Very Hypothetical Question Re: CD 25

A

Alexander

New member
IF someone wanted to use a CD 25 like an Albin 25 or 27 as a 25' Trawler speed cruiser , how would you power it. What hp do you think it takes to cruise at 6-8 kts (displacement speeds) with a top speed of 10-12 or something but maximum economy at 6-8 kt cruise.
I'm thinking it might be something like 15 - 30 hp. Maybe twin 9.9 Hondas.
Let me clarify, I am not doing this but am having a theoretical discussion with a friend who is contemplating buying an Albin 25 thinking it is the ultimate small cruiser. I think the advantages of the economical 4 cycle outboard as well as the ability to tip them up out of the water etc make something like a CD 25 or 22 a viable competitor for the best small trawler title.
 
Having looked at, and talked to owners with the 50 hp single on a 22--that is about where you would be for a 22. I have never seen the HP that low on a 25--but I would probably need at least 90 to get the Max 10 to 12 knots.. (and you would really be working that engine hard). A lot would depend on boat loading (weight). q 50 on 25 would keep you below the 10 knot speed, most likely. The weak 130 (closer to the 115) struggles on the 25 to get good planing speeds with a load for a month cruise. It would do OK for a light boat. (from personal experience)

The more economical speed is not going to be 6 to 8 knots--in fact that will not be a very economical speed at all. Lets say that the LWL of the 25 is 22 feet, Sq root 22 is 4.69, x 1.34 = 6.2 knots--and that is going to be about the maximum displacement speed, that will be at all effecient--from that speed on up, you are in the semi displacement range. The displacement range is going to be less than 6.2 knots--and probably the best compromise between speed and mileage is going to be less than 5 knots. Boat Test only did 3.1 knots (5.4 miles'/gallone) and 5.1 knots at 5.7 miles per gallon. Their next test point was 6.5 knots and 5.4 miles per gallon. at 7.5 knots the mileage was down to 4 mpg, and at 8.7 knots was 3 mpg. The next 500 RPM jump took the boat to 13.4 knots (planing) and 3.4 miles per gallon. (Or less than a displacement speed of 8.7 knots.

Consider that the Albin 25/ 27 is a semi displacement, more round bulge boat--so the dynamics are slightly different. Also these boats are driven by a low Hp diesel. When these were repowered--as many have been--The HP was bumped up to as much as 150 HP. The original 25's got 5 to 6 miles per gallon--and low speeds. Diesel is about 20% more efficient that a gas engine.
 
I'd still power it with roughly a 150hp outboard. If you stay at 6-8kts you'll still get great fuel economy and you'll have a boat that can run 25kts when conditions permit or when desired. You can, of course get 6-7 kt cruise with much less horsepower and I bet 9hp would be plenty for that. As Bob mentions above, you'd need a lot more to get to the 10-12kt range. However, unless one was really focussed on long range performance, exceedingly light-weight and low up-front costs, AND you weren't planning on selling any I can't see a strong argument for the lower power.
 
Again, I have a lot of experience in a 26 foot sailboat which was arc bottom, very; similar to a C Dory25 . Initially we had an older 5 HP and the boat would run 4 to 5 knots. Later we put on a 9 HP, and it was no faster. The larger prop of the older 5 was more efficient. Had a Catalina 27, with a 15 mph--and again--6 knots was about it--and the Cat 27 probably was an easier driven hull than the C Dory 25, at those low speeds. A Big foot, or high thrust 8 hp outboard would be the best of that type, but you are looking at about 6 knots max realistic cruising speed--and probably better at 5 knots.
 
I always liked the aft cabin set up of the Albins. I was looking at the 27 AC before my wife hit on C-Dory. A 27 AC with a camper top between the forward and aft cabins would give you a lot of space.

While the Albin is nice, one of the big advantages of the C-Dory is the ability to get up and go if you want/need to. The normal max speed of the Albins is about 6-7 knots. On the 27 if you get the big engine you can go about 10-11 knots.

Having a C-dory that is limited to about 6 knots because of the engine size seems counter productive. I would think that a single ~50 hp would be a better choice. You could cruise at trawler speeds if you want but still have a bit of power to go faster if you really need/want to. You might be able to get a 25 up to about 14-15 mph with a 50 (but I'm guessing).

