Cruising RPM for universal M25-XP

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Brad on Vashon

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Jan 27, 2012
65
Catalina 30 Vashon
first long cruise exposed some new issues-- like that I can barely make 5+ kts in slack water or less than 3 in a sloppy chop with an adverse tide. I have a clean two-blade prop.

My survey mechanic said I should cruise at about 2600 RPMS. In ideal flat conditions that is about 5.1 kts SOG. If I throttle up to full 3200' I can get over 6--Made for a very long cruise in south Puget Sound


Does this sound right? What are you using? What do you run your M25 XP at?
brad
 
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mortyd

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Dec 11, 2004
952
Catalina 30 easy living
don't know how hot it gets where you are, but i don't like to go over 2000 for a long time on long island sound in the summer. unless you want to make pasta in the cabin.
 
Bob S

Bob S

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Sep 27, 2007
1,774
Beneteau 393 New Bedford, MA
I generally cruise between 2300-2500. Sea conditions and bottom cleanliness dictate my speed at about 5 to 5.5 kts. I have a three blade prop.
 
Brad Woodward

Brad Woodward

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Nov 24, 2011
95
Catalina 30 San Diego
I generally cruise between 2300-2500. Sea conditions and bottom cleanliness dictate my speed at about 5 to 5.5 kts. I have a three blade prop.[/quote]

WOW I guess I am doing very well. I have a 1986 Catalina 30 with the M25-XP engine. I was told to cruise around 2000 RMP and not go over 2500 RPM for very long. I usually cruise around 18 - 20K and, in calm water, am doing 5 to 5.5 MPH. If I push it up to the 2200 RPM I get up to 6+ MPH but my fuel consumption goes up exponentially. I have the 2 blade prop too.
 
Stu Jackson

Stu Jackson

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Feb 26, 2004
22,783
Catalina 34 224 Maple Bay, BC, Canada
Brad W - under 2000 rpm is almost lugging the engine. Give it a workout, it can do much more. Fuel consumption "exponentially?" I've been running our M25 (same engine as yours, but only 2 hp less, and I added the 3 inch HX) for 13 years and get better than half a gallon per hour over all ranges of rpms, but usually do 2600.

You might want to consider going to knots, too, instead of MPH...:):):)
 
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mortyd

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Dec 11, 2004
952
Catalina 30 easy living
stu, maybe i have a faulty tach, but i have no problem doing 4.5 knots and running 160 degrees at 2000 rpm, which i consider ideal for long times; shorter times when i want to go faster, i do.
 
rpell1@msn.com

rpell1@msn.com

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Sep 25, 2008
464
Catalina 30 MKIII Varuna Boat Club
My 25xp has about 1250 hours. I average 5-6 knots at 2200rpm. With the least amount of prop garbage, I cannot get her over 2600rpm.......But, strangely I still get 5-6 knot average. Once the bottom starts to slime over, I can lose up to 2 knots, (usually by August) and it's time to "scrub". If seas get a bit heavy, (3-5 feet), I drop to 4 - 4 1/2 knots. All this with an average usage of about 1/2 to 3/4 gallon per hour. This is the most consistant and reliable little diesel I have ever seen. (Fingers crossed).

Happy Sailing.
 
Coriolisbc

Coriolisbc

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Jun 29, 2011
142
Catalina 30 Mk II Gibsons
2100 is where I cruise, at 5.5 knots in calm water, I have the 15 inch three blade prop.
 
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Brad on Vashon

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Jan 27, 2012
65
Catalina 30 Vashon
rpell46 said:
My 25xp has about 1250 hours. I average 5-6 knots at 2200rpm. With the least amount of prop garbage, I cannot get her over 2600rpm.......But, strangely I still get 5-6 knot average. Once the bottom starts to slime over, I can lose up to 2 knots, (usually by August) and it's time to "scrub". If seas get a bit heavy, (3-5 feet), I drop to 4 - 4 1/2 knots. All this with an average usage of about 1/2 to 3/4 gallon per hour. This is the most consistant and reliable little diesel I have ever seen. (Fingers crossed).

