i need to put a thru-hull in a 16 donzi for a water pick up for the motor,can anyone tell me the best type to use?

mrmagic, Welcome aboard!
Well there are a lots of different water pickups available from any number of manufacturers. Some of them are going to be to big for that size of boat. If you post some more information like what you have for motor and outdrive, we can better help you out. If you have an Alpha drive, why not just use the one built in the outdrive.

Magic

I have a perko bronze intake strainer 1 1/4 inch. Sealed it with 5200 a couple of years ago. Lots of water and no leaks. The 1 1/4 line goes right into my bravo raw water pump.

You want one which will mount on the transom. You'll also want one with a adjustable cutting edge so you can dial in the water pressure. Look at the IMCO or Stainless Marine ones. Remember, this fitting is under water so you should install a shutoff valve. If you were to develop a leak, the boat would sink. Seal it with 5200.

28 eliminator
thanks for the info
boat is a 16 donzi 351 with volvo i/o drive, speedmaster lower unit,not much room on transom with trim tabs.