No RPMs past 80% max - Volvo Penta

[tranmkp]

Ill post here simply it applies to marine diesel. Ill use Volvo Penta as an example. I am told by the Volvo reps that I should not run engine past 80% max rpm (4000). What Im trying to understand is WHY? How different is a boat in the sea (smooth water) different that a truck pulling a load (uphill?) - at 100% i see no smoke no extreme fuel consumption. I do see and increase in temp but that is a different animal altogether. Am I going to blow seals? Spin bearings? I know it will keep the VV turbo clean. Can this be explained to me?

Thanks

 

[racer12306]

Complete wild shot by me.

Could it be to minimize the risk of over reving if you get in rougher water where the prop may leave the water? Shouldn't be going crazy on rough water anyways, just a though.

 

[wwillson]

They are trying to limit sustained high EGTs.

 

[SeaJay]

Old wives tale. I wouldn't max out the RPMs on long trips, but running for some time at max RPM shouldn't kill the motor.

Best reason to run at 80% or so is fuel savings and efficiency.

 

[wwillson]

Old wives tale. I wouldn't max out the RPMs on long trips, but running for some time at max RPM shouldn't kill the motor.

No, it won't kill the motor, but sustained high EGTs will shorten the life of the motor. If it doesn't matter to the owner how long the engine lasts, then by all means, run it wide open for long periods.

 

[Rand]

A boat is unlike a truck.. the hill eventually has to end in the truck
Boat can run 100% for hours.

Pretty sure no one thinks running a truck in a mid gear at redline for hours is great either.

For short periods no issues Imo.

 

[OilUzer]

If your car or truck gets near max RPM when towing uphill or not, you need a bigger engine or a diesel. I keep my cars or trucks under %70-75 even when towing ... Typically well under %70 RPM unless for a very short duration.

As far as boat, I would do the same. %80 sounds reasonable. As mentioned my boat made a nasty sound when the prop came out of water. No load and RPM jumps. I would buy a bigger boat or upgrade the engine.

 

[tranmkp]

Thanks for all the reply's.
Boat is inboard. semi planing so not much cavitation. The EGR has got my attention... I have no temp gauge so dont know. Can I know a little more about EGT and Diesels? How besides lower rpm or load is EGR controlled?

 

[tranmkp]

I did a little google search and have a better understanding about what EGT is and does... Volvo Penta does make a temp gauge plus there is a fitting on the turbo inlet side. Did read about how some truckers drive by the EGT. IM not into installing methanol injection.