which engine for 280 sundancer

[magster65]

The good news is that no matter which configuration you choose... you'll be happy with it.
I wonder if there's any twin 6.2 / B3's around? That would be fun...

 

[ChiefScientist]

My 2008 has the Seacore 496 with DTS. There are several dual powerplant 280's and several more single 280's at my marina on the Ohio River.

After pulling my boat out this winter after 100 running hours in a trash filled river (folks say it was the worst conditions in 10 years), there no damages to the running gear and prop. I believe this is because the V hull pushes flotsam away from the running gear. This was common on the single 280's.

The dual 280's are entirely different. All of their running gear was damaged. One pier mate of mine had the outdrive ripped off his twin. I believe this is because the V hull pushes flotsam INTO the running gear.

So - all in all - I believe the single is lower cost and overall -more reliable when one consideres unexpected damage.

Thanks

 

[Presentation]

my 2008 has the seacore 496 with dts. There are several dual powerplant 280's and several more single 280's at my marina on the ohio river.

After pulling my boat out this winter after 100 running hours in a trash filled river (folks say it was the worst conditions in 10 years), there no damages to the running gear and prop. I believe this is because the v hull pushes flotsam away from the running gear. This was common on the single 280's.

The dual 280's are entirely different. All of their running gear was damaged. One pier mate of mine had the outdrive ripped off his twin. I believe this is because the v hull pushes flotsam into the running gear.

So - all in all - i believe the single is lower cost and overall -more reliable when one consideres unexpected damage.

Thanks

lmfao!

Lower cost? Sure. More reliable? Whiskey tango foxtrot?

Using your logic, a skydiver would be safer if they only pack one chute so they don’t accidently pull the wrong cord.

Note to self: Do not take advice from chiefscientist.

 

[Tippy Canoe]

I had one episode in pretty rough water where some discarded line from an old lobster pot got wrapped around the prop on my single engine boat. I was only about 50 yards off of a very rocky coast where the waves were crashing. It was in one of the deepest parts of Narragansset Bay off of Jamestown so dropping the anchor might not have done the trick in time. Luckily I was able to very quickly wave down a guy in a center console who towed me to safety. That fall I moved up to my current boat with twin 4.3's and I am more comfortable and the admiral is much calmer in rough water. Hey, stuff can happen on any boat at any time but for me having twin engines in my boating environment is the prudent choice.

KV

 

[ChiefScientist]

Presentation -

lmfao!

Lower cost? Sure. More reliable? Whiskey tango foxtrot?

Using your logic, a skydiver would be safer if they only pack one chute so they don’t accidentally pull the wrong cord.

Note to self: Do not take advice from chiefscientist.

Thanks - Presentation - for your analogy! :smt038 I don't argue on line - especially with folks that don't provide their name and can't be looked up. Pulling the right cord is a training issue and sky diving requires training and certification. . . details, details.

However, I think it is obvious to a casual observer that jumping from an aircraft and boating are different activities with a demonstrably different consequence for equipment failure. They have different training requirements as well. Regardles, my recommendation would definitely be different for sky diving. For sky diving, I would want a reserve 'chute and I bet it would still deploy even if I pulled the reserve rip cord first.

If you are typical (no way to know because you don't provide your identity), you most likely drive a car with one engine but might prefer an aircraft with two power plants. These are two different situations - closer to what we are dealing with here, with different consequences for equipment failure and different training/ratings required.

Thanks -

Brett Bonner, P.E. aka ChiefScientist -

 

[Bridog]

Note to Presentation: jump out of a plane. die in a fire.
or just kill yourself.

Enjoy your brief stay.

 

[Presentation]

.......I don't argue on line - especially with folks that don't provide their name and can't be looked up.....Brett Bonner, P.E. aka ChiefScientist

You are relatively new here so I’ll give you a bit of history.

One member here posted his real name. Because another member here did not agree with him this member sent a threatening letter to his wife at their home. This occurred just a couple of weeks ago. Although the member who sent the letter has been banned from this site, he is already back under another screen name.

Given that, please excuse me for not posting my name at this forum.

Due to the letter to the wife situation, many of the more experienced members no longer post here. From memory, none of them claimed to be a scientist or posted things “hey, I’m a P.E. so the STUPID stuff I post should not be scrutinized” however because I got to know the member who’s wife received the letter personally I knew he actually was a scientist with multiple degrees, had worked for NASA as a rocket scientist, and had other accomplishments as well. I’m not kidding, that is his actual history.

In the past I have met several members from this board and have mailed things and received mail form other members here, not threatening letters to my wife.

If you truly feel having one motor is safer than having two due to your personal experiences and you intend to go to sea further away from shore then you can see (don’t worry, the world is not flat, you will not fall off the edge) then I suggest you continue your education.

