Whaler Drive v. Notched Transom

[wallymotor]

Does anybody have side-by-side performance numbers on the same Boston Whaler boat hull and motor for a notched transom boat and a Whaler Drive boat?

I am looking at a Revenge 25 W-T with a Whaler Drive. I noticed in the Revenge 25 hull specifications in "Reference" that the standard notched transom hull has a 300-HP rating while the Whaler Drive version has a 450-HP rating. The only differences in specs with the Whaler Drive is 2-feet more length (8%) and 250-lbs (6%) more weight, yet the horsepower rating is 30% more!

If I buy this boat and re-power with a 300-HP four-cycle engine, will the performance match the standard notched transom hull? To get to the maximum rating for the Whaler Drive I'd have to get twin 225-HP engines, which would be way more weight, cash, and fuel costs than a single 300-HP.

So does the Whaler Drive hull REQUIRE more horsepower or does it simply ALLOW for more horsepower?

I've read many of the old threads on Revenge's with Whaler Drives. The only thing that come close to a comparison are "jimh's" observations from a 2008 thread which states

...Boston Whaler boats with a Whaler Drive are not as common as boats with a notched transom. The Whaler Drive option was expensive. Having had a REVENGE 22 Walk-Through with Whaler Drive for several years now, I can tell you that I really appreciate the Whaler Drive for:

--adding a nice closed transom to the boat
--creating closed storage space in the stern of the boat
--significantly improving the ride characteristics
--creating a nice swim platform

The downside to a Whaler Drive is that the hull seems to need more power to maintain speed. This seems to result in lower fuel economy.

However I also found an article on continuouswave (in "reference" I think) on Engine Brackets which seems to say the opposite :

It is often desirable to move the mounting point of outboard engines aft from the hull's original transom by as much as 36 inches. The two principal benefits of this are:

•The propeller runs in cleaner (i.e., less-turbulent or less aerated) water that exists behind the boat.
•The engine can be raised (sometimes several inches) which reduces the hydrodynamic drag by having less of the engine lower unit submerged in the water.

The net effect of these changes is to increase the propeller efficiency (from operating in cleaner water) and to decrease drag (from reduction of submerged lower unit). This increases the potential top speed of the boat, and improves the overall fuel economy.

If anyone can share their realworld experiences I would appreciate it. I can't go more than 300HP and I don't want to underpower the hull.

The only hard numbers I could find are in a thread from 2010. Here are "crow's" numbers from a 1985 Outrage 25 re-powered with a Suzuki 300.

Code: Select all

RPM       MPG       MPH
2500      2.99      12.99
2800      3.43      15.43
3000      3.72      21.23
3500      3.64      25.06
4000      3.59      33.52
4400      3.00      35.15
4500      3.00      37.75
5000      2.49      42.34
5500      2.14      47.10
5900      2.09      50.46

I would be very happy to get close to these numbers with a 25 Revenge W-T Whaler Drive hull.

[macfam]

Wow, those are impressive numbers!

Our 1988 Revenge W-T with notched transom, and 250 Yamaha OX66 would do 42 to 43-MPH--that's it.

I think the single 300-HP with the Whaler Drive would do better than the 250-HP notched transom and reach over 45-MPH--Not bad!

I think the higher rating for the Whaler Drive is "allowing" higher horsepower more than "requiring" it. Do the specs list the minimal horsepower for both hull forms?

[Hoosier]

This is an interesting question. The only times that I know about when the same hull was run side by side with and without the Whaler Drive, are when Manic Moment, my 1992 23 Walkaround with a notched transom, and Holly Marie, a 23 Walkaround with Whaler Drive, were together on two summer cruises. We didn't have any drag races and the HP of the boats was very different. Mine has twin Yamaha F150 four-cycle engines and John's has twin Yamaha 225 two-cycle engines (I think). As far as I could tell we had comparable performance but Holly Marie seemed to do better in a seaway.

