Safe RPM

[craigman]

Fellas,
i'm almost done with my very first boat, and getting it ready for the spring.
It's a 1971 Reinell 15' trihull with a 85 hp Mercury on it.
What is a safe cruz rpm and max rpm? The boat didn't come with any manuals so that's why i'm asking. I don't want to hurt the motor by over rev'n it.
Thanks for any help for a newbie!

Craig

 

[Moody Blue]

Re: Safe RPM

WOT rpm would be 5200. Cruising RPM is whatever you want it to be. Best fuel economy is to keep rpms just high enough to keep the boat on plane. At WOT it will consume, roughly speaking, 8.5 gallons per hour.

 

[craigman]

Re: Safe RPM

Holy cow! 8.5 gallons in an hour!
I'll be sure to keep the speed down!

 

[Moody Blue]

Re: Safe RPM

Yeh, rule of thumb (very approximate) is to take 10% of the rated HP and that is the fuel consumption at WOT. Of course there are many factors at play but this will give you a general idea of consumption. Knock the throttle below 3/4 and you should see almost half the consumption.

 

[craigman]

Re: Safe RPM

Thanks Moody!
I'll keep her now!