Diesel Cruising RPM

[SailingCal21]

I've a Universal 5424, three cylinder 24hp on my 1981 O'Day 34. The maximum RPM is spec'ed in the owner's manual at 2800 rpm with a suggested average cruising speed of 80% (2200 rpm). Being a conservative sort, and not having much background with diesels, I've typically cruised at 2000 rpm. Would it be better to cruise a diesel at 80% of max rpm or is my self imposed 2k limit better for the life of the diesel?

 

[Jim]

Yes 80% is better

the extra exhaust gas pushes the crude out of the mixing elbow.

 

[RAD]

I sometimes run my Westerbeke 30

Like its a race car engine cause I read that its a good thing for diesels, most of the time I idle out of the marina and shut down after setting the sails and then idle back in so when I'm not sailing I've gotten into the habit to rev her up

 

[Rich Stidger]

I agree with Jim, 80% is better, and......

my Volvo east coast tech rep recommended that each time (or frequently) that you run your engine that you run at WOT for 10 minutes.He claimed that a short high-speed run kept the engine clean and gave you the assurance that the engine was indeed capable of this performance in the event that an emergency required it.I have always do this for the last 9 years and have observed no build-up in the exhaust elbow. I still have the original installed.

 

[larry w]

whip it good

Engines like to work; run it hard and often.

 

[sailaway78]

80% is best

Diesels like to work hard. Run it at 80%, and it will live for a very long time. Running it a lower RPM will carbon up the exhaust elbow, and cause problems in the future. Also as previously suggested, run it wide open from time to time for a few minutes. This will clean things out, and also give you advanced warning when the prop or bottom needs some attention.

 

[SailingCal21]

Thanks, I'm glad that I asked.

What would be the failure modes of running a diesel at its max rated RPM? At such low RPM would it be just advanced wear over time and possible overheating? Or as in gasoline engines would it lead to a catastrophic failure such as bent valves or crank shafts, cracked pistons, etc.