Re: MOTOR DIES AFTER 15 secs
Everyone has their own theories on troubleshooting usually based upon what has worked for them, or from professional training. Here's my version from hardknocks U.
On muffs you can have a dead cylinder and not even know it. Before you go to the lake again, get a can of Deep Creep (Sea Foam in a spray can).
To test ignition, slide a short piece of wire under the spark plug boot on each cylinder leaving the boots on the plugs so that they will fire normally, until the wire contacts the metal cap. The end needs to be accessible so you can touch it. Get the muffs on and water running and crank the engine, setting rpm's to 1000 or so.
With an insulated (handle) screwdriver touch the block (a bare spot) and move the shank of the driver over to the wire until you get a nice snappy blue arc. Should have roughly a 1/4" gap between the two when the spark jumps. All plugs should give you the same arc in size and color. If you find a lazy one, replace all your plugs and try again. If you still find a lazy one swap pulse packs with a strong one and see if the lazy one follows the pulse pack. If so, replace the pack.
Once that is finished and you are satisfied that your spark is ok, pull the cover off the engine and pull out the plastic plugs in the airbox exposing the throats of the carbs.
Get on the water with your spray can of Deep Creep and give it the gas while someone sprays some in the carbs. If you get an immediate reaction (power increase), you are suffering from fuel starvation caused by bad fuel, dirty fuel filter, cruded up carbs, or restrictions in your fuel pickup line.
My 2c
Mark
