A good operating range for a merc 115 a correctly pitched prop

" I've got a 1986 merc 115

" I've got a 1986 merc 115, with a 17 pitch prop. At full throttle with 4 passengers I get 5400 RPM's.. the boat it's pushing is a 21 foot alum. Starcraft Cheiftan. It seems to jump right out of the hole, doesn't bog, and moves about as fast as you ever really want, givin the hull (most of the time I'm out in the chop).

Before I put a tach. on, I swore that I would have to pitch the prop up, the merc just sounds different than the Johnsons I'm used to, but now I'm wondering if it has to be pitched down a notch- is running at 5000 RPM's a bad thing? Any input would be great, I'd love to find someone who has a similar set-up,

Jon "

In my opinion you are running

In my opinion you are running at the correct top RPM for that engine. The IL6 MERC will run fine in this range. When you may see problems is when you over prop and possibly detonate a piston. If you go down a pitch as you suggest you will turn more RPMs and probably lose efficiency. If you go up a pitch you will lose RPMs and lose some acceleration.
Tom

" Tom,
Thanks for the

" Tom,
Thanks for the input, I should've included something about this in my post, but one of the things that made me concerned about the RPM range is that I think the spark advance is triggered at 5400 RPM's; I was figured I should be running just a little above that for correct performance.. If you have anything to add, please do drop a line,

Jon "