You may also want to consult with your insurance provider to see what happens to your coverage if you head to sea beyond 50 miles in a single engine vessel. (note: coverage’s vary, 50 miles is given as a example, range may vary)

Regarding wanting to argue, you said something wrong I called you out about it. I may have phrased things less harsh had you not implied the crap “hey I’m a P.E. and even have the word scientist in my screen name and I am posting my name so I must be correct and you must be wrong."

Look, you may be telling the truth about being a P.E. and you may have a great deal of knowledge in your field.

It’s obvious to me that you have a lot to learn about boating and there is nothing wrong with that. None of us were born with boating knowledge.

If you come here with very limited boating related experience and knowledge and state wrong things then claim they are correct because you are a P.E be ready to take some heat.

 

[ChiefScientist]

ntation - I welcome scrutiny. No problem. Scrutiny and feedback is a gift.

For the benefit of the reader here, I did investigate insurance on twin v. single. Since I was making a new boat purchase and had the choice of numerous boats - that was one of the first areas of research. After I decided on the big single, another dealer offered me a twin for nearly identical money. I then did a one-to-one, boat to boat comparison, 5 year comparison. The insurance rates were higher in all respects for the dual engines verses single in all questioned operating conditions. Another form of insurance, the extended warranty, was significantly higher as well.

That said, the "50 miles off shore" question was not asked. But knowing the fuel consumption, fuel capacity, and seaworthy rating of a 280 Sundancer, I would imagine not many of us would go 50 miles offshore - twin or single.

I do admire twins for some better handling in the wind while maneuvering. Frankly, I’m looking at a bow thruster and/or a thrusters that run off the Kohler genset (yes 240V). I’m investigating them now and looking at marine rated thrusters and controllers in the U.K.

As long as the power needs are met, twins/singles are yet another individual choice as are the consequences of the decision.

But I stick by my statement I have observed more damage on twins vs. singles for the reason(s) stated. The increased damage adversely affects reliability.

The pity here is you feel insecure. For instance, you can't use your name. Your insecurity leads you to create stories about threats, NASA, rocket scientists, parachutes, as well negatively react to others that might otherwise apply rational principles to reliability/security/safety question. You post constantly for validation. You NEED twins, triples, or quads. And when they get damaged, I’m sure you will not even think about this chain. Good luck - and I do sincerely hope you and your boat stay safe.

 

[rabyers1]

Not getting into the who's a better scientist/expert argument as I am very far from either. (A know-it-all? - probably!)

It is obvious that having two engines increases a boat's "limp home ability" by enabling it to continue to be propelled thru the water at some level of performance after one of its engine's fails. However, having those two engines does not enable the boat to be properly operated and normally used until the second engine is put back into service. Therefore, each time you begin a boating session, you can't "rely" on both engines to start and operate normally any more or less than you can "rely" on a single engine to start and operate normally. How many folks would even leave the dock with one of their engine's out? So, neither boat is more inherently reliable than the other.

This idea of debris being either pushed into or out of the path of the drives by the center keel is very interesting. It seems like Brett has observed some real differentiation in the damage experiences between single engine and two engine vessels in his marina. Anyone else here observed this at their marinas?

 

[Henry Boyd]

This idea of debris being either pushed into or out of the path of the drives by the center keel is very interesting. It seems like Brett has observed some real differentiation in the damage experiences between single engine and two engine vessels in his marina. Anyone else here observed this at their marinas?

Speaking as someone with commercial marine engineering experience, Mr. Bonner's assertion would certainly be groundbreaking if it were true. In 30 years of reading SNAME papers and industry publications I can't recall anything that would support it. In any event, I think he misses sight of the obvious; two pieces of hardware below the water line equals twice the risk of hitting something.

Henry

 

[Tonka Boater]

Consider that the original poster hasn't logged in since 9/24/09 -- two days after posting the question. I will assume that answering his question is pointless.

As for the larger question -- Twins vs. Single: It's been said a thousand times -- it's personal preference.
.

 

[ChiefScientist]

Speaking as someone with commercial marine engineering experience, Mr. Bonner's assertion would certainly be groundbreaking if it were true. In 30 years of reading SNAME papers and industry publications I can't recall anything that would support it. In any event, I think he misses sight of the obvious; two pieces of hardware below the water line equals twice the risk of hitting something.

Henry

Henry - I respect your experience. Mine is based on a single season observation - my sample is low. But it is an observation.

Here is an article that supports my observation by experts

http://www.passagemaker.com/Magazin...dArticle/tabid/277/articleID/888/Default.aspx

Furthermore, I do believe that the deeper the V, the higher the speed, the more likely twins will be damaged in a situation that a single may not be damaged in.