Happy Sailing.
Click to expand
Repell-what prop o you have?
 
Terry in Naples

Terry in Naples

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Aug 8, 2006
340
Catalina 34 Naples FL
I keep my prop and bottom clean using a "hooka" and scraper as needed. I can cruise all day at 2400 to 2600 and go along at 6+K in flat water. If a breeze is up and i need speed I raise a sail and many times get 7+ on the gps. I have a C34, 3 blade prop that came with the boat.
 
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mortyd

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Dec 11, 2004
952
Catalina 30 easy living
the gps gives you speed over the earth, not through the water. your 7 knots could be due to a six knot current behind you.
 
Brad Woodward

Brad Woodward

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Nov 24, 2011
95
Catalina 30 San Diego
Speaking of RPM's. I recently had to replace my tach/hr meter as the hr meter quit at 750 hrs. Catalina Direct wanted over $600 for a replacement. I got one from a marine supply store for under $200. It is a Stewart Warner. It has a dip switch on the back to set it for the type of alternator it is connected to. I couldn't find out what I had so I used the old tach to see what the RPM was at idle and played with the switches until I got it to read my idle RPM on the old one. I think I am in the ballpark but am not sure if it is exact. Anyone know how to determine what alternator I have? Looking for # of ploles and that type of stuff. I won't be at the boat for a few more days so I can't get to the manual to see exactly what info I need. I couldn't find any sort of markings on the alternator itself.
 
Stu Jackson

Stu Jackson

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Feb 26, 2004
22,783
Catalina 34 224 Maple Bay, BC, Canada
Brad, the easiest way to do it is to run the engine in neutral to WOT which should be 3000.
 
B

Brad on Vashon

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Jan 27, 2012
65
Catalina 30 Vashon
Stu Jackson said:
Brad, the easiest way to do it is to run the engine in neutral to WOT which should be 3000.
Click to expand
Stu-- I'm a little slow on the up take...what does WOT mean?
 
fox islander

fox islander

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Jun 5, 2004
241
Catalina 30 MkII Foss Harbor Marina, Tacoma, WA
Just returned from a cruise to Paulsbo...I keep it around 2,200. I was making 5.7 - 6.0 knts in calm and 5.3-5.6 knts in chop with a clean prop and bottom. M25 XP w/ a two blade prop.
 
Bad Obsession

Bad Obsession

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May 23, 2004
3,319
I'm in the market as were . Colonial Beach
I get about 5 knots, give or take a half of a knot for current, on a three blade prop. This is also pulling a hard dingy. The thing is that I am disappointed in my top end speed when doing the 2600 rpms. I think that the big issue with the design of the Catalina 30 is that you can only put a 13" prop on it. The catalina 34 has a much bigger prop on the same engine and transmission combo.

Still, based on my performance, I wonder what props you guys have to get six knots out of the boat.
 
B

Brad on Vashon

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Jan 27, 2012
65
Catalina 30 Vashon
I have been reading up on other posts about props and boat speed and have come on a couple threads about the extendo prop. The short story is that it has an elongated hub which allows yu to get a 15" prop. Apparently the larger prop is ideal for a diesel and it's better low end torque.

Thoughts?
 
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Inter20sailor

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Sep 18, 2009
58
Beneteau Oceanis 38 Long Beach
80%
That is the magic number for a diesel engine. When I first took our boat out, I ran the engine to redline a few times (just for a second or so) to determine what the redline really is. After a few times of doing this, and getting consistent readings, I took 80% of that number.

Diesels like to be run, and not lagged. Also, you will here a 'sweet spot' that should be close to that 80% number.

IMHO, I don't think you will do damage by running at 80%rpm.
Cheers,
 
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