[jimh]

A boat with a Whaler Drive compared to the same hull without the Whaler Drive will run slower with the same horsepower. That's because the Whaler Drive boat is a longer and larger boat.

A Whaler Drive is unlike a pure engine setback bracket because the Whaler Drive will still be running with most of its bottom surface in the water when the boat is on plane. A boat with a pure engine setback bracket will typically run with the bracket completely out of the water when on plane.

If you measure the "performance" just on the basis of the maximum speed possible with a given horsepower, the boat without the Whaler Drive will be faster. But maximum speed is not the only measure of performance. The Whaler Drive boat will handle much better, in my opinion, than a boat with the same hull and without the Whaler Drive. The ride characteristics will be different. The Whaler Drive boat will:

--have less bow rise transitioning to plane; the Whaler Drive tends to limit the bow rise to a very few degrees

--ride more smoothly in waves; the Whaler Drive boat rides like a boat that is two-feet longer, thus has a bigger boat's ride

To use performance data for an OUTRAGE boat to predict performance for a REVENGE model on the same hull will lead to disappointment; the OUTRAGE boats will always be faster than the REVENGE because they weigh less and have no superstructure to create drag. I would not anticipate that a REVENGE 25 notched-transom boat with a 300-HP engine would hit 50-MPH.

[jimh]

Re DAVID's comments about the 23 WALKAROUND boats with and without Whaler Drive:

The Whaler Drive used on the 23 WALKAROUND is not the same design as the Whaler Drive on a REVENGE 25. The name is the same but the design is different. The 23 WALKAROUND Whaler Drive will run with most of the Whaler Drive out of the water when the boat is on plane.

[jimh]

The Whaler Drive boat has several desirable attributes, not directly related to top speed performance:

--closed transom; this keeps the boat completely dry in any sort of following sea conditions, no water sloshing around the engine splash well or coming over the splash well dam into the cockpit

--closed storage area in the stern; a lot of gear can be stowed in the enclosed area of the Whaler Drive; typically the boat's batteries and electrical switches are under the aft deck of the Whaler Drive boat and out of the weather; all the engine wiring, steering hoses, and other rigging is concealed, creating a much cleaner appearance;

--great swim platform; easier to get into and out of the water for swimming, but you still need a ladder

--the teak hatches; the wooden hatches give the boat a very classic and nautical appearance

--the ride; did I mention the ride?

If you are looking for a cabin boat, a REVENGE 25 W-T Whaler Drive is a fantastic boat. The cockpit is huge. The cabin is quite delightful for overnight sleeping.

[cc378]

I have had two boats with WhalerDrives. And I love them!

For the past six years I have run an Outrage 20 WD with a Honda 200. It is a fantastic boat and performs great. Top speed 40ish and the closed transom makes it feel like a bigger boat as compared to my friend's Outrage 20 notched transom. (By the way the boat will be for sale in Spring.)

I just boat a 1990 Outrage 25 WD. After much research with very informed people and balancing many factors, I am replacing the twin 1990 Yamamah 200s with twin Honda 150's. The weight will be similar and since my WhalerDrive is setup for Twins, I stayed with twins. I went Honda because of my mechanic... I am convinced the boat will have plenty of power.

I can report more in the spring after the repower.

Stephen

[wallymotor]

Hey all thanks so much for the feedback. A lot of positives for the Whaler Drive.

macfam: great idea. I checked the minimum HP for both boats and it is the same--115HP. I think you are right: the Whaler Drive is allowing higher horsepower more than requiring it.

To me it sounds like the benefits (as per jimh) of the Whaler Drive--" less bow rise transitioning to plane; the Whaler Drive tends to limit the bow rise to a very few degrees" and "ride more smoothly in waves; the Whaler Drive boat rides like a boat that is two-feet longer, thus has a bigger boat's ride"--outweigh the loss of top end speed.

It makes sense that an Outrage 25 powered by 300-HP will be faster the a Revenge 25 powered the same motor by because of less weight and windage. However those OUTRAGE 25 numbers are all I could find. I agree with macfam: I think a Revenge 25 W-T with Whaler Drive and a single 300-HP outboard might do 45-MPH WOT.