The other issue with the Ablins is that they haven't been made since the late 70's, early 80's, so you are going to get a fairly old boat if you can find one. But they can be a lot less expensive to buy than a C-Dory (a couple of years ago a nice 27 could be had for around $20-25K, sometimes less).

If you are only going to go slow anyway, the Albin might give a better ride. It is heavier and has more of a displacement hull. Might be less "corky" than a C-Dory.

In theory, the 27 is trailerable (if you can find a trailer for it) but it is not used that way very much at all. The 25 is more trailerable, but I don't think it is as easy to get around as a CD25. This is another reason why we went with the C-Dory.
 
We were rafted up with an Albin 25 recently at Lake Pleasant. I noticed that our C-Dory 25 was much more stable than the Albin when we were hit with the wakes of passing boats. The owner of the Albin indicated that his boat liked to roll a lot when traveling in beam seas. He has a sail rig which is used primarily to stop the rolling when underway, but he has yet taken the time to rig the sail as he trailers the boat often.

The Albin has a nice swim platform which makes it easy to carry a hard dinghy, but you have to crawl over the rear cabin to get to the swim platform.

The Albin boat is interesting and has some nice features, but I think our C-Dorys are a better compromise.

Tony
2006 C-Dory 25. C-VIEW II
 
I've admired the Albin 25 for years, and it came down to an Albin 25 or a C-Dory 22 when I was shopping. I think I could have been happy with either, but what swayed me toward the 22 were three main things:

1) Lighter towing weight (staying under or around 5,000# opens up a lot of vehicle options)

2) Bigger selection of boats in better condition.

3) Not standing right on top of an engine when underway (I like it to be as quiet as possible).

I have seen one Albin 25 that was re-powered with twin outboards on a bracket - that could be slick.

At any rate, from what I have read, with 4-stroke outboards you get about the same fuel consumption going 6 knots with a 20 hp engine as you do going 6 knots with an 100hp engine, so it's about how much horsepower you are using at the time. If that is true then the theoretical fuel savings is a non-thing. That would leave a savings in weight and cost (by going with a small engine only), but the bummer of having a planing capable boat that could only go hull speed. Most people's "human nature" would probably find that irritating eventually, but then a boat only has one owner to please.

Seems like 9-18 hp should push most things at hull speed (I have a friend who powered his 20,000# sailboat with a 9.9 high-thrust outboard for many years prior to putting the inboard in - he went down the Mississippi and over to The Bahamas among other things.). Not that I know for sure though!
 
I love hypothetical questions!

A 90hp four stroke will plane a 25 as long as it is not heavily loaded. It struggles to do it and would not be a very good idea for regular high speed use. I would go bigger if that was needed with just maybe a new Yamaha 115 at the very smallest end running a light boat at higher speeds rarely.

Otherwise, I would consider either a "bigfoot" or "high thrust" 40-60hp engine for the performance envelope you are talking about or just save more cash for pure trawler action and use a single 9.9 FI Suzuki or two of them for improved docking maneuverability and redundancy and prop them for the task.

Any of these alternative motors on a 25 would be hard to re-sell of course....unless gas prices go way up.

Greg
 
I'm with RogerBum, big engine, go slow. I think I'd put maximum allowed horsepower on the boat, which I believe is 200 HP. With the windage of a 25, and the flat bottom/shallow draft, I would be very leery of a severely underpowered boat.
 
Sorry for bumping an old thread but I just came across this. It's definitely an interesting question!

I would also be inclined to go with the big 4 stroke and then run her at displacement speeds. I did a few hours of very slow speed cruising in October with my 200hp Suzuki and the motor seemed very content. I did like 6 or 7 knots for a while. It was very calm and relaxing! I felt like a trawler. Lol

NOW, if budget is a factor then I'd be willing to go considerably lower on the OB. I think a 115 would work quite well for slow speed cruising on the 25. I wouldn't wanna go lower than that.....No way.
 
