Changing RPM's

[Studman]

A mech. told me today that I should never run the motor/drive at a set rpm. That I should change the rpm's every 5-10 mins
That it wasn't good to run at a set RPM for a long time
any truth to this ?

I know that in a new motor you should change rpms during break-in but a motor / drive that is 19 years old?

 

[IanBat]

Only if the revs you are running at are at not loading the unit up. This mostly affects diesels running at low revs.


---
I am here: http://tapatalk.com/map.php?bngmbc
Sent from my iPad using Tapatalk

 

[IanBat]

And even then I would not be changing revs every 5-10mins. All I would be doing on a long run would be lifting engine revs up to load the motors up every hour or so for 5 -15 minutes.
Altering your revs every 5-10 minutes is only going to make you good friends with your local fuel supplier


Sent from my iPad using Tapatalk

 

[sea salt]

Ask your mechanic if you should screw around with the governor on your genie. After all, it's set to run at steady rpm for hours on end.

 

[Studman]

First off he is not MY mechanic, I said A mechanic and second I don't have a Genie. If I did I would wish for a bigger boat and free fuel

yea it did sound right to me either

 

[390x]

I'm pretty sure I wouldn't listen to anything that guy says.

 

[carterchapman]

His name wasn't w!ngless was it?

 

[northern]

Have 1750 hours on my 454s. Run them for hours at constant RPM. Does not seem to effect them. Longest run at 1800RPM was 130 knots that was about 16 hours. Most of the time run them at 1200 to 1400RPM for 10 hours or so. Have run them at 3800RPM for two hours but that is a lot of fuel. Needed to make a crossing before a storm. Used to run two stroke outboards for several hours at constant RPM they seem to do fine. Piston planes run at costant RPM for long times.
No idea if this is all bad or good.

 

[Gofirstclass]

The CAT tech who did my engine surveys said it's a good idea to follow the 80/20 rule when running the CATS---run at 80% throttle 20% of the time, whether on long runs or not. That makes sure that they get up to a proper engine temp.

I try to do that. Usually we're running about 1000-1100 rpm's and that's about 12kts. About 20% of the time I'll boost them up to 1750rpm's and that puts us on plane at around 22kts.

 

[Jimmy Buoy]

I've only heard this apply to an gasoline engine's break in period. I know you're talking about your mains, but my Westerbeke genny spins at a constant 1800 rpm by design. That backs up my assumption.

 

[390x]

The only two rules I'd give with a gas engine, after it's broken in, are running it at idle will likely make carbon build up on the pistons and valves, and running wide open will wear it out faster. There's nothing wrong with running them at cruising speed or less. Obviously common sense should play a part here, and knowing that running it at an rpm where its trying to plane but can't quite achieve it is hard on it as well.