Your dipstick hooks into the bottom of the oil pan, and the tube is also used for pulling the oil out of the engine when you change oil. So using some automotive type dipstick will mean you can't get the oil out of your engine easily.
Your tube and dipstick is a Mercruiser part only, do you have the serial number for your engine. If you do, most any site with the OEM parts lookup will allow you to fine the correct parts.