 

[hack4alivin]

Henry - I respect your experience. Mine is based on a single season observation - my sample is low. But it is an observation.

Here is an article that supports my observation by experts

http://www.passagemaker.com/Magazin...dArticle/tabid/277/articleID/888/Default.aspx

Furthermore, I do believe that the deeper the V, the higher the speed, the more likely twins will be damaged in a situation that a single may not be damaged in.

Good article, I especially liked the part about “get a thruster…. Or practice”. :thumbsup:

I loved our 280 with the single 496, just felt the need for a bigger boat.

 

[Tonka Boater]

Henry - I respect your experience. Mine is based on a single season observation - my sample is low. But it is an observation.

Here is an article that supports my observation by experts

http://www.passagemaker.com/Magazin...dArticle/tabid/277/articleID/888/Default.aspx

Furthermore, I do believe that the deeper the V, the higher the speed, the more likely twins will be damaged in a situation that a single may not be damaged in.

That is a great article and it brings up a lot of other points that have never been considered in the debates here.

I especially liked this quote: "Get a thruster…or practice." I also agree with the article when they say that docking a single screw is a "thinking mans game". Soooo true. I was terrified of docking my 280 when I first got it. Back it into the slip!?!? Wind? Forget it, I would even go out. With practice and quick thinking....it's no problem now.

Thanks for sharing.
.

 

[Hampton]

Single engine trawlers - de-tuned versions of very power motors operating at the bottom end of their power band - very reliable, very efficient, don't push hard, don't plane, don't break. Today's cruisers - High power versions of normally reliable engines - turbo charged, cruise at 85% max RPM, going to great places at great speeds - not the same.

Airplanes - twins have twice the chance of engine failure (boats too).
How much power does the remaining engine have when a twin loses one? Just enough to get you to the scene of the accident.

Boats - Slow speed cruising, or work boats operating several days per week, or safe, lake boating, or maximum efficiency, get a single.
High speed cruising, off shore activities, treacherous waters - get two.

SciFi Guy - Too small of sample in a very unusual boating scenario - no relevance.

 

[mwph]

Henry, John... For people like me trying to learn these are great posts. Thanks guys
for taking the time.

 

[JimT]

You can't correctly compare the reliabiltiy of the diesel power plants in a commercial trawler with Merc gas engines to reach the conclusion that one gas engine is a reliable as two. Even very well maintained gas engines will fail at a much higher rate than diesels. I mean fail to start when you need them not self destruct. Simply put go fast gas engines are not diesels and two of them make it more likely you get home under your own power than by a tow.

 

[comsnark]

Airplanes - twins have twice the chance of engine failure (boats too).
How much power does the remaining engine have when a twin loses one? Just enough to get you to the scene of the accident.

I have a friend who pilots single engine small planes who says something similar.

To the question of single vs twin engine boats;

1) Owning a twin engined boat, I have NO DOUBT twins cost more. There is no multi-engine discount when getting maintenance done. If one oil change costs $190, then two will cost $380. I have no doubt insurance is higher (although I have no direct evidence); Twin Engine boats *tend* to have a higher insured value. . .and that raises the insurance cost.

2) A twin engined boat running on one engine doesn't run like a single engine boat. With one engine, my boat has real trouble getting on plane. I have taken the engine up to 3800 rpm and not succeeded. Didn't push harder, as I am not going to run my engines at 4000 RPM for 30 minutes if I can avoid it.

The few times I have come home on a single engine. . yes indeed, I came home at hull speed.

3) Twin engines are not 100% reliable. They share the same fuel system. You run out of gas. . both engines die. You foul your fuel tank, both engines die. You run your boat through a pile of sea-grass. . .both engine intakes get clogged. On smaller Sea Ray I/O's. .. there is only ONE power steering pump. If my starboard engine quits. . .the boat is manual steering only.

4) This is very true: With two engines, you are MORE LIKELY to have an equipment failure. And it is true: If ONE engine is down, you are not taking the boat for a spin. Been there, done that. Now, I don't believe the probability of a lost weekend is double, since many mechanical issues are maintenance related, and when an item fails on one engine, you think about what is happening on the other engine.

5) Here is why you have two engines: When one engine dies, you can get home without the tow of shame. More importantly, if an engine dies in a REALLY bad spot. . (which in my case was in the middle of the Barnegate Inlet, complete with rocks, shoals, wind and strong tide), you can simply putter away at hull speed, without the crew getting into a panic.

From my experience, the fact you can usually still get home after an engine failure, without the tow of shame, is well worth the many, real costs, of twin engines.


