sorry if this is a dumb question im a noob to boating but very mechanically inclined. i recently picked up a pair of 2008 350 mag mpi engines, i have read a lot about the cooling system but still a bit confused. the previous owner was running bravo 3 drives and i am going to run my alpha ones. what can i do about the cooling system as the new motors have the belt driven pumps i saw somthing about the hoses collapsing under the pressure if i use the alpha drive impeller and the belt driven system. any suggestions how i can get this set up correctly so i dont over heat? i really dont want to change to bravo drives at this time as im going on a budget build and already have the alpha drives.

you run or or the other. they will fight each other. if you run the drive pump, then you have to have the cooling system set up like a typical alpha. If you run the belt driven pump, you need to have a thru transom of thru hull water inlet. even if you use the belt driven pump, the pump in the outdrive still needs to be functioning to cool the drive. If the boat had B3 drives and your putting alpha/s on how big of a boat is this? You might be over stressing the drives.

the engines i got and am rebuilding was running the bravo 3 drives that was a 38 foot cabin cruiser, they are going in a cobalt 269 a 26.5ft speed boat i know bravo drives are the way to go but im trying to get her on the water on a budget with what i have my boat was originally set up for alpha drives. what do i need to set the motor up for alpha drives? do i need to run both with a thru hull pickup since the new motor needs more cooling or should i be ok with but the drive pump sysrtem?

Probably easiest/best to put pickups on the boat. The Alpha thermostat housings are different and if a Gen 1 drive won't deliver enough water.

Also - you need to come up with a shift interrupt or the Alpha's wont come out of gear.

Did the boat have previous motors and drives that can be harvested for needed parts? If so you may want to do an Alpha cooling system and shift interrupt.
Or as said you can install a cooling water pickup to use the existing Bravo style pump. That will probably cost less if you would have to get the cooling parts separately.
Don't worry about the Alpha cooling system running without feeding the engines. It needs to run to keep it's gears healthy. Also it should have a water source whenever the engines are run to lubricate the impellers. I believe the water can just be let go inside the drive. You can do some research on that but I think the pump in the drive can have the upward facing water tube removed so the water just flows into the central cavity and out between the drive and the boat's transom plate..Otherwise it will show up in the boat!
And, as said, the Alpha's do need a shift interrupt .