Alot of people on the forum told me to check the compression, so this friday im fixin to buy a compression meeter and check it. I'm hoping nothing serious is wrong with it cause this is our first boat.The motor is 1975 70hp Evinrude.My neihbor is longtime mechanic with vehicles and he thinks it something with the carburators, so if the pistons are fine which they probably arent, what could be causing this problem.When its hooked up on the water flusher its works fine.

was the boat sitting any amount of time

My Yamaha was doing the opposite;dying when shifting into reverse,as in pulling up to the dock.The first time was pretty embarassing,banged into the dock.A friend w/some outboard knowledge said the raise the idle some and that fixed it.Good luck.

I had a similar problem with a '79 Evinride 100 - had bad power pack on one side. Have a mechanic do a spark check.

There is no ignition interruptor switch on that motor like some that J/E made as well as Mercrusier. So that leads you to one of 3 things, carbs dirty, idle too low, ignition not firing on all cylinders.