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-   -   How Hard To Push My Perkins (http://www.sailnet.com/forums/diesel/93515-how-hard-push-my-perkins.html)

MarkSailor 10-27-2012 02:50 PM

How Hard To Push My Perkins
 
This may be a dumb question, but that has never stopped me before.

I have a 1994 vintage Perkins "Perama" 29 HP inboard diesel, with about 1300 hours on it, in a Catalina 320. I think the engine was fairly well maintained by the former owner, and I have tried to be good about changing oil, filters, etc.

The question is, how many RPMs would you push this engine at cruise or for short periods when trying to clear other traffic, etc.? I usually cruise between 2000 and 2500 RPM, but wonder if I am being too cautious. I have a service manual for the engine, but it doesn't address this question. Any advice?

SloopJonB 10-27-2012 03:57 PM

Re: How Hard To Push My Perkins
 
Quote:

Originally Posted by MarkSailor (Post 939321)
This may be a dumb question, but that has never stopped me before.

I have a 1994 vintage Perkins "Perama" 29 HP inboard diesel, with about 1300 hours on it, in a Catalina 320. I think the engine was fairly well maintained by the former owner, and I have tried to be good about changing oil, filters, etc.

The question is, how many RPMs would you push this engine at cruise or for short periods when trying to clear other traffic, etc.? I usually cruise between 2000 and 2500 RPM, but wonder if I am being too cautious. I have a service manual for the engine, but it doesn't address this question. Any advice?

Don't your documents list a Max recommended RPM? That's the number you are looking for. A Perkins dealer should have it.

svHyLyte 10-27-2012 04:15 PM

Re: How Hard To Push My Perkins
 
Quote:

Originally Posted by MarkSailor (Post 939321)
This may be a dumb question, but that has never stopped me before.

I have a 1994 vintage Perkins "Perama" 29 HP inboard diesel, with about 1300 hours on it, in a Catalina 320. I think the engine was fairly well maintained by the former owner, and I have tried to be good about changing oil, filters, etc.

The question is, how many RPMs would you push this engine at cruise or for short periods when trying to clear other traffic, etc.? I usually cruise between 2000 and 2500 RPM, but wonder if I am being too cautious. I have a service manual for the engine, but it doesn't address this question. Any advice?

Mark--

While I am not familiar with your particular engine, I am with Perkins in general and of those I have been acquainted with, Perkins rates their horsepower based upon a maximum RPM which can be maintained for a short period, a few minutes, but a maximum continuous service RPM that is typically in the range of 75% of rated horsepower RPM.

For example, our 4-108 is rated at 50hp at 4,000 RPM but that rate can only be maintained for a few minutes. Our maximum continuous service RPM is 3000 which, on our yacht with our prop gives us about 7.5 knots is moderate seas. We typically run the yacht at about 2500 RPM which gives us a good trade-off between speed and fuel consumption.

FWIW...

jrd22 10-27-2012 10:09 PM

Re: How Hard To Push My Perkins
 
You'll need to know what the WOT (wide open throttle) rpm is supposed to be so you can determine if you are correctly propped/pitched. A Perkins dealer should be able to give you the correct max. rpm and the max. recommended cruising rpm (sorry, I'm not familiar with that engine). You should be able to run the engine at full throttle for 5 minutes or so if needed with no problem (if you have the right prop).

amarinesurveyor 10-29-2012 08:00 AM

Re: How Hard To Push My Perkins
 
The Perkins Perama M-30 engine puts out 29 hp at 3,600 rpm, that is your maximum rpm. Usually you can run diesels at 75 - 80% of maximum rpm all day long. That would be 2,700 to 2900 rpm. You should also be able to run at full throttle for short periods if everything is right (cooling system, clean prop, clean bottom, etc.).
Brian

caberg 10-29-2012 09:46 AM

Re: How Hard To Push My Perkins
 
My Yanmar hits a spot at around 2500 rpm where it just feels right. That's not very scientific--and I agree you should know your numbers--but ultimately I think you will find that your engine has a sweet spot where it likes to run.

TQA 10-29-2012 10:12 AM

Re: How Hard To Push My Perkins
 
The Perama is not a 'real' Perkins in that it is not one of the heavily built over engineered lumps of cast iron like the 4-108.

It was made by Ishikawajima Shibaura Machinery, Ltd, yup Japanese, and marinised by Perkins.

With almost any diesel the throttle position tells the governor what rpm to run the engine at. That could mean full fuel which usually gives a trace [ or more ] of dark smoke. I avoid running my engine at full fuel if I can because that is max load on the engine.

MarkSF 10-29-2012 02:12 PM

Re: How Hard To Push My Perkins
 
Am I the only one who runs the engine at the one rpm setting where everything in the boat stops rattling? That's 2100 in my boat.

SloopJonB 10-29-2012 06:26 PM

Re: How Hard To Push My Perkins
 
Quote:

Originally Posted by MarkSF (Post 940045)
Am I the only one who runs the engine at the one rpm setting where everything in the boat stops rattling? That's 2100 in my boat.

Even with a one lung Yanmar I experienced the opposite - there was one rpm where everything quivered - the lifelines were a blur. If yours is shaking pretty well all the time you should check your mounts, shaft alignment and so forth - it sounds like something is wrong.

Classic30 10-29-2012 09:04 PM

Re: How Hard To Push My Perkins
 
Unlike petrol engines, diesels (all diesels) are designed to be run under a decent load and relatively high rpms - even WOT - for long periods of time.

Long periods at idle/light load glazes the bore.


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