I have 2001 500HP carbs. I heard synthetic oil should not be used in hp500'swith the roller cams. However in 99 they upgraded the valve springs and exhaust and was wondering about the rest of the valve train.
So, should I use synthetic oil in these engines?

Hell yes. Merc synthetic blend or a Mobil 1 20w-50. Or Valvoline 30 w synthetic.

Wannabe

Whiplash - What is your honest thoughts ?

I got the boat last year and immediately put in Amsoil synthetic, as I had in my previous boats. However I've never had roller cam engines. At the Buffalo Poker Run this past weekend I was talking with someone who has 1995 or 96 500's and he had a flat spot on a cam due to the lifter and engine shop told him it was because of the synthetic. I had heard something of this issue before but never though about it without having roller engines till now. I know Merc Racing updated the 500's in 99 but unsure if anything with the cam and lifters.

Teague started that 'analysis' many years ago when he did tech column for Hot Boats.

Anyway, the flat spots on roller cams are almost always due to the springs not keeping control of the lifters. More spring pressure and better springs fix that. Which Merc ended up doing. Obviously, engine shops did that right away when these engines came in with problems. Flat spots are not just a synthetic oil issue...it happens with all types of oils too..again, because of lifters not being controlled. 'Soft'er cam cores can also do this more, but yet again, it's the lifter being out of control.

Just my 'nobody' opinion and experiences.

Oh, and guess who has been driving the 'Amsoil' race boat for ever and ever, with roller cams, and I'm guessing Amsoil too ? Teague. LOL.

Actually Harley Davidson made those claims before Teague about roller lifters sliding on the cam lobes when using Syn oil. Well after years of that HD came out syn oil. Mercruiser use to make claims syn oil is not recommended for their engines years ago. They merc did not make any claims of failures but listed it as not recommended. Well they have syn oil to after years of not recommending it. Anyways just posting some other info.

Teague posted some additional info about the use of syn oil in powerboat mag listed in the tech column "Rebuttal _ _________)" forgot the header of it.

Synthetic oil seems to be the scape goat for an underlying issue. Harley Davidson being the #1 abuser. I ride the heck out of our 3 Harleys (and work part time at a dealer) and never had an issue with Amsoil, but there are some dealers out there that blame everything on any synthetic,,,except for theirs.

I have been running synthetic in my HP500 for 14 years with NO problems . http://www.amsoil.com/shop/by-produc...50-racing-oil/

OK lets think this through. The synthetic oil is so slick that it does not let the rollers turn? If that was the case with oil being that slick it would be most unlikely that the cam could get a flat spot from a no turning roller.
Hum?