in 08 only the 340hp engines have the cats. You will know if you have Cats because they have a huge sticker on the side caying tis a cat.

When it comes to fluids Marine just means extra cost in most things i have found.

Now i did notice my Indmar takes an off style oil. It says something like 15w40 or something like that. As i bought some 10w30 simi sythetic to put in it this year when i winterized and then before i poured it in i noticed it was the wrong oil acording to the sticker on my engine. So i had to buy more. So i guess the 10w30 goes in Claudia's car when it gets its next oil change around 19K since the first oil change wasnt due till 9.5k