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1993 Mariner 40 Hard start Rough Idle Dies going into gear

S

skidmark

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"Hello all -

The (almos

"Hello all -

The (almost) new GF has a pontoon with a 1993 Mariner Magnum 40HP 4 cylinder/2 stroke on it.

The engine seems to me to be a little hard to start. It idles OK, but not particularly smoothly. The real problem is that when trying to shift it into gear it always stalls. She has been running premixed fuel along with whatever oil the injection system contributes, so that explains the fouled plugs. Cleaning the plugs really doesn't help the stalling, though.

Since this (the engine, not the girlfriend) is about 40 years newer than what I'm used to playing with, I need some advice and direction. What are the most likely culprits and fixes that I should be looking at?

She's really pretty (the girlfriend, not the engine) so I'd like to make happy with this one.
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"
 
"If the motor has sat for any

"If the motor has sat for any length of time it could have developed a clog in the low speed carb jets - quite common - manifests itself as running fine on muffs or in a tank, but put it in gear under load in the water and idles like crap or stalls.

Often, running with the choke, or giving it some throttle will keep it running and it may actually run well at higher rpms.

Second cause could just be excess carbon/cooties. For 5 bucks you can pick up a can of "Power Tune" - a Merc product in a spray can that you spray into the carb throats with her running - cleans all kinds of gunk out - just follow the directions on the can.

In any case, I like the powertune and think it's worth using once a year (usually at the start of the season).

And if it doesn't help with your particular problem you are only out 5 bucks and few minutes of your time, but have a "decarbed" motor that will really run fine once you address the clog in the carbs..."
 
"Thanks again, Graham -

I t

"Thanks again, Graham -

I think that I'll start with the Power Tune, then move on to the carbs.

Should I have gasket kits on hand when I do the carbs? Also, are there any pitfalls that I'll hit when I R&R the carbs? I'll be working off the back of the boat in shallow water, so I'll likely float a big mortar mixing tub under the engine to catch the dropped parts when working.

One more stupid question: are the fasteners, etc. metric or Imperial?"
 
"Yes, at absolute minimum repl

"Yes, at absolute minimum replace the gaskets.

You can take the carbs off as a whole unit (any linkages will stay connected at the "other end of things" letting you get to a better spot to work on them.

Last part stumped me though - I would guess Imperial, but can't say for sure. I'm a Canadian - all our socket and wrench sets have been both since I was a teenager and I just kinda "see what fits"
"
 
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