I wait for NAPA to have their annual half price filter sale and buy a case. A buddy of mine gets his from his John Deere dealer at an even better price. A 4.3L Chevy is a 4.3L Chevy. Get good filters and change the oil before parking the boat for the winter and you are golden.
Since my boat only gets 40 or 50 hours a year of service, I use a regular 10-30 non-synthetic on the engine. Lately been Chevron brand from Costco. Since I change it every fall, it looks brand new when I drain it. No need for anything fancier.
I buy Sierra Synthetic marine gear lube for the drive (usually buy it from iBoats). It gets changed with the engine oil and the drive gets left on a stand for the winter. Easier on the bellows if the drive isn't cranked up all winter.
When I winterize my boat I run it on muffs until warm, hook up the vacuum oil suction to the engine then pull all the block and manifold drains and probe the holes with a wire to make sure they are open and fully draining. Then I pull the lower hose off the engine water pump to get the last of the water out. I add no antifreeze. I live in Idaho where it gets below zero. A dry block will not freeze or crack.
I then pull the outdrive. Change its oil on a stand. I do not replace the impeller except every few years seeing as how it, and most probably yours, are Alpha1 Gen2 model. The impeller, once you know if is good, will last for a number of years.
Make sure everything is put away perfect and your boat will not take damage in the winter. Changing all the oil before parking it will get any water contamination out before storage.
Enjoy. No reason to purchase OEM Mercruiser for maintenance stuff. Many replacement parts - you bet! OEM is the only way with a lot of them. Ask away here and you'll get the straight answer.
Rick
