Jeff,

If you get 3000 hours on your 5.7 Merc without a rebuild it will be extra
ordinary. Because boat engines are typically run at a much higher percentage
of max power than car engines, they typically need rebuilding as early as 600
hours.

I have a business partner who is a long time Merc mechanic, and former boat
dealer. When I bought my power boat new in 1997, he warned me that 600-800 hours
was what I could expect based on his experience. Right now, I'm still under
200 hours TT, so don't know yet if he's right.

Obviously there are a lot of variables that affect engine longevity including
the two biggies: Not running full throttle all the time, and properly winterizing.

YMMV,

Don W.


Messing In Boats wrote:

I've been using Mobile 1 in my 5.7 Mercruiser since I bought it with 211
hours on it. I use the green top 10-30W variety which is supposed to be
for older motors. I believe part of the reason Merc doesn't want you to
use it is because they don't sell it. Their pitch is similar to other
fluids for their equipment.

I change every 100 hours (three times this year, I'm happy to say!) and
use a WIX/Napa gold filter. Ask me in 3000 hours whether I was glad to
have used synthetic....

Jeff