posted 09-15-2005 08:49 PM ET (US)            

Just out of curiosity, why not move up to the E-TEC 225 which has the same weight of 524 lbs... ?

200 hp = 427 lbs.

200 HO hp = 524 lbs.

225 hp = 524 lbs.

250 hp = 524 lbs.

All of the above engines have the 25" shaft.
Even the 250 hp weighs the same as the 200 HO and the 225...

posted 09-16-2005 03:01 PM ET (US)            

I'm not sure that Jim Potdevin ever said his Revenge 22 goes 49 mph, but maybe. I do know that Pete Butterfield's Revenge 22 will do 49 mph powered by a mid 1990s Yamaha 225 (carbed) and it does have a RADAR arch.

But I do agree with Larry that a Revenge 22 should do better than 42 mph if the motor puts out 220 hp.

posted 09-16-2005 03:11 PM ET (US)            

...or water.

posted 09-16-2005 03:35 PM ET (US)            

Does the forumula take the above into consideration?

posted 09-16-2005 04:37 PM ET (US)         

I also think he has published some of his very precise data in the performance section here. His Coast Guard experience shows! A search may produce it.

posted 09-16-2005 07:16 PM ET (US)            

There isn't a strong correlation between being an Officer in the Coast Guard and small boat knowledge. Now if Jim Potdevin was a prior enlisted Boatswains Mate then I retact my statement.

posted 09-17-2005 12:13 PM ET (US)            

No problem.

My boat: 1990 Revenge 22 WT with 2003 Merc 225 Optimax plus: 9.9 Yamaha 4S Hi-thrust long shaft kicker, bimini (STORED in the up position), 77 gal fuel, extra equipment (200+ pounds?), bottom paint, Cetacea page 44.

Run either a Mirage Plus 19" or Rev-4 17". If I recall my numbers somewhat clearly (speed via GPS, full fuel, 1 pers, wind/current negligible):

Top speed:
MP19 - 43.0 kts = 49.45 mph
Rev-4 - 42.0 kts = 48.3 mph

Top RPM:
MP19 - 5200-5250
Rev-4 - 5600

Cruise:
MP19 - 29.3 kts = 33.7 mph @ 3750 rpm
Rev-4 - 26.5 kts = 30.5 mph @ 3750

Nautical MPG
29.3 kts = 3.1 nmpg = 3.56 statute mpg = ~9.4 gph
26.5 kts = 3.1 nmpg = " " " " " "

Juneau- Glacier Bay National Park - Hoonah - Juneau:
138 nm and used 46 gallons of fuel = 3.0 nmpg (3.45 smpg).
Boat fully loaded with 30 gallons extra fuel, water, camping gear, junk, 2 adults.
Wind 1-5 kts, seas 0-2'.
Mirage Plus 19" cruising at 3900 rpm, 30 kts.

As for being a prior boatswains mate... yes, my parents were married and well I'm a retired buoy tender sailor (blackboats are workboats!), retired in 2000 as an O5, Chief of the Aids to Navigation branch in the 17th CG District. Two afloat commands, 4 afloat tours, 2 rescue centers, several staff wienie jobs. Prior to that first command in 1960 - 9' dinghy with 3 hp. First Whaler 1966 w/ 33 Johnson. Also taught 5 days cruising/sailing course on 26'-41' sloops, yawls, cutters. 92' square topsail schooner New England to Bermuda 5 times as 1st & 2nd Mate. 200 ton CG Masters license. I can report what I see.

nytugcapt - I'd go for a 225 as the Revenge 22 WT can use some extra weight in the stern and the 225 will help resale.

posted 09-17-2005 12:48 PM ET (US)            

Larry I think your post elicited Phatwhaler's comment because your post seem to imply that unless a poster has a Coast Guard affiliation, that poster's performance reports have no credibility here. So apparently performance reports from individuals with 35 years of experience with outboard motors, 30 years of experience with outboard motors and Whalers and 10 years of experience with outboard motors, Whalers and GPS units, as well as 30 years of sailing experience (both cruising and racing) in boats ranging from 8 foot dingys to 30+ foot sloops, but no Coast Guard affiliation, should all now be considered unreliable. Very interesting.

So whether the readers here wish to believe it or not, this performance reporter, with admittedly no Coast Guard experience or affiliation, has experienced stock configuration performance consistent with expectations produced by the speed prediction formula.

posted 09-17-2005 03:44 PM ET (US)            

Congrats. She'll run great!.

posted 09-17-2005 08:51 PM ET (US)            

My comment was made for two reasons.

1. I couldn’t resist an opportunity to elbow an officer in the ribs.
2. Most CG officers don't have a lot of small boat experience. Mr. Potdevin is somewhat of an anomaly.

