Need for Speed

Hello Fellow Tuggers!

I have a 2025 R31 with Volvo Penta D320. There are times like getting to a fishing spot that I would like get their as soon as I can. I recall the RT guys saying 2800 RPMs all day long. Anyone have experience pushing the Volvos to 3000 or 3200 RPMs for extended periods of time? Will the higher RPMs shorten engine life.

Thank you,
Paul

R-29CB D4-320. I can get 3480 max RPM at WOT. Coolant temp rises from a normal 171 to about 176. I don't run it long at this speed (usually less than 10 minutes) but I do it every once n awhile to test systems etc. My normal cruising RPM's are somewhere around 1800 and the engine just hums along, burning little fuel. I think if I was looking for more speed, I might consider an outboard engine.

I have always lived by the no more than 80% of wot rpm for continuous duty on diesel engines. Something else to consider is the D4-320 is the highest HP output of the D4 lineup. So I would guess the engine is already under loads closer to its limits. But if you aren't looking for a super long life on the engine then you might be fine. If I had to throw out an educated guess, you might be able to run that engine at or near wot for 1500 to 2000 hours, but I doubt it would ever make it to 5000.

Determine max RPM at WOT. Then run your engine at 80% of that RPM all day long. With regular maintenance your diesel engine will last 1000s of hours.

I thought the guidance was 90% max RPM or 80% max power? That’s my typical fast cruise speed, which on my R29-CB is 3150 to 3200 depending on load.

From my experience max rpm and WOT can vary based on many factors that effect engine loading. Often the WOT ends up being lower than the manufacturer specified max rpm. As to best rpms to run your engine at continuously, I think these numbers are based on different manf specs and different opinions. So there might not be any one "correct" answer.
In general lower rpms should result in a longer life span. Similar to more often oil changes.
I have heard stories about charter sailboats that have thousands of hours on engines at WOT, but I don't know if those stories are true or if those engines are designed to handle it.

Add the engine load percentage to your Volvo Penta engine display. RPM and WOT are a proxy to this, but with the smart digital controls these engines have you have the actual data. Current/wind/weight on the boat will all impact RPM, you could be at 50% of your engines WOT RPM in some cases but still be at 80% engine load, or the reverse. If you have ever done research into adjustable pitch props, you will learn that engine load percentage (e.g. through exhaust temp and GPH) is the only thing that really matters as you can keep RPM constant.

Aim for 80% to 90% depending on your preference. The engine has an R5 rating, which is 100% load 1 hour out of every 12 hours.