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Oil spec for mine at least 30 weight or heavier, with no 0W-30 allowed (but 5W-30, etc. are OK). Volvo Penta's own oil in Europe is supposedly Mobil 15W-50, so I went with that given it's fairly cheap at the local Wal-Mart. I think they want SL spec or better too if you don't use oil from a Volvo bottle.

I clarified several things from my Volvo Penta engine manual and the dealer for my 2016 5.7 320 HP. Not all may apply to your particular engine or year. For my engine I stay with the mineral oil until 50 hrs. then it changes to full synthetic and a dealer inspection. The manual also recommends a fuel stabilizer on every fill up if using ethanol fuel and of course for winter storage. Also, the 87 octane is ok but the higher octanes may contain the more useful additives and engine may have a bit more power. I'm guessing it's user choice on a stabilizer each fill-up but that was what the manual suggested. If 87 was my only choice I probably would for sure.

Using fuel stabilizer should be a higher priority when there's ethanol in the gas (E10), but simply having lower octane shouldn't affect the fuel's longevity. My manual also talks about 87 octane being just fine (I think the compression ratio is 9.4:1), but that the engine is computer-controlled and can advance timing to squeeze a little more power out of higher octane fuel.

Totally agree, no need for stabilizer in any octane fuel unless E10.

I use Seafoam on every 3rd fillup. Incredibly good stuff. I rarely run below 1/2 a tank before I fill. Occasionally I'll get to 3/4 empty, and always feel anxiety when I do, just one of my quirks I guess.

Seafoam stabilizes the fuel and keeps the system clean. Its also really good at removing any moisture from condensation. Our climate is pretty humid.

Of course, this has been with all my past boats , but I'll be doing the same thing with my 240 this spring. We're getting REALLY anxious to get her on the water!

My routine and one comment from a long time Merc mechanic.
My routine is to make the last two fuel ups of the season premium non-ethanol treated with marine Stabil. Otherwise, I fill the boat with pump premium gas which is 93 octane with ethanol.
My boat mechanic recommended that I use premium gas for its "quality". The thought is that premium is a more refined gas. Now, please allow me to put on my petro additives hat... back in the day before ethanol was added, I was told by highly trusted mechanics to use Amoco premium gas as it would leave almost no deposits in the induction system. This was also supported by mechanics that worked at Ethyl that oversaw the testing lab and two old timers I knew. Is it worth the cost??? Only time will tell.
Chris

Your old if you just said Amoco.lol
I worked at one.lol yes best gas back then. Now gas is watched pretty close. I would just use a good top tier gas you pick your octane. I can get 87or89 ethanol free here so that is what I use or our 93 is also E free. Just pay another $.50 per gal. I never noticed much of a performance change between them. It drinks it like koolaid so why pay the extra if it's out of my way to get it.

These days, "premium gas" can mean two things - high octane gas, or top-tier gas. High octane is mostly slightly longer hydrocarbons so it doesn't ignite as quickly, while lower octane has more shorter hydrocarbons like pentane or even butane in winter blends. Top tier is an industry designation for meeting certain additive package and refining requirements, like low sulfur and cleaning agents, etc. For a boat, top tier seems like a great idea but I wouldn't pay any extra for high octane unless the boat's engine can make use of it.

John

Well said John.

I'm old, but not that old... (47). It would be great to hear from someone with a refinery or fuels blending background. For us in the mid Atlantic region, I was told that Amoco premium (93) was the only pigged premium fuel piped into the region. By pigged, that means a rubber plug is put in the pipeline to keep products distinct. Anyway, that was almost 20 years ago, and I can't imagine how adding ethanol impacts quality gasoline, or if any gas grade is pigged anymore.
I will say this... I use treated av gas in my lawn equipment and generators because they sit through the winter. Never had a problem. Love that 100 octane light lead gas. Great stuff.

Non-ethanol gas for me always. It's expensive but I don't worry about adding treatment.

I have quite a bit of experience with props after last seasons experimenting. I'm still not pleased with my decision. I actually went faster with the 4-blade then the cobalt reccomended 3-blade - it;'s weird, the boat seemed to have less vibration with the 4 but seemed to "like" the 3 better.

Hard to explain. I'm still looking. I also mangled a prop in the process... did I ever post that pic?

No you didn't. Have no idea what you even ended up with.

I went with the factory recommended 3-blade form volvo penta... after switching back and forth a few times.

I was getting 51 mph with the 4 -blade at WOT with slightly better holeshot and less vibration on the way up. Switching back to the 3-blade I was topping out at 49 at WOT... but I don't know, it felt better to me. there was a little more vibration in the 30's but it was weird, the wake looked cleaner and it felt like she turned better. The 1-2 MPH didn't mean much to me.

I think I'll end up getting the SS 3-Blade this year but boy am i glad I didn't have it on when I visited a nearby lake. I was launching into pretty big rollers on a launch I'd never used - bizarre local spot, real narrow community street that dumps onto a crazy slippery launch. Posts and railroad ties around and underneath. Storm was coming in and I wanted to get the boat on the lift. coming off the trailer and I was rocking pretty good with the prop trimmed down just enough when a ridiculous wave hit the stern as I backed into it. threw me up and down hard enough to crack the skeg. Prop was completely mashed... this was the original prop the boat came with that had some missing chunks to begin with but Oh My God. I've never seen a prop this mangled.

I was just looking through pics and I can't find the prop pic but here's the new prop with the cracked skeg:


If I had a SS prop on who knows what I would've done to the drive. I'm no rookie at this either, just plain 'ol dumb luck. I could've done the same thing 100 times and it never happen again. Eventually I'll get the bottom replaced but It's really only a reminder of patience to me at this point.

Interesting. If you had stainless on you never know nothing may have happened? Or? Well good luck on your prop search.