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Author Topic: why are diesel engines getting bigger on the same boat?  (Read 3215 times)

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Terry Forshier

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why are diesel engines getting bigger on the same boat?
« on: April 09, 2006, 09:22:29 AM »

Why does Catalina keep increasing the HP on the diesel? Was this boat underpowered? It seeems to have gone from a 20 hp to now a 30 something hp, in stages? Is it just that boaters today want to do 7 to 8kts under power to keep up with the 40+ footers?  Terry
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Susan Ray

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Re: why are diesel engines getting bigger on the same boat?
« Reply #1 on: April 09, 2006, 10:20:16 AM »

Terry...Was wondering the same thing myself..isn't there some kind of supposed "hull speed" to exceed? Are sailors out there having  power races? I owned a C30 with a 12 hp Yanmar then a C30 with a 23 hp Universal and never noticed much difference in ability to maneuver out of the channel and go sail... and While we are at it...on another thread here, they are wondering about the 'loud noise at 2400 rpm, only in forward, not reverse'. So where was this sailor going in reverse at 2400 rpm? Why would you go anywhere at 2400 rpm? Are you going that much faster than at 16-1800 on a 25 hp engine?. So many questions....Aloha,Susan
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Aloha, Susan on "Stray" in the Ala Wai Harbor, Honolulu Hawaii

Ron Hill

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Re: why are diesel engines getting bigger on the same boat?
« Reply #2 on: April 09, 2006, 06:12:56 PM »

Terry : Good question.  I've noted over the years that Catalina has traditionally underpowered their sail boats.  As Susan pointed out you can get there with a smaller engine -- in a NO wind condition.  If you ever get into weather you'll really appreciate the higher horse power.
I suspect that $$$ is the culprit and as other manufactures up their HP so did Catalina.   :think
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Ed Shankle

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Re: why are diesel engines getting bigger on the same boat?
« Reply #3 on: April 10, 2006, 12:21:14 PM »

I subscribe to the "originally underpowered" theory. While it's just fine to be able to do 6 knots on flat water in no wind, circumstances aren't always that agreeable. For example, per the Coast Guard,  you must power through the Cape Code Canal. I've gone through the canal, east to west, with a fair current, 2800 rpm's, and been stopped almost dead in my tracks by the southwesterlies that pound up the canal and create some tough waves. That's when I'm wishing I had the 35 hp engine.
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Ed Shankle
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Salem, MA

Stu Jackson

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Re: why are diesel engines getting bigger on the same boat?
« Reply #4 on: April 10, 2006, 12:53:45 PM »

I'm a little confused.  I don't believe that the larger engines turn the propellers any faster than the the older engines, so what's the advantage, since a given prop is turning at a given RPM.  I haven't felt underpowered in 8 years with heavy currents here in San Francisco.  My understanding is that Universal stopped making M25s and Catalina bought what Universal was making.  The current M35s just fit in the available space.  I like being able to get to the sides of my M25.   :D
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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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Earl Miller

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Re: why are diesel engines getting bigger on the same boat?
« Reply #5 on: April 14, 2006, 09:07:17 AM »

In response to Susan's question in reply 1 about  the separate thread and why anyone would go 2400 rpm in reverse .... we were diagnosing a harmonic that seemed to be coming from the stern.  The mechanic wanted to see if it would make the same noise in reverse (it didn't) ... I would not recommend doing 2400 rpm in reverse  unless it was necessary, it was a little tough to control.. 
As far as the difference between 1200 - 1600 rpm and higher speeds ... the boat cruises very nicely at 2500 rpm doing 6 knots.  In my last trip from La Conner WA to Gabriola Island BC it was dead calm for the three days and the extra speed was welcome over the 20 hours of motoring.
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Earl Miller, 1989 #923 "Diamond Girl",  Gabriola Island BC

David Sanner

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Re: why are diesel engines getting bigger on the same boat?
« Reply #6 on: April 14, 2006, 02:05:30 PM »

I have a 23hp M25XP with a three bladed fixed prop.  It moves the boat nicely @6+ knots
at 2400rpm and nearly hull speed at WOT.  I'm sure a wider blade quality folding
prop would perform even better, especially in reverse and into the wind.

I wouldn't say that c34's are obviously underpowered, but there are advantages
with the larger engine though trade off is that they typically use more fuel.

- Light winds, calm water, both work well but smaller engine uses a little less fuel.
- Strong head winds, chop, the larger engine moves the boat better.

I assume the 35hp c34 slows down when motoring into the wind and
a reasonable chop but not as much as the original 21-23hp motors.
(Obviously the larger engine will help with boat speed in a headwind but from
the reports I've read the propeller can make a market difference as well)

If you're looking for that last 1/2 of a knot the larger engine combined
with a high pitched wide bladed prop should get you there but I would
imagine at the cost of burning 50% more fuel per hour.  (Granted 3/4 of
a gal/hour instead of 1/2 gal/hour is worth the extra 1/2 knot for some)




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David Sanner, #611 1988, "Queimada" San Francisco Bay

Ken Heyman

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Re: why are diesel engines getting bigger on the same boat?
« Reply #7 on: April 15, 2006, 01:13:33 PM »

Interesting posts - I have a M25XP  with a three bladed prop and it has been fine in challenging weather. I try to remind myself that I am at the helm of a sailboat and engine horsepower should be a secondary consideration. That said when we are cruising on Lake Michigan it is comforting to know that we can rev up the iron Genoa and get to our anchorage or marina more quickly and comfortably than by sail, if circumstances dictate. We have occasionally been caught in some nasty wind and waves right on the nose and our "smaller power plant" has delivered the goods quite adequately. I guess if I frequently encountered conditions such as Ed described in the Cape Cod Canal, the larger engine would be comforting. Short tacking a 34 foot in a narrow channel with wind and waves isn't my idea of a good time.
Recently I sailed with Stu in SF bay in some fairly nasty conditions (by our Lake Michigan standards) and his M25 did just fine coupled with good seamanship. At times we were beating into big wind, waves and current.

If I were to buy another boat I don't think I would put a premium on the larger engine. Evidently those that buy a new Catalina have no choice.

Ken
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Ken Heyman
1988 c34 #535
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Ron Hill

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Re: why are diesel engines getting bigger on the same boat?
« Reply #8 on: April 15, 2006, 02:02:52 PM »

Guys : The M25 & 25XP are great engines, however if my M25XP fails I doubt if an M25 will replace it!!
In case you're interested both the M25 and M35 engines are the same width, but the M35 is 4.3 inches longer(one more cylinder). 
However, at the same rpm the M35 has more than 15lbs-ft of torque!  That's the POWER you'll notice when going into a heavy sea!!   A few thoughts. 
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Ron Bukowski

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Re: why are diesel engines getting bigger on the same boat?
« Reply #9 on: April 17, 2006, 10:23:16 AM »

On "North Star" the P.O., for some unexplaned reason, repowered with a Yanmar 3gm. That is a great engine. With 27hp it has all that a C34 needs.
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Ron Bukowski
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Ron Hill

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Re: why are diesel engines getting bigger on the same boat?
« Reply #10 on: April 17, 2006, 04:30:23 PM »

Guys : It is not unusual to find a Yanmar is a C34. 
Seems that if the factory was short on Universal's, Catalina would call the "new" owner and ask if it was OK to install a larger HP Yanmar.  This was especially true during the M35A 30hp days when they'd substitute a Yanmar 35HP.    :!:
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Ron, Apache #788
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