.3 running weak

Dazedkipper

Dazedkipper

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This has started recently, previously it ran well. The engine starts ok, 2nd or 3rd pull from cold and first time when hot but until it's run for about 5 mins it needs choke, usually 1/2 to 2/3 to keep it running properly. I've cleaned the tank, am using new fuel too. The carb has been dismantled and cleaned. Someone suggests new spark plug although can't see how that can effect the mixture. Any ideas welcome....
 
Worth checking plug gap and/or trying new plug as not expensive.

Assuming that it's not just the colder weather now here (!) or someone has accidentally adjusted one of the carb settings, then a partially blocked/gummed/corroded jet is probably the most likely suspect.

Richard
 
Have you cleaned the fuel filter ........ part of the fuel tap assembly and checked that you get a good flow of fuel to the carb.


Symptoms are those of a partially blocked jet.............. poke through with a soft copper wire


Rebadgd Tohatsu I beleive. Carb more or less identical to this one ( courtesy of L.S.) Tohatsu carb

Definitely fit a new plug ........ frequently cures problems when all fingers point to carb problems.
 
Thanks all, wasn't aware of the filter so will try that. Also a new plug. Thought the carb was cleaned ok but if the above doesn't sort it I'll look there again.
 
Its usually old stale petrol glop. the residue can live just above the fuel tap and is hard to get rid of.It also lives in the carb and needs a complete stripdown somewhere safe like in a bucket, to avoid losing parts.Discard all old fuel on reassembly.As OP says jets need care if blowing with compressed air perhaps a better idea.
The other problem commonly encountered is the impellor losing its vanes.The tell tale water squirting down from the head should always be present.Impeller is up the leg instead of behind the prop, if your motor has neutral lever.
 
I would also change the spark plug, I carry one Well wrapped in cling film in the casing and its quick and easy to change. I usually do this early on in the proceedings, its surprising how often these wee beasties wreck spark plugs.
 
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