Re: Chevy 350 Engine/Mercruiser 5.7 Problems!!
I hope the gauge was wrong and you actually had oil in there.
What I think I'd recommend is when you get your boat back from the shop, every time you get it back, do some basic checking on it yourself before you try to go on the water.
That means check to see that it has the right amount of oil, make sure the plug wires are on tight, look it over for obvious problems. If you have a freshwater cooling system, check the coolant level in it. Check the level of power steering fluid if you have that. Check the battery for good voltage, and if necessary check the level of electrolyte in the battery.
All these are just basic maintenance checks, like you would do on a car, and they can save you a lot of hassle and money.
Once you have these done, then connect the boat engine to a set of muffs (earmuffs for cooling water, they attach to a hose and clamp on the engine when it's in the driveway) and start the engine on the trailer with the water running. Don't go above about 1000 rpm, and then only for a little while. Check to see that water comes out of the drive at the prop and near the transom. Also check the engine temps to be sure water is cooling it properly... the dash gauge will help with this, but an IR thermometer will help more.
Once you get it idling in the driveway for 15-20 minutes, then I'd have enough confidence to take it on the lake.
Given your situation I'd document the call to the mechanic. If there really was no oil in there, there's a chance the engine is seriously damaged by you trying to run it enough to get to shore. In that case you'll need proof of the advice he gave you in order to get them to fix the engine or pay for someone else to fix it.
Note for the future: If a gauge suggests a problem or the engine runs funny, the very first thing to check is the oil level. An engine without oil or not having enough will self destruct in short order, and it's much, much more expensive than getting a tow.
Good luck,
Erik