I have a 502 mag mpi it wont start but will turn over i have changed all electrical parts cap rotor wires plugs coil etc but still no start can anyone help

Are you getting spark out of the coil? Did you check the kill switch? Had this problem on a buddys boat and it took is a couple hrs to figure out it was a bad coil wire.

start with basics.....air,fuel,spark...

Do you hear your fuel pump? Check all your micro fuses on the motor.

Hate to say this but kill switch? (we've all done it lol) Do you have the cool fuel or high/low dual pumps?


Where you at in Toledo?

+1... add to that compression... and timing..it all has to occur when it is suppose to...

Assuming engine is solid (has compression and and correct cam timing) check for spark.

Check for spark at the coil wire and then at the plug...if yes go to checking for fuel...if no spark find out why.

If you have spark... check for fuel...fuel pressure and injector pulse...

Proper diagnosis is going to be way more cost effective than the change parts and guess method.

+1 on that, its very important to systematically diagnosis a problem rather then simply replacing things till you get lucky. You need to find the issue and its cause, these engines are tremendously reliable and many times its a simple fix or atleast a simple diagnosis. Start with fuel and fuel delivery, check to see that the pump is functioning and not just humming. From there make sure it is getting fed, filters and lines are clear (i dont believe you can blow back through the lines they are one way valved) . From there its on to electrical, relays, spark, dist cap and pickup (the distributors pickup can go bad). Had a no run issue on a 38 Baja last week that turned out to be dried out cracked old fuel lines, few days later no run issue again that turned out to be the high pressure pump in the vapor tank. It hummed and sounded like it was cycling but it was not after checking for pressure (boat has not been used in 5+ years so she's gonna have some gremlins)

Checking the computer for any codes may shed some light .....

South toledo heatherdowns area

Check the fuses under the plate that has the main breaker on it