volvo md21 diesel RPM's

[ticomic]

volvo md21 diesel RPM\'s

I purchased a 30-foot lobster type boat last year. The Volvo MD21A runs like clockwork. The previous owner is a retired marine engine mechanic, worked most of his life on seagoing tugs and on those in the Québec City harbour. He insisted I should keep the RPM's at 1500 , and should never go higher than 1800, even then only for short periods.

The book gives a 61 hp rating at 4,500 RPM, and 45 hp at 3,000 RPM. I used the motor every day for 3 months without the slightest hint of a problem. The TWO
temp guages agree at half the scale. Would these low revs be a little overcareful?
At 2,000 RPM, which I accidentally reached for a few minutes, she actually goes a bit faster than at 1,800, so I presume hull speed has not yet been reached. Being a flat-bottomed hull, she moves forward very easily, and stays level.

Any thoughts on this limitation of RPM's?

Merci!



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[Steve_N]

Re: volvo md21 diesel RPM\'s

According to the Volvo blurb 'the engine (MD21B) is delivered to be used for pleasure boats adjusted to 4500 rpm'. It's a marinised Peugeot-Indenor XDP4/90 car engine so those revs wouldn't seem excessive for the engine itself. I've recently purchased a boat with an MD21B and it is indeed governed to 4500 by the newly-replaced injection pump and has a 5000 rev counter on the Volvo panel.

On the other hand I don't think I'll be using those revs much: with a 1.93:1 reduction I'd guess the prop would just be making froth at those kind of revs..

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[DonaldMacdonald]

Re: volvo md21 diesel RPM\'s

Did you get any answers to this. My MD21a appears to be restricted to 3000 rpm.
Donald

 

[jamesyboyz]

Mine revs to 4200rpm at 9.5 kts

 

[macd]

Re: volvo md21 diesel RPM\'s

Did you get any answers to this.

Welcome to the forum, Donald. ticomic last visited the forum over 12 years ago, so I doubt will be responding. (You can easily check this for anyone by clicking on the username, which will reveal a precis of the poster's activity.)

But I'm sure others will be along with their knowledge and experience. My three penn'orth is that you should absolutely not limit your engine to 1500rpm. Diesels, and particularly automotive diesels, positively benefit from being worked. The engines the previous owner was used to probably maxed out at 1000rpm or so, and are a different kettle of fish.

Incidentally, do you think your engine is actually governed to 3000rpm, or is that just all it will reach? If the latter, in neutral, or underway and in gear?

(I'm of the clan Campbell, by the way, but have only visited that place for the climbing. I wish you well.)

 

[pvb]

Re: volvo md21 diesel RPM\'s

Welcome to the forum, Donald. ticomic last visited the forum over 12 years ago, so I doubt will be responding. (You can easily check this for anyone by clicking on the username, which will reveal a precis of the poster's activity.)

But I'm sure others will be along with their knowledge and experience. My three penn'orth is that you should absolutely not limit your engine to 1500rpm. Diesels, and particularly automotive diesels, positively benefit from being worked. The engines the previous owner was used to probably maxed out at 1000rpm or so, and are a different kettle of fish.

Incidentally, do you think your engine is actually governed to 3000rpm, or is that just all it will reach? If the latter, in neutral, or underway and in gear?

(I'm of the clan Campbell, by the way, but have only visited that place for the climbing. I wish you well.)

DonaldMacdonald was last online 13 years ago, so I doubt he will be responding to you. (You can check when posters were last online by clicking on their username.)

 

[macd]

Re: volvo md21 diesel RPM\'s

DonaldMacdonald was last online 13 years ago, so I doubt he will be responding to you. (You can check when posters were last online by clicking on their username.)

My bad! (And humorously put by you).
I shall now take my embarrassment somewhere dark.

 

[pvb]

Re: volvo md21 diesel RPM\'s

My bad! (And humorously put by you).
I shall now take my embarrassment somewhere dark.

Sorry, but I couldn't resist it!

Seriously, these phoenix threads are a bit of a problem.

 

[macd]

Re: volvo md21 diesel RPM\'s

Sorry, but I couldn't resist it!

I, too, can resist anything but temptation. (And plagiarism, obviously.)

Seriously, these phoenix threads are a bit of a problem.

True. The older I get, the more I envy them...