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Old 19-12-2005, 15:41   #1
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Normal operating rpm

I have been unable to find a recommended figure for a "recommended" maximum rpm at which to run the motor during "normal" use.

The engine in question is a Volvo Penta 2003 (model, not year).

The Instruction book that I have downloaded quotes the maximum operating rpm as 3200 (producing 28 hp).

I'm guessing that there will be a percentage of the max revs that is recommended for long periods of motoring, and a higher percentage that may safely be used for short periods of time.

Because I cannot find any figures for safe rpm, I have been fairly conservative and stayed below 2200 rpm, but It would be nice to know if I could safely crank that up some without risking shortening the motor's life expectancy....

Anyone have any hard and fast figures or rule of thumb calculations?
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Old 19-12-2005, 15:58   #2
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Old 19-12-2005, 16:31   #3
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I looked at the power curve on Volvo's site. I think 2200 is to low. I'd run it between 2500-3000
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Old 19-12-2005, 17:44   #4
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80%

is the standard used for normal operation. If the maximum RPM is 3200 then the operating RPM would be in the vicinity of 2500 to 2600.

Jim
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Old 17-08-2020, 09:58   #5
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Smile Re: Normal operating rpm

Today, after repair of a leak in the return fuel line, bleeding, etc, by the Volvo agent, the motor was ticking like a swiss watch. The mechanic told me to accelerate full throttle in neutral. I asked: are you sure? and he said yes, lets give it a try. I did, it went up to 3200 rpm without smoke (and did not explode). I normally cruise between 2200 and 2800 rpm. It is a 2003 B (1991) raw water cooled.
OLD VOLVOS NEVER DIE !
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Old 17-08-2020, 10:16   #6
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Re: 80%

Quote:
Originally Posted by Jentine View Post
is the standard used for normal operation. If the maximum RPM is 3200 then the operating RPM would be in the vicinity of 2500 to 2600.

Jim
Your 80% is closer to a maximum sustained than a “normal”
For instance 75% power is usually a maximum sustained power for an aircraft piston engine.
However an engine will last much longer if not run so hard, the exception to that is if an engine is very much derated to start with, a seriously derated engine it’s not so bad to run nearly wide open, as wide open isn’t really “wide open” because it’s derated.

An automobile with a 6500 max RPM for example, 80% is above 5000 RPM, do you guys drive your cars in a gear that equals over 5000 RPM continuously?
Why not?
Then why would you do it in your boat? Do you think boat motors are “special” motors and that they are different than regular motors?

Low power operation, even for Diesel engine autos has a very great deal to do with why they last so long.
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Old 17-08-2020, 10:23   #7
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Re: 80%

Quote:
Originally Posted by Jentine View Post
is the standard used for normal operation. If the maximum RPM is 3200 then the operating RPM would be in the vicinity of 2500 to 2600.

Jim
Your 80% is closer to a maximum sustained than a ďnormalĒ
For instance 75% power is usually a maximum sustained power for an aircraft piston engine.
Actually percent power doesnít track RPM exactly, but itís not way off at higher RPMís
However an engine will last much longer if not run so hard, the exception to that is if an engine is very much derated to start with, a seriously derated engine itís not so bad to run nearly wide open, as wide open isnít really ďwide openĒ because itís derated.

An automobile with a 6500 max RPM for example, 80% is above 5000 RPM, do you guys drive your cars in a gear that equals over 5000 RPM continuously?
Why not?
Then why would you do it in your boat?
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Old 17-08-2020, 12:05   #8
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Re: Normal operating rpm

It's a natural, non-turbo, engine. Higher rpm won't bother it as much because the exhaust gas isn't that hot. If you keep the oil clean, it can probably run at 80% for the next 20 years.

The most wear is going to be the rings and cylinder walls. Excessive heat and dirt in the oil are the cause the most wear. Once the crosshatching wears (carries oil to the upper cylinder) the cylinder and rings wear fast. Before that time, new crosshatching can be honed in and new rings will give near new performance.
Pic is x-hatching in Detroit sleeves.
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