what plugs

[ukprometheus]

what plugs would evryone suggest for a 91 mariner 2stroke 50hp.
reason i ask is my cousin has one and its fine when cold but once warmed up it tends to stall at idle and it was suggested he use a slightly hotter plug.
fuel mix is 75:1

[uncle al]

I suggest that only factory recommended plugs are fitted for optimum performance, your problem may be else where (ie)carb setup ,wrong mixture, dirt/water in fuel or any one of a dozen reasons, you start messing around with sparkplugs with differant heat ranges and you could be causing p/h damage, running to hot/cold

[ukprometheus]

fair point

[Turbodiesel]

Originally Posted by ukprometheus

what plugs would evryone suggest for a 91 mariner 2stroke 50hp.
reason i ask is my cousin has one and its fine when cold but once warmed up it tends to stall at idle and it was suggested he use a slightly hotter plug.
fuel mix is 75:1

What serial number have you got and i will tell you what you should be fitting!

[captnjack]

I've never heard of a 75:1 ratio. Its always been 40:1 (for lawn equipment mostly). 50:1 for older outboards or 100:1 for most of the latest 2-stroke OBs.

Is 75:1 something unique to just a few model years or maybe just Uk verisons?

[ukprometheus]

the original plan was to run the engine at 100:1 but thought to help wear on the engine run it at 75:1
maybe that was not such a good idea

[Tris]

I have heard of running a hotter plug. I worked on a 2stroke 115 IIRC and it would not produce full revs, spoke to an "outboard guru" and said, it should have these try these. and the thing ran like a dream full revs and about 10knots more

[m chappelow]

If the engine is running on high revs most of the time I wouldn't bother with a hotter plug but for an old 2stroke engine that's used at trolling speeds or like on say a canal for very long periods they can be beneficial and help stop oiling/fouling up of plugs.

[ukprometheus]

anyone suggest a hotter plug for this engine then

[willk]

Originally Posted by ukprometheus

the original plan was to run the engine at 100:1 but thought to help wear on the engine run it at 75:1
maybe that was not such a good idea

So let's look at this again: He's "over-oiling" the fuel mix and he's stalling at low revs.

I'd clean the plugs (or maybe fit new ones if they're old) and try the correct mix, see how it goes. If that fails, plan B beckons!

[J.W.W.]

If you could give the serial number I'm able to tell you the ones which mercury prescribes in MIDAS.
Rgrds Wouter