[JL8Jeff]

This is pretty basic but I must be missing something in my old age. The engine is a ZZ3 350 that was in a 1985 Corvette. I put the engine in my jet boat and just hooked up all the wiring but when I turn the key to start, I get nothing. I put the voltmeter between the start wire and the start terminal on the solenoid and when I turn the key I get 12.5 volts but no action. I tried a new solenoid and got the same thing. I took the starter with the old solenoid(I rotated the power lead post so it was sure to make good contact) to Autozone and they put it on the machine and everything checked out fine. The first time was sluggish but after that it sounded like normal. I put it back on the engine and get the same thing. I put a screwdriver across the power lead post(which has the battery cable connected to it) on the solenoid and the start post on the solenoid and it engaged and cranked over the engine. I hooked a jumper wire from the positive post on the battery to the start post on the solenoid and got nothing. I would think that the full battery power (12.5 volts) going to the start post should engage the solenoid and starter. So what am I missing here?

Edit: I don't have the engine grounded to the aluminum hull, I'm wondering if I need to.
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