Changing out Serpentine Belt and pulleys

Willhound

Prepping for an upcoming trip, and reading some of @Stodge 's trip log, I'm going to change out my serpentine belt and while I'm at it, I might as well do the idler and tensioner pulleys. I'll keep the old one's as spares.
The belt generally looks ok, no cracking, but showing signs of wear, but I know it's been around a while with a number stamped on it of 57-862087 which has been superceded quite a while back it seems by 57-865615Q03
I do see a Sierra cross reference for a 18-15100. I also found a cross reference here: http://crossbelts.com/serpentine/6ribkseries.html  that show's equivalent automotive belts from makes like Dayco, Gates, Goodyear etc. 
These might be easier to source where I am. I've read everything from "go ahead, it's fine and save half the $$$" to "Don't you dare, your boat will immediately explode, take out every other boat in the marina and you'll burn in non-marine part ****!!!.
Thoughts?
The Tensioner according to Mercruiser EZ-Parts lookup is 807757T or Sierra 18-6457. Also found a Dayco 89014. Not sure if there's any others or not.

The Idler is 27-818382. I can't seem to find a cross for this one, but it seems easier to find. I might just order it off Flea-bay.

Black_Diamond

If you don't get the Merc belt, stay with Gates or Goodyear.  

Willhound

Black_Diamond said:

If you don't get the Merc belt, stay with Gates or Goodyear.  

Kinda what I was thinking. I've used Gates for years in other applications even going way back to my snowmobile racing days.

Liberty44140

I replaced mine with gates this year. Bought them from Walmart.com. Would not do that again because while they are the same belt, they came from 2 different lots (printed lot numbers on the belts) so they were just slightly different lengths. They were within spec and they work fine but next time I will buy them at a physical store so that I can confirm same lot numbers and everything. No regrets about going Gates and saving a lot of $$$

Willhound

After checking a few local marine retailers (none had the parts, and most seemed confused by some of the part numbers) I ended up ordering all OEM parts on Flea-Bay from the US. Even with exchange and shipping I saved enough on the belt alone to cover it. Belt and both pulleys, all from an outfit called "Busters Marine Service". Should arrive in plenty of time to get them changed out before my planned trip in a couple of weeks.

Liberty44140

I've ordered from Busters, was a good experience 

Cableguy Greg

Busters is great until you have to return something. I ordered a new all around light that was taller than my current one and Attwood has changed the base with different screw holes. I didn't want to drill out my arch, so I returned it and they charged a 20% restocking fee. I get the fee, but it never mentioned that the base was totally different from the original one. Lesson learned on my part.

Willhound

I was a little nervous ordering online too, especially from the US. Returns would be a nightmare. I quadruple checked the part numbers on the Mercruiser parts site so as long as they send the stuff I ordered, I should be ok.