Is it a marine 302 or not ??

What's wrong with marine engines? As long as it isn't counter-rotating. Just understand that most marine engines are usually the lowest of the low performance by car standards, the equivalent of the mid-70's smog stuff. Marine engines have low compression ratios and short duration cams which keep maximum power down and duty cycle up. We cruise marine engines at 3200 rpm or so and 2/3's of their maximum power output so it's best to keep the maximum power output low to keep wear low. Also, most marines sell only 87 octane. A marine 302 is likely rated for 190 hp which translates to 145ish horsepower by car standards. It's a good foundation, though. Marine engines usually get the heavy duty parts. For us GM guys, that means the x-rods and 4-bolt blocks as well as the cylinder heads cast with a little more material for better durability. The only real differences between a marinized engine and a car engine are the stainless steel head gaskets and stainless water pump internals. If it's a raw water cooled block used in the ocean, it may be rusted out inside of the coolant passages and be too thin to rebuild. This is usually not the case if it's the first rebuild. Oh yes, some engines (usually big blocks) came with exhaust valve rotators. These add a lot of weight to the valvetrain and can cause valve float at high rpms. It's best to remove those if you plan to do anything performance wise.