3.3hp 2-stroke troubles

[nicksharpe]

Evening all,

Some advice, if you please:

I have a 3.3hp Mariner as an aux engine. Bought second hand from a dealer about a year ago. As there's no room on my transom (4.5m Avon), I keep the thing lashed down horizontally in the back of the boat, above any water that might be washing about back there while running.

I've barely used it, and came to try it a few weeks ago and it wouldn't start. After much pulling it eventually got going, but was stuttering and would die if I opened the throttle. At the same time, the telltale was very weak to non-existent.

I decided to try my hand at fixing it, so bought a book and watched a few YouTube vids which prompted me to order a new spark plug and successfully change the impeller (telltale issue now fixed).

I installed the new spark plug, but the engine wouldn't start at all. Imagine my confusion. Reinstalled the old spark plug and had same problem as I'd started with - the engine starts, but struggles when I apply throttle (in a tank in the garage). Once I've stopped it, I can't start it again for ages.

I'm at the very limits of my knowledge and wondered if anyone could throw some ideas at me to check. It's either that or take it to the outboard shop and fork out pretty much what I paid for it (£250) to get it fixed...

One tiny thing to add: I also bought a feeler gauge and have checked the gap on the spark plug is 1mm, which I believe is correct for this engine and is the same as the plug which was in when I bought it.

Thanks in advance,

Nick

[jeffstevens763@g]

Before storing did you run it dry and how old is the fuel

[nicksharpe]

Originally Posted by jeffstevens763@g

Before storing did you run it dry and how old is the fuel

Stored with fuel in, and the fuel is eighteen months old. I'm starting to think that might be the problem... I hadn't realised it was that old.

[jeffstevens763@g]

been there Nick with an AUX although ive had fuel in garden equipment and its been ok at 2 years. sods law i treat mine now and no issues for the last 5-6 years.

[GordyP]

Was trying to run my 2.5 tender engine on old fuel recently, ran like a bag of spanner’s. Fresh fuel and it’s running perfectly! To be fair the old fuel was probably about 4 years old.

[jeffstevens763@g]

Originally Posted by GordyP

Was trying to run my 2.5 tender engine on old fuel recently, ran like a bag of spanner’s. Fresh fuel and it’s running perfectly! To be fair the old fuel was probably about 4 years old.

i wonder if you had put fuel conditioner in, it would have brought it back to life?

[GordyP]

I still have half a container of it! Think it’s probably best for starting bonfires!

[spartacus]

The secret of auxilliary engines is to use them. Even if it's lashed down (not convinced having it horizontal is the best position). I've seen boats with them stored vertically behind a jockey seat or in front of the console.

Back to the engine. I'm sure the fuel is fine, but to rule that out, drain, refill with fresh and mix with 2-stroke oil. At this time of year, the ambient temperature should help. Ensure the fuel tank is vented, pull out the choke, and fuel cut-off switch isn't switched off.

To test the spark, unscrew the spark plug, and HT lead and ground it on the engine block. Turn it over - you should see a spark. Ensure it's dry, and try again with throttle open.

The little straw that comes with a can of WD40 is handy to clear the tell-tale on these little engines if you're worried it's not pumping properly.