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Greetings! I am new to marine craft, and have several questions about my 2005 FX Cruiser HO that I purchased and ran all last summer with no issues whatsoever. The ski has approx 125 hours on it and is due for some maintenance. I've ordered the factory Yamaha service manual and am anxious to get started, so I thought I'd get some advice here too. First off, what oil is best for marine engines? I've used Mobile 1 in everything I've owned for years and want to know if marine oils have additives that are specific to the boating world (moisture resistance?) Nothing against Yamalube, but I do like Mobile 1 products. Second, I'd love to get a bit more hp out the ski, are there aftermarket air filters like K&N that help the motor breathe better than the OEM filter? Lastly, and most unfortunately, the ski would not turn over after sitting since last Oct. I did do a winterize last fall with flushing the cooling system, cleaning and lubing everything, and adding fuel stabilizer. I DID NOT, however, disconect the battery from the cables like it says in the owners manual. DUH. I put a meter on the battery today and it read 8.1 Volts. I'm under the assumption this is a 12VDC system, so the battery either needs charging or replacement. I'd like to to charge the battery, and see what happens. Should I charge it on standard or deep cycle mode? Thanks in advance for the advice on these three items.

Steve F
Atlanta GA
 

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1. Marine oils have additives that help with moisture, etc. that occur in a marine environment. The best ones have a FC-W rating by NMMA: http://webcache.googleusercontent.com/search?q=cache:1xDIKeKKaeQJ:www.nmma.org/assets/cabinets/Cabinet456/FC-W-2010-Mar11-2011.xls+2010+registered+fc-w+oil+list&cd=1&hl=en&ct=clnk&gl=us&client=firefox-a&source=www.google.com. I know one guy that runs Mobile 1, but he changes the oil at really frequent intervals (like 20 hours). I know for a fact that a friend of mine contacted Mobile, and ask specifically about running their oil in his ski, and the tech told him, and I quote "absolutely not". In his case the ski was still under warranty, and the tech told him he could possibly void his warranty. He ended up going with Royal Purple synthetic after he talked with their tech. Evidently the RP has the necessary additives, and is close to being certified by NMMA, but it is expensive at over $10 per quart. Fortunately, you have other good choices as seen from the list like Quicksilver, Mystik, and Amsoil. I'm running Amsoil 10W-40 Marine 4 stroke in mine. Interestingly Yamaha recommends their 10W-40 4W (W=watercraft, M=outboard motor) for their skis, but this oil has not been certified FC-W by NMMA as of yet, although their 10W-30 outboard oil has. I know some guys that run 4M (outboard) oil in their skis, but others that say you should run only 4W (watercraft).
2. I like the K&N oil filters, just because they are easier to get off (they have a lug on the back). There are after market air filters made by both R&D and Riva, both are a few $ less than the OEM air filter (still expensive $85+), but will provide no measurable performance improvement over the OEM filter. No reason to change the air filter unless it has oil on it, or is excessively dirty.
3. If that was the original battery then it is dead (8 volts = bad)........they do not survive a full discharge. The only batteries that do are the deep cycle type. Even if you can get it to accept a charge, it will be unreliable, and die on you when least expected. Get a new one. I recommend AGM type. Many guys really like the Odyssey: PC625 Odyssey Battery Expensive, but very long lasting, and vibration resistant. If your battery is a sealed deep cycle type, you might be able to revive it. Get yourself a Battery Tender Junior to put your battery on next year.
4. For a guide on changing oil, plugs, and other maintenance check out this site and scroll down: Technical Tips for your Yamaha PWC / Jet ski - Full Wave Marine
 
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