Dean Ferry

Thanks guys, great info. I'll be in the bilge this sunday!
MD

blue thunder

It depends on your driving habits and what temp the oil is seeing when run most often. If the oil stays around 220* or less, from my experience, 100hrs is fine. If the oil gets to 260*+ regularly, I would say 20 hrs is appropriate. Oil looses its cushioning effect from contamination and heat. If either one are suspect, more changes are better.

BT

Gary C

I change my oil every season or 50 hrs which ever comes first. I use 40 wt Castrol. I've been doing this for longer than I care to admit and never had a problem. Of course I have always had stock motors. Plus I don't run hard. Now I have a 454 mag carb. If I had an hp 500 I would probably go with 20-30 hrs.

Milord

I have bone stock SBC's. I change the oil once a season which is about 100 hours. No need to change it more often with these motors and the type of boating I do. If it was a poker run boat I would probably change more frequently.

blown formula

I always change about every 60 days during the spring-summer. That means I have fresh oil in it when winterized, believe it or not some leave the old stuff in all winter!!

obnoxus

Every 20-25 hours ,,, Royal Purple straight 40 weight racing synthetic, and a Mobile 1 M1-302 filter.

OPIE272

Jua thought from an "old " filter man!!!!!!!!
When I worked in a manufacturing plant MAKING FILTERS, Our brand name filters that failed our standards that would still pass FRAM's specs became Fram filters.
My 2 $ worth
I wouldn't put Fram filters on my kids go-cart.
Hope I didn't offend anyone but if my rejects would pass another MFG. specs. I wouldn't run anything they made

Tinkerer

I use 40 wt VALVOLINE RACING oil and the NAPA racing filter.
I change the oil twice a year. About every 40 hrs. I don't run it that hard.

Dennis Moore

The March Family and Performance Boating Magazine will have an article on oil filters. There is something that most people don't know about the Chevy automotive filters. Because the Chevy automotive engineers were aware that oil will run out of the filter if the engine sits for a period of time they mounted the oil filter in the vertical position. Almost all other engines have the oil filter mounted at an angle and need an anti drain back valve in the filter. Without an anti drain back valve the engine will have to refill the oil filter with oil every time the engine is restarted (zero oil pressure to the engine while the filter is being refilled). Chevy automotive/truck oil filters do not have an anti drainback. Some Mercruiser engines have the (remote) oil filter mounted upside down and some are on the side. These engines need oil filters with an anti drainback valve. The only Chevy oil filters that I have found with the valve (after cutting open many filters for the magazine article) were the Mercruiser and Fram HP series filters. You should use one of these filters for any Mercruiser that
doesn' t have the filter mounted vertically. Many other things in the March issue that are interesting, be sure and read it!
Sincerely
Dennis Moore
FAMILY AND PERFORMANCE BOATING MAGAZINE

CAP071

I change mine about every 15-20 hours. stock Mercruiser filter and Valvoline VR-40 synthetic.