Note: Just because you have twin engines, doesn't mean you can ALWAYS get home on one engine. I still maintain a SeaTow membership.

 

[Henry Boyd]

This is a response to a PM sent to me by Brett Bonner. I am posting it here because my original post was made in haste, and comes off with a tone of “because I said so”. I apologize for that, I should have explained my position better. What follows is an attempt to do so.

I have quoted the appropriate section from his PM. The balance of his PM contains information on his background and boating experience. Given the recent stupidity that ensued over the publication of personal private information here recently, I will leave to Brett to make public the balance of his message to me if he wishes to, but the contents have nothing to do with the technical aspect of the post.


Brett,

We can go round and round on the 'reliability' discussion and at the end of the day it is a combination of semantics and the specifics of a given situation that makes the difference. I will also point out that while the article you posted is the best argument I have heard yet for diesel in favor of gas, it does not make the case for single gas vs twin gas. Marine diesel engines are built like the old Timex watches that were advertised to “take a lickin and still keep on tickin”. It is an apples and oranges comparison.

In a similar vein of semantics and circumstances is the discussion of whether the twin engine boat has better handling than the single. If you learned (as my brother and I were taught to by our dad) to dock a 36' sailboat while under sail and without an engine, then listening to either side of that discussion can be very entertaining.

As to your point about the vee hull. Your statement suggests to me that you are viewing what is happening under the boat from an intuitive perspective. In your PM you write:

“But there is another factor here. A v hull pushes crap toward the outside precisely where the twins are located. As the water fills back in, flosam has further to go before it hits the engine. And the boat is already gone. It can't be just "double the chance" that the twins had damage and the singles had none.”

Here is the thing. What you are describing is the behavior of a true displacement hull. At planning speed, by definition and fact, the Sea Ray hull has overtaken its bow wave, and as a result, the water flow under the hull is in straight lines. This is further ensured by the use of strakes (the vee shaped ridges in the hull, and the chines, the flat almost horizontal part of the hull where it meets the waterline when stationary. Intended to make the hull stay in a straight line and to keep it from skidding sideways in either turns, cross winds/currents, these features accomplish this task by ensuring the water flow under the hull remains parallel with the keel line by keeping it from moving from the keel to the outer edges. This also increases the water pressure under the hull creating lift and decreases the boat’s time to plane.

At planning speeds the amount of water being physically displaced is quite small, and the attitude of the hull bottom has changed to where the back 2/3 is roughly level (parallel with the water surface). In this configuration, the leading edge of the bow no longer looks like a snowplow. And, it is no longer the deepest part of the vessel’s draft. So submerged objects that are on line with the keel line will not get pushed to the side, but down and into our expensive BIIIs!

J.D. Van Manen and P. Van Oossanen, in Volume II of Principles of Naval Architecture, Chapter V Resistance, write:

“In contrast the planning hull form is configured to develop positive dynamic pressures so that its draft decreases with increasing speed, enabling it to run higher and higher on the wave it is generating, thus avoiding the large drag resistances experienced by displacement hulls run at speed. To attain positive dynamic pressures the planning hull avoids convex curvature of both the buttocks and transverse sections. Whereas, in the displacement hull, all means are taken to reduce flow separation, in a planning boat the straight buttock lines are cut off cleanly by the transom stern so as to induce early flow separation. The transverse section is typically a deadrise section with sharp intersection of the bottom and sides to form a hard chine from which the flow will also separate.”

Thus at any speed, the planning hull is designed to separate the port and starboard streamlines, and prevent them from converging at the stern. Additionally, at any speed the hull form is building positive pressure under the hull. Quite simply. it becomes pretty darned hard for a deflected floating object to be ‘sucked’ back under the hull.

At very low speeds, while the hull is in displacement mode, what you describe possibly could happen with the bow deflecting a submerged object into the path of a twin. It is also possible at low speeds, that submerged objects struck by the bow would return to their original course along the keel. But, at such speeds the risk of damage is also much lower.


Henry

 

[msd58]

I know that this thread has taken some interesting turns but I would like to bring motors in a 280 question. I recently looked at a couple of 2001 280's with the 6.2 320 HP Mercruiser Engine. This was offered in late 2001 after the 7.4 was done away with. Its 10 more HP than the 7.4 and a couple hundred pounds lighter than 7.4 Being that looked at these boats while visiting the upper NY state area no water test was possible. I did get some info from one owner about performance:

"....the answer is that this is the Mercruiser fuel-injected MX 6.2L. It is pretty fuel-efficient. We typically are able to reach WOT 30+ knots and comfortably cruise anywhere from 18-25 knots (usually at the top end of that range). We also routinely waterski or drag other toys behind her."

I don't know how that compared to the 7.4