How important is it to change outdrive fluid every year?

My boat is a couple of years old and I'm wondering how important changing the outdriver oil every year is. I've previously done it just because the manual says too but as a typical summer weekend boater I%26quot;m wondering how much abuse the gear lube actually takes. I have an Alpha drive and run High Performance Merc gear lube. I'm not due for an impeller change this year.How important is it to change outdrive fluid every year?I've been a marine Mechanic (Certified Mercruiser) since 1974 and but recently I've changed my position on this maintenance item. It's actually possible to check the oil for water, without draining and replacing. I've also pressure tested and vacuum tested lower units to check for seal leak. So, given the very limited amount of use, and the quality of the oil, I check but don't replace unless needed.



Edit. The above position was not taken lightly, but after years of experience and training........Changes in the lower unit oils, and an awareness of being more %26quot;Green%26quot; convinced me that %26quot;always%26quot; draining and replacing was not necessary in 2009.How important is it to change outdrive fluid every year?it's not so much the lube issue.. it's a water issue.



If water gets in and sits over winter... well you see where this is going...How important is it to change outdrive fluid every year?Servicing the lower end is the only time you will see if there is a seal leak developing or already happened. It is also a time to see if there is any excess metal fragments in the oil. Seals in particular give you no sign of failure externally until way too late - it is possible to unwrap the boat after winter and find the bottom end a seized, rusty mess requiring full rebuild or even total replacement. Not good.How important is it to change outdrive fluid every year?Let me make this very simple.



Lower unit/outdrive lube change $30 of lube and $1 to $2 for felt washers ($11 for the hand pump if you don't already have one) versus +$2,000 in replacement/repair costs.



I'll take the $30 a year over one outdrive replacement/repair anyday.



Not to mention you must check for seal leaks and the gear lube condition anyways annually.