Motor over revving? Due to colder temps?
Motorhead
Posted 10/5/2012 7:12 AM (#589097)
Subject: Motor over revving? Due to colder temps?


My motor never ran over 5900 or so all year and yesterday same load as usual it ran up over 6k rpms but the rev limiter never came on either? Was it just the gauge off or do motors tend to run higher rpms in colder water/air temps?
Shep
Posted 10/5/2012 4:52 PM (#589227 - in reply to #589097)
Subject: RE: Motor over revving? Due to colder temps?





Posts: 5874


cooler air temps mean denser air and more HP. My Opti's always ran like scalsed cats in the fall/winter. 1-200 RPM's can be typical.

Water is harder, too. You should see some extra MPH as a result of the two.
VMS
Posted 10/5/2012 5:24 PM (#589236 - in reply to #589097)
Subject: Re: Motor over revving? Due to colder temps?





Posts: 3511


Location: Elk River, Minnesota
Yep!! Water is denser, so your hull probably is riding a little higher out of the water while on plane as the prop can hook up a bit better.

Shep is right on...cooler air temps and lower humidity mean Horsepower... 100 to 200 rpm increases are common. My 90hp johnson does the same thing... I didn't overrev, but I did gain speed at max rpm.

Steve
Guest
Posted 10/7/2012 10:59 AM (#589457 - in reply to #589097)
Subject: RE: Motor over revving? Due to colder temps?


thanks that must be it. I never knew that. It ran to almost 6300 rpms and typically hasn't gone above 6k.