DF70 idles but won't run at speed

I have a Suzuki DF70 I purchased new in 2008. I have always used "Marine Sta-Bil" with E-10 fuel. In October, 2012 I switched to "Startron". On first outing after the switch the motor cranked and ran fine, but after running down the river at full throttle for about 5 minutes the motor started acting up and slowing down. I throttled it back up and eventually it cleared up and ran fine. This happened once more that day. A month later I launched the boat to fish and it ran fine all day. On December 28, 2012 we launched the boat and it cranked and ran fine. We ran down the lake a mile or so to our first honey hole and fished about 2 hours. Cranked the motor to move and it ran fine. After idling out of the cove, which took about 3 minutes, the motor shut off. After it cut off it would start and idle, but when I shifted into gear it cut off. I placed the shifter into warm up mode and cranked it and it idled but when I gave it some gas it shut off.*

What could be the problem, and how can it be corrected?

Thanks,
Skiffman

A friend advised me to sign up for this forum because it is so helpful. He has never lied to me before. I guess I made the mistake by registering and asking for help, because apparently newcomers are shunned.

Sorry, but your motor is not in the " easy to service at home " category.----It is a fuel injected / multi sensor / computer controlled machine.-------Plus the Suzuki dealer net work is not considered to be the best set-up in many parts of the land.-Not many folks are here that can give advice on such a machine from far away.--Have the fuel filters been serviced ? --Do you have a factory service manual ??---------I have a manual for the 50 HP Evinrude / Suzuki machine and reading that is challenging to say the least.--I have a number of those ( 50 / 40 HP ) because dealers said " not worth the bother to fix them "-------------I know that is not helpful to you but that is the way I see it.