Just purchased a 97 Powerquest Vyper and I changed the oil before winterization. I decided to switch to synthetic Mobile One due to hours (430) and thought it would help with longevity of the engines. Now, though I have a performance boat, I generally do not beat on it. 3200-3400rpms is where I like to be. Once a month I may push her over 4k but that's it. Never WOT. So, based on my habits, did I make a good choice? Will it hurt the engines? Mercury is so adamant on their labeling of recommended fluids I want to make sure I didn't do anything wrong.

Mobil 1 is good oil. I switched to it in my 502mpi's shortly after buying my boat. The oil consumption was cut in half. You should be running 15w-50 in a boat.
With the driving habits you posted, I doubt you need synthetic oil. Merc recommends their oil so they can sell more oil. Mobil 1 is better.

Now quit driving your boat like Miss Daisy
WOT for a few minutes at a time isn't going to hurt anything and it may actually tell you if you are propped correctly.

I figure one person would call me Nancy or Daisy. LOL I just bought the ol' PQ a few weeks ago, a small upgrade from my 24 Baja Outlaw! I tend to drive more "tame" because I usually have 3 kids on board, all under 8 years old and my boy being 15 months old. Hence why bigger boat with amenities. But I am very very anal about maintenance. So I have done oil and filters, doing impellers, bellows, gimbal bearing and u joints this winter. Plugs after I burn fog oil off in summer.

congrats on your new vyper...pq are nice,solid boats

Griff is correct, Mobile 1 15W-50 and mine doesn't burn hardly a drop. 1999 502 MPI's Now if we could only get Wal Mart to start carrying the 15W-50 large bottles again!!!

Oil Myths, I hear them all the time.....after all I am a regional Valvoline Sales Manager.

Read here, good stuff

http://www.valvoline.com/car-care/motor-oil-myths/

Congratulations on your purchase!.......As others have said I wouldn’t worry about switching oils. For the record I changed from the conventional Merc. Oil 25w-40 to there synthetic blend 25w-40 at 400 hours with no problems other than after a long WOT run the oil pressure won’t drop temporarily as low at idle than it did with the conventional oil. I know the synthetic blend Merc oil is not the same as some that are 100% synthetic but it is still rated a real good oil by Hydro Cruiser in the oil threads on here. I have about 650 hours on my 502 mpi mags and they still run perfect with no signs of decreased performance/more oil usage, and that is with frequent 4900-5000 rpm runs by me for the last 400 plus hours. Just maintain em’, change the oil often, don’t hit the sticks hard till your on plane and the engines are fully warmed up, and watch/replace your exhaust riser gaskets and you should be good for a while.

Welcome to the PQ crew. I love mine. I also run Mobil 1 in my 502 MPI. And it dosent use a drop and i just turned 350hrs.

All oils are not the same. Mercury uses bel-ray oil which is a low quality oil. I went with synthetic in my Durango and only used a 1 1/2qts. in 25,000 miles. Amsoil does have some of the best products in their oil. I am also an Amsoil dealer. If interested , pm me.

I did extensive research online about synthetic oil use in boats back when I first got into boating. After all the red tape the most experienced boaters in the checkmate forum I had been on at the time made these points.

1) Boat specific oils such as quicksilver have additives to protect the engine against the harsh corrosive environments boats are submitted to.

2) Mobil-1 and other car specific oils do not have these additives and therefore do not protect against internal engine corrosion if you were to accidentally get some sea water in the crank case as the oil will break down quickly.

3) If you do want to use synthetic oil they advised me to go with quicksilver, or amsoil. this is only more info to help you out so if I am wrong it is based on information i was given.