Hand salute.

posted 09-17-2005 09:56 PM ET (US)            

Salute returned. Got to try some of your cocktail cruising.

posted 09-18-2005 11:19 AM ET (US)            

I was looking at JimH's propeller test reports (see continuouswave.com/whaler/reference/propellerWDSingle.html and it appears to me that JimH's 22 Revenge WD falls into the same category as all of mine have -- a Whaler that has a hull factor in the 180 neighborhood and this is without bottom paint. According to his report, the speed prediction formula using a hull factor of 180 predicts 39 MPH for his estimated 4800 lbs of weight and his actual reported speed was approximately 40 MPH depending on the propeller. His experience is the same as mine, essentially within the +/- 1 MPH of predicted speed. My guess is that without bottom paint, his hull factor is slightly higher than 180.

Now, based on JimP's report, I estimate his total weight (boat+motors+gear+person) to have been 3,850 lbs (2350 lbs for the boat, 620 lbs for the motors, 200 lbs of gear, 175 lbs of persons, 508 lbs of fuel). Using the speed prediction formula with 225 HP and the 180 hull factor, top speed should be 43.4 MPH, 6 MPH less.

Now, according to the speed prediction formula, in order to achieve 49.5 MPH with this total weight we need to have either 290 HP on the transom or a hull factor of about 205 assuming that the Mercury Optimax 225 only produces 225 HP. Now we know from LHG that Mercury motors are in another league, perhaps other-worldly at times, but 290 HP from a 225 even is unlikely. From my results on a variety of classic Whaler hulls with more or less factory recommended rigging and from what I've read about JimH's experience, I don't believe a hull factor of 205 applies to the Revenge as that number exceeds the 17 Montauk's higher hull factor of 200. So how do we explain the differences between predicted speed and actual speed?

If we assume that the Mercury Optimax 225 produces 247 HP (110 percent of its rated HP, the ICOMIA limit) in Alaskan weather conditions and we use the 180 hull factor, predicted top speed is 45.5 MPH with the estimated weight. That doesn't get us there. To achieve 49.5 MPH with 247 HP, we still need a hull factor greater than 195, which puts us in the classic 17 Montauk territory.

If 180 is the correct hull factor, then another explanation could be weight. More specifically, using 247 HP on the transom and a hull factor of 180, the weight of JimP's Revenge would have to be 500 lbs less than my estimate, essentially the difference between a full tank of fuel and a nearly empty tank.

In any event, this whole discussion started with a challenge to what is perceived to be a low predicted top speed. If for some reason the NYTugCapt's 22 Revenge with his new E-TEC 200 HO follows a hull factor of 195 or it weighs 3300 lbs instead of the 3900 lbs as indicated in the table and the output of the 200 HO is 220 at the prop, then the speed prediction formula suggests that he should see 46.5 MPH. However, based on my own experience and JimH's reports, I'm sticking with my low 40s conservative prediction.

Here is one other thing that doesn't make complete sense to me. JimP reports his motor turning a 19P Mirage Plus to 5200 RPM. If he were using a 17P Mirage Plus, his motor should be able to turn that to 5600 RPM. According to Mercury, switching from the same pitch Mirage Plus to the Revolution 4 should cost 200 to 300 RPM at WOT. Thus, I would have expected the 17P Rev 4 to turn about 5300 to 5400 RPM at WOT. This is in fact what I have seen from my switch from the 17P Mirage Plus to the 17P Rev 4, a 200 to 300 RPM drop and about a 2 MPH slower speed at WOT. So I would not expect JimP's Merc to be able to turn a 17P Rev 4 more than about 5300 maybe 5400 if his motor can turn the 19P Mirage Plus to 5200, everything else being equal.

posted 09-18-2005 03:50 PM ET (US)            

Here is some more information on the speed prediction formula. Originally I was attributing this to Clark Roberts, as he was the first to mention it here, but it appears that this relationship between speed, horsepower, and weight is well-known to naval architects and marine designers as Crouch's Planing Speed Formula.

Crouch's formula is in a slightly different algebraic arrangement:

KTS = C / (LB/SHP)^0.5

where

KTS = Boat speed in knots

C = Constant chosen for type of vessel

LB = displacement in pounds

HP = horsepower at the propeller shaft

The speed predicted by this formula assumes a propeller has been selected that gives between 50 and 60 percent efficiency.

Of course, the secret is choosing the right value for C, and in Dave Gerr's excellent treatise on propellers, he offers the following values as guides:

C        Type of Boat--KTS
150 = average runabouts, cruisers, passenger vessels
190 = high-speed runabouts, very light high-speed cruisers
210 = race boat types
220 = three-point hydroplanes; stepped hydroplanes
230 = racing catamarans and sea sleds

To change the prediction to MPH versus KTS, a factor of 1.15 is applied, producing a table that looks like:

C        Type of Boat--MPH
172 = average runabouts, cruisers, passenger vessels
218 = high-speed runabouts, very light high-speed cruisers
240 = race boat types
253 = three-point hydroplanes; stepped hydroplanes
265 = racing catamarans and sea sleds

These values seem to reinforce the general wisdom of using a hull factor constant in the neighborhood of 180 for the Boston Whaler classic constant-deadrise v-hull.

posted 09-19-2005 10:37 AM ET (US)            

GPS was reading in knots, I checked it again yesterday. I always do everything in knots, but my dash speedometer is in mph and tops at 50 (a pitot tube - inaccurate at high speeds).