Anyone else care to extrapolate or guess based on the Outrage numbers?

[jimh]

Here is my estimate for the performance of a Boston Whaler REVENGE 25 W-T Whaler Drive and how I arrived at it:

On my REVENGE 22 W-T Whaler Drive boat with 225-HP, top speed is around 44-MPH, depending on conditions, weather, load, and all the usual factors affecting performance. The hull weight is said to be 2,600-lbs. My experience is the rest of the gear usually found on the boat will add at least 2,000-lbs. So we have an underway weight of 4,600-lbs. This gives us a Weight-to-HP ratio of 4600:225 = 20.44-lbs/HP.

A REVENGE 25 W-T Whaler Drive boat has a hull weight of 4,250-lbs. If we assume that the engines and gear and other added weight will be about the same as on my boat, we'd have an underway weight of 6,250-lbs. That gives a Weight-to-HP radio of 6250:300 = 20.88-lbs/HP.

The weight-per-HP loading is very similar on both boats. The hulls are very similar. Because boat speed is always a function of the ratio of weight and power, based on the similar hulls and similar weight-to-power ratios, I would expect that a Boston Whaler REVENGE 25 W-T Whaler Drive with a 300-HP engine would have just about the same performance as my boat, that is, it would hit about 44-MPH as a top speed.

Other factors that might affect the performance:

--the deadrise of the 25-foot hull is greater than the 22-foot hull, so it might require a bit more horsepower to propel at a particular speed

--the beam of the 25-foot hull is wider than the 22-foot hull, so it might require a bit less horsepower to propel to a particular sped.

These two factors might compensate for each other and produce a zero net effect.

In any case, I don't think you will have a 50-MPH boat with a Boston Whaler REVENGE 25 W-T Whaler Drive with a single 300-HP engine. If your proper enjoyment of boating requires that your boat be able to reach 50-MPH, you need to look for another solution. By the way, Boston Whaler boats at 50-MPH are usually not very fun boats. The hulls were not really intended for that sort of speed. You can push them to that speed, but I don't think you will want to run all day at that speed with them. They are much more comfortable making about 27 to 32-MPH. A Boston Whaler REVENGE 25 W-T Whaler Drive will run beautifully in that speed range and give you a marvelous ride.

[msirof2001]

One negative of a Whaler Drive for fishermen who fish while anchored: the wind makes it such that you fish on the stern and the Whaler Drive with engines becomes a huge physical obstacle. Also, for fishermen fishing while not anchored, the boat drifts engines into the wind. And the Whaler drive creates a huge obstacle. Fighting a tuna around a Whaler drive is much more difficult than with a notched transom.

[crabby]

I have a 1990 Outrage 22 Whaler Drive that used to be a OUTRAGE 22 CUDDY Whaler Drive. I replaced the twin Johnson 150-HP engines that were mounted on it when I bought it with an E-TEC 250-HP.

I removed the Cuddy as it became clear to me that it was pretty useless for my needs and killed my fishing space. Before I removed the cuddy I could hit 47-MPH.

My top speed with the 250-HP is about 46-MPH right now WITHOUT the cuddy cabin. What is even more odd is that since removing the cuddy I stripped the bottom paint completely and added three coats of barrier paint (in addition to bottom paint); the old bottom paint was about ten layers thick, chipped, peeling, and rough as could be compared to the way the bottom is now. As a data point, the boat does not a have a T-top or any canvas rigged (yet), and swings a REBEL 15-pitch propeller to a little over 5,700-RPM. The running load is usually myself (200-lbs) and dog (115-lbs) and 20 to 30-gallons of fuel.

[jimh]

The report of the OUTRAGE 22 Whaler Drive hitting 46-MPH with a 250-HP engine is well correlated with my report of my REVENGE 22 Whaler Drive hitting 44-MPH with a 225-HP engine.