We bought a 22 cruiser with a 50 Honda with 3 big guys on board top speed was 15-16 mph and nice cruise at 5-6 mph We traded up to a 90 hp (2L version) in 2006 suzuki and she then would get up to 35-36 mph way to fast for a 22 cd
I could see a new merc 115 CT (2.1L) on the 25ft cd would probably get up to 23-25 mph plenty of torgue and would sip fuel at 6mph less then 1 gallon for 6 mph
On our Venture 23 (cape cruiser) we have the 115 Ct and I'm getting about 4 mpg cruising 4000rpm 20-21 mph. At 4500rpm 25-26 mph 5400rpm 30-32 mph Great motor so far have 45hours on it and 7 months young The fuel economy goes down with the higher speeds about 3 mpg anything over 4500rpm
 
First of all, there is no such thing as a perfect set up between boat and
power source. There is always some compromise in either fuel economy
or performance.

Under power the thing and the small engine(s) has to work hard to do
more than displacement speed and there's not much reserve HP to
outrun something you don't like - bad weather, bad people, bad
scheduling, missing the bar scene, etc.

Over power the thing and run the engine for long periods at fewer rpm
than the Mfg recommends and you'll have unwanted engine repairs, maybe
from not getting up to the recommended operating temperature.

Your best bet, unless you're an expert, is to go with what the pros have
already R&D'd: a tried and true brand name vessel which best suits your
intended purpose. Trying to 'do one better' usually ends up afloat with regrets.
An exception may be one who loves to 'tinker' and continually make
'improvements' which later will be improved.

Aye.
 
Not entirely sure why this old thread came up again, but the original C Dory 25 "Cruise ships" were powered with 90 HP Honda (~1.5L). The hull is the same as current C Dory 25, but different cabin layout--and maybe a few more lbs weight??.
I believe that all 6 of these were repowered before the 90 hp failed; most to the 150 Honda. They just did not perform above 11- 12 knots and the owners didn't find this satisfactory. When you are not on a planing stage, and pushing water, the fuel economy will be poor.

My 25 had the Honda 130 (same block as Honda 115), which was a ~ 2.25 liter engine, and although it was marginally OK when light at sea level; when loaded for cruising 17 mph was about the highest reasonable speed one could achieve. One had to severely drop the pitch if the boat was at Lake Powell to get reasonable performance. Based on my experience, I doubt that the smaller displacement 115 HP Merc would do any better than the 130 HP honda.

I believe that it would be a mistake to power a 25 with anything less than 150 hp.

As to Foggy's statements: For a very large number of outboard powered planing small boats, there is certainly a consensus of the min and max hp for each of these boats, and it is a fairly narrow range.

Over power the thing and run the engine for long periods at fewer rpm
than the Mfg recommends and you'll have unwanted engine repairs, maybe
from not getting up to the recommended operating temperature.
Click to expand...

Certainly we all agree that getting the engine up to operating temp is important, but, at least in our waters, that is easily achieved at a high idle. I don't recollect seeing documented "fewer RPM than the mfg. recommends" on outboards. The modern 4 stroke outboards which get the 5000 to 9000 hours time before failure are engines which are run daily, and a fair part of that time is a idle or low speeds--as used by harbor patrols, Coast Guard, and charter fishermen (trolling). For diesels there are recommended run specifications as to min. RPM, as well as Max RPM. I have run both NA and Turbo diesels at lower than those RPM's for thousands of hours with no ill effects (but the engine was up to op temp, and I did occasionally run the RPM to max rated to be sure that there was no evidence of carbon build up.

Of course you could put one of the "big foot" 8 to 15 hp and live with 5 to 6 mph, or just use the kicker for this, and still have the 150 for times you want to go fast!
 
Hypothetically, I'd just power the boat normally. One could efficiently run at those speeds using one of a pair of twins, or with a large 150hp main, or with a 9.9 kicker. I think in this setup I might go slow with a kicker and keep the main for limited use.

If I were planning to run like this often, I'd probably go for a little larger engine, like a 15 or 20hp, and make sure to have it rigged for controls, with an alternator and a high thrust lower unit/gearbox.

Then you get to do most of your maintenance on a less expensive platform!

