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Author Topic: Cruising Speed/RPMs with Universal 25XP  (Read 799 times)

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sailscituate

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Cruising Speed/RPMs with Universal 25XP
« on: August 03, 2019, 06:47:40 AM »

Looking for some insight/guidance on what we can expect under motor (acknowledging the variability of conditions). Generally speaking, we don't do a lot of motoring. We're on our first extended cruise and have run into unfavorable winds. I have a two-blade prop (not sure of the pitch) and have been maxing out at 4-4.3 knots. RPMs are at 2500, temperature a steady 160. We've got a long slog tomorrow with 8-10 mph winds forecast to be on the nose. Wondering if I just need to accept the fact that this is about as good as I'm going to get from the 25XP with my current prop configuration. Would also welcome thoughts on what I could expect by investing in a new prop.
Thanks in advance.
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Ken Juul

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Re: Cruising Speed/RPMs with Universal 25XP
« Reply #1 on: August 03, 2019, 07:35:56 AM »

M25xp with a 3 blade Michigan Sailor 5.5-6 depending on how heavy we are and wave conditions.
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mark_53

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Re: Cruising Speed/RPMs with Universal 25XP
« Reply #2 on: August 03, 2019, 08:55:51 AM »

M25XP 6.5 -7knots with a 3 blade 10 pitch prop. in protected water with no wind at 2500rpm.
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1989 C34 Mk1 M25XP

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Stu Jackson

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Re: Cruising Speed/RPMs with Universal 25XP
« Reply #3 on: August 03, 2019, 11:08:05 AM »

M25 6.5 -7 knots with a 3 blade 15 x 10 pitch prop. in flat water with no/little wind at 2800rpm, clean bottom, 2500 rpm is 6+ knots.  WOT that I check regularly both in gear and out of gear is 3000.

My PO removed the two blade, so I don't know what that performance was nor do I recall the dia / pitch - it's somewhere at the bottom of my locker.
« Last Edit: August 03, 2019, 11:09:08 AM by Stu Jackson »
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Stu Jackson, C34 IA Secretary, #224 1986, "Aquavite"  Cowichan Bay, BC  Maple Bay Marina  SR/FK, M25, Rocna 10 (22#) (NZ model)

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Ron Hill

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Re: Cruising Speed/RPMs with Universal 25XP
« Reply #4 on: August 03, 2019, 12:43:16 PM »

As I recall the factory spec. 2 bladed prop is a 15" X 10". 
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sailscituate

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Re: Cruising Speed/RPMs with Universal 25XP
« Reply #5 on: August 03, 2019, 01:39:15 PM »

Thanks for the input. Obviously I'll be shopping for a 3 blade this winter. For the short term, any thoughts on running at 2800? I've pushed it on a few occasions, but haven't run that high for any significant time.
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KWKloeber

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Re: Cruising Speed/RPMs with Universal 25XP
« Reply #6 on: August 03, 2019, 01:59:06 PM »

Two questions - is your rpm accurate? Is your speed over ground accurate?
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Twenty years from now you'll be more disappointed by the things you didn't do, than by the ones you did.
So throw off the bowlines.  Sail away from the safe harbor.  Catch the tradewinds in your sails.
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sailscituate

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Re: Cruising Speed/RPMs with Universal 25XP
« Reply #7 on: August 03, 2019, 05:30:55 PM »

Yes on both fronts.
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Noah

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Re: Cruising Speed/RPMs with Universal 25XP
« Reply #8 on: August 03, 2019, 05:46:37 PM »

M25 6.5 -7 knots in flat water....with no/little wind at 2800rpm, clean bottom, 2500 rpm is 6+ knots.  WOT that I check regularly both in gear and out of gear is 3000.
I get approx same speed as Stu, on my 25XP but I have a 3-blade Flexofold—which I “hope” gives me more speed under sail than a fixed-bladed prop.
« Last Edit: August 03, 2019, 05:48:25 PM by Noah »
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KWKloeber

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Re: Cruising Speed/RPMs with Universal 25XP
« Reply #9 on: August 03, 2019, 05:53:43 PM »

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Twenty years from now you'll be more disappointed by the things you didn't do, than by the ones you did.
So throw off the bowlines.  Sail away from the safe harbor.  Catch the tradewinds in your sails.
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Noah

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Re: Cruising Speed/RPMs with Universal 25XP
« Reply #10 on: August 03, 2019, 05:56:15 PM »

Less drag.
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Stu Jackson

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Re: Cruising Speed/RPMs with Universal 25XP
« Reply #11 on: August 03, 2019, 08:06:18 PM »

Thanks for the input. Obviously I'll be shopping for a 3 blade this winter. For the short term, any thoughts on running at 2800? I've pushed it on a few occasions, but haven't run that high for any significant time.

I ran at 2800 from SF to Maple Bay, British Columbia, in 2016, 1500 nm, 7.7 knots.  Don't "baby" the engine.  Still runnin'.  :D

I put a 3 inch HX on eons ago.

180F
« Last Edit: August 04, 2019, 09:11:09 AM by Stu Jackson »
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Stu Jackson, C34 IA Secretary, #224 1986, "Aquavite"  Cowichan Bay, BC  Maple Bay Marina  SR/FK, M25, Rocna 10 (22#) (NZ model)

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Phil Spicer

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Re: Cruising Speed/RPMs with Universal 25XP
« Reply #12 on: August 04, 2019, 08:56:06 AM »

   All of our racers down play the 3 bladed prop because of the drag, but it will back down right now. Wife does all of the motoring in and out of the dock. Some times I get a little worried if she comes in a little hot, but in 25 years she has always stopped well short of that steel sea wall. Fixed or folding, your choice. To me, I'll stay with 3 blades. (i don't race)
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britinusa

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Re: Cruising Speed/RPMs with Universal 25XP
« Reply #13 on: August 04, 2019, 09:10:10 AM »

Hey Guys,
would you go back and edit your posts in this thread and include the following:

Boat Name
#of Prop Blades
Max Engine RPM
Typical Temp at Max Engine RPM
Avg Speed at Max Engine RPM through the water.

I'm compiling a spreadsheet with averages that might help everyone.

Thanks.

Eximius:
3Blades
2100 RPM
152ºF (148ºF Thermostat)
6.5knots

Thanks.

Paul
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Paul & Peggy
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Ron Hill

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Re: Cruising Speed/RPMs with Universal 25XP
« Reply #14 on: August 04, 2019, 12:37:36 PM »

Guys : A while back I wrote a Mainsheet C34 Tech Note article on "Boat Speed; Prop and Engine"!!  You might find it interesting reading!!

A thought
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