Don, your opinion of this

[Flipping57]

Don, what is your opinion on this subject?

http://www.bbcboards.net...-rpms

[EuropeanAM]

From my response on that post:

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by TRCM &raquo;</TD></TR><TR><TD CLASS="quote">I was told by someone on this site who KNOWS what they are talking about, that you should prop your boat to run in the top end of the recommended rpm range.

That being said, that does NOT mean you have to run at those rpms all the time.

You don't want to prop your boat so that you can easily over rev the motor, and you don't want to prop it so you can't achieve max rpm (or very close to it).

I probably spend 50% of the time right around 4700-5000 rpm on my rig, and it's propped to hit 5600-5700 right now.

I was also told by the same person to 'air it out' for a few minutes every time out to help keep the carbon cleaned out.</TD></TR></TABLE>

"That" person was asked to chime in.

There are many factors to consider on this subject. As far as "will it hurt the engine to run it at the top of the Recommended RPM Range":

If the engine is properly lubricated, cooled, maintained, broken-in, IN GEAR UNDER LOAD and SET UP, today's engines are designed to withstand EXTENDED WOT RUNTIME, within the maximum RPM recommendations. ALL two stroke engines (carb, DFI, or EFI) have, for the majority of my "short" career, been manufactured to far stiffer tolerances and manufacturing guidelines (as apposed to your average automobile engine).

Most manufacturers perform EXTENDED RUN (in some cases... literally 24 hours a day at WOT) testing of their engines at these RPM's during the R&D stages. Data collected during this time (and results seen regarding internal "wear and tear") is used in helping to compute the "safe" Maximum RPM specification.

Additionally, Marine Engines are "fully loaded" when in gear and properly set up. This is very different from the "automobile", which is commonly under less than a "30%" load factor (often WAY less).

That being said, most outboards will attain their best fuel economy, and CLEANEST COMBUSTION in the mid-range (3500-4500 RPM) range. In and of itself, maintaining a large majority of your runtime in this area can reduce carbon deposts, and help to increase the lifespan of your engine.

However... if your intentions are to "putt-putt" around the majority of the time, you'd be wise to consider a 4-stroke engine. Today's 2-strokes ARE meant to be RUN.

[Flipping57]

Thanks Don