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

That's why I stuck out my timetable so far; I figure I will have this
and a lot of other things figured out by then and will know what I
should have done.

I am hoping for 2000 hours though. I change every 100 hours and run the
boat at hull speed, about 1800 rpm, which I believe to be a lot kinder
to it than up on plane at 36-3900 as it was designed for.

What does your buddy say about synthetics?

Jeff

Jeff,

I haven't specifically talked with him about synthetics, but there was a
post a while back from a guy who had used synthetic oil in his 5.7L Merc
and had some kind of premature failure. The subject was " Mercruiser Motor
Failures" from Feb 2003. You might want to search for it on Google and read
his post.

Also, if Mercury specifically doesn't recommend something I'd think it is likely
because they've seen some problems, and not because they just haven't tested
it.

YMMV,

Don W.



Messing In Boats wrote:

That's why I stuck out my timetable so far; I figure I will have this
and a lot of other things figured out by then and will know what I
should have done.

I am hoping for 2000 hours though. I change every 100 hours and run the
boat at hull speed, about 1800 rpm, which I believe to be a lot kinder
to it than up on plane at 36-3900 as it was designed for.

What does your buddy say about synthetics?

Jeff