I actually use my kicker quite a bit for slo cruising. I use less fuel than running slow with my 90, and it's quieter. I usually do it for the cockpit steerin (mine's a tiller), but still, I like it.
 
The original question was ---"IF someone wanted to use a CD 25 like an Albin 25 or 27 as a 25' Trawler speed cruiser , how would you power it?"

So in the spirit of the original question, let's imagine that you have purchased a CD25, old or new, with no motor. Now, IF you are only going to use it at "trawler speed", would you really spend the money on a 150HP? Hard to justify spending ten grand more than you have to just for resale, no?

So in that light, how would you power your little trawler?
 
Bill,
You are correct about the original question (2014). Most all of the answers have addressed this. Probably one of the most valid, is that since most people would re-power with a 150 (as has happened with all of the original 25's in the 1996 to 1998 era), there would be more than a $10.000 hit on the resale value. Same has been pretty much true of the 22's sold with 50's--most have re powered with 90's
The original question also involved the advantages of an outboard powered C Dory 25 over the inboard diesel Albin.

Powering only with a 9 hp kicker, means that in some wind / wave conditions you might not be able to make your port if it is to weather. A lot of the issue with the smaller engines, is that they swing smaller diameter props--thus the reason for "Big foot". I haven't gone thru all of the options--but best would be lower gear ratio, plus more blade surface area.
 
Yeah Bob I just thought that everyone was getting all practical on what was more of a theoretical question. Although if I WAS going to do such a thing, I would still save my money on the front end and let the next buyer buy what they wanted.
But since you can hit hull speed with probably six HP or less, what other considerations would come into play? Perhaps considerations such as fuel economy, engine life, and engine noise? Would not a larger motor running slower be quieter than a small one full tilt? I did think that the dual 9.9s was a cool idea!
 
BillE":3muemuch said:
The original question was ---"IF someone wanted to use a CD 25 like an Albin 25 or 27 as a 25' Trawler speed cruiser , how would you power it?"

So in the spirit of the original question, let's imagine that you have purchased a CD25, old or new, with no motor. Now, IF you are only going to use it at "trawler speed", would you really spend the money on a 150HP? Hard to justify spending ten grand more than you have to just for resale, no?

So in that light, how would you power your little trawler?
Click to expand...

That was the light that I used to write my response. I would definitely power it conventionally, with the mods I mentioned: slightly beefing up the kicker with a higher hp and definitely using one with an oversized lower unit and prop (often call high thrust), remote control remote steering, alternator, etc.

Now if I were really going to have the main/kicker and use the small engine as my main and the kicker as my most frequent power I might opt to go find an inexpensive used 2 stroke 150hp motor. You'd still take a hit on resale, but not as much, plus you'd save weight. Who really cares if you burn extra gas when you use it if you are only using it as a backup.

Reasons you might want to have a full sized motor on there (aside from resale) as a backup are:

1. outrun nasty weather
2. maintain control in nasty weather
3. get through multiple passes on a voyage/fighting currents
4. get home or to port quickly in case of emergency

As I said, I can cruise at trawler speed in my 22 just fine using my 90hp, and do so from time to time, but I enjoy going slow with my kicker a bit more, and if I had it all set up to run remotely, I'd like it even more.

One thing to maybe mention here is that I also keep a generator on board since I do this with a kicker that has no alternator, however, if you were really using the juice with a lot of fancy GPS, sonar, toaster ovens etc, you would probably want to figure in generator charging in terms of volume and fuel use. My generator can charge my battery much faster than even my BF90, so it's not always on, but I do use it occasionally when kicker cruising.
 
I'm with those who suggest normal power, with the option of powering down to displacement speeds to suit. Anything under 25HP would have trouble making way and maintaining control against wind and strong current or waves of any size. The CD 25 was not designed as a displacement hull, and would not handle with stability (like a sailboat for example) going really slow in heavy weather. You would also be creating a very hard-to-sell white elephant (raise your hand those of you who've never sold a boat you thought would be your "last boat"). As Foggy points out, most of the outliers are not copied for the simple reason that it didn't work out well. If you really want a displacement vessel I would suggest buying one like the Timbercoast 22 currently for sale on Yachtworld. Best keep this discussion theoretical. Cheers, Mike.
 
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