At 29.3 knots, the pitot speed is about 35 (a tad high). At 43.0 kts, the pitot is pegged at over 50. As I indicated, the pitot speed is an indicator of some speed in mph that is greater than knots. In this case, 43.0 kts equates to something over 50 on the pitot (which is inaccurate, but always reads more than the GPS in knots).

As for RPMs, they come straight off the the SmartCraft gauge.

posted 09-19-2005 10:57 AM ET (US)            

Now you're comparing apples to oranges. Jim Hebert has a Revenge 22 Whaler Drive, a significantly slower boat than a Revenge 22 with a notched transom.

A speed prediction formula is just that, a formula that predicts an outcome. It is interesting to me that you put more weight on a simplistic formula than actual real world results. Isn't that rather like putting the cart in front of the horse?

Teasing aside, I really think there is a simple explanation for all this and it may be as simple as knots vs. mph. It would be interesting to gather as much anecdotal evidence as we can and start comparing REAL data.

Jim Potdevin's boat and Pete Butterfield's are good starting points. I should note that Petdevin runs his boat in salt water. Butterfield ran his boat in Lake Washington here in Seattle which is freshwater and about ten feet above sea level.

posted 09-19-2005 11:13 AM ET (US)            

JimH. Interesting. I think the descriptions for the hull factors might be a little dated in light of what I've found for the 190 Outrage. Using the performance reports for the 190 Outrage published by Whaler (formerly known as the Nantucket), I determined that it has a hull factor of approximately 205. This higher hull factor explains why the 190 Outrage can go just as fast as the substantially lighter 18 Outrage with the same HP. I don't consider the 190 Outrage to be a "race boat type".

The reason the modern 190 Outrage has a higher hull factor than the classic 18 Outrage (205 v. 180) can be seen by comparing the hull shapes when they are out of the water, particularly the bottoms of the two hulls along the keel line adjacent the transom. The keel of the 18 Outrage carries the vee all the way back to the transom. I believe the deadrise for the 18 Outrage is something on the order of 16 degrees. In contrast, the keel of the 190 Outrage at the transom is quite flat. The 190 Outrage designers clearly incorporated a fairly large "planing pad" probably from the last 1/3 to 1/4 of the boat length to compensate for the extra weight. To my eyes, the stern hull profile is such that there doesn't appear to be any deadrise, quite uncharacteristic of an Outrage hull.

What does all this have to do with a Revenge 22? Quite a bit. The Revenge 22 hull shape is very similar to the classic 18 Outrage hull shape and, thus, it is equally as dissimilar to the 190 Outrage hull shape. Accordingly, one should not expect a Revenge 22 to have a hull constant approaching anything near 205.

posted 09-19-2005 11:45 AM ET (US)            

No jackplate. Engine was originally mounted in the middle and I moved it up 2 holes (3 would be the most).

posted 09-19-2005 01:36 PM ET (US)            

JimP -- OK, now we are getting somewhere. The 180 hull factor seems to apply most accurately to factory specified mounting height which I believe is only one hole up. If you are two holes up from there, then the raised engine plus a strong 225 (~240 HP) could account for some or maybe all of the significant performance improvement over predicted. My recollection is that your Optimax 225 replaced a Johnson 225. What was the top speed with the Johnson 225 when it was fresh? What hole mounting?

Tom -- do you have a reasonably accurate weight for your hull? Also, how high are the motors mounted, per factory specification?

With respect to the Whaler Drive, it is my observation that it does not appear to make a significant difference whether the Whaler is equipped with a Whaler Drive. The 180 hull factor seems to work either way. The speed of my 27 Whaler WD is very predictable using a 180 hull factor.

Interestingly, I used the 180 factor as a datapoint to buy my current 27 Whaler WD fitted with a pair of 225s. Prior to the sea trial the former owner told me that the boat would only go ~29 Knots (~34 MPH) at WOT and he was selling it because he wanted a faster center console. I myself would be disappointed with a 34 MPH top speed. In fact, at sea trial it went no faster than what he said but I also noticed it was listing bow down to the starboard and it was doing a lot of cavitating/ventilating. Believing that this 27 Whaler WD should do about 10 MPH better according to the speed prediction formula, I took a gamble and bought the boat after it otherwise passed the survey. After I took possession, I replaced a non-functioning trim tab pump (port tab was stuck all the way down causing the boat to list to the bow down starboard and the starboard tab was down some). I also aligned the outboards which were incorrectly aligned with a 1/2 inch of toe-out to about a 1/2 inch of toe-in which is within the specification for this boat (I had to have about 1/2 inch cut off of the engine tie bar). With those two adjustments, my 27 Whaler with the Whaler Drive is now performing within 1 MPH of the speed I predicted it would go using the 180 factor before I bought it.

By the way, I got a great deal on it and I'm sure part of the reason is that it was that a 34 MPH top speed was too slow for most prospective buyers that were not aware of how to assess the minor problem and incorrect setup. This cetacian specimen was just crying for help and I was only too happy to provide that assistance. ;)

posted 09-19-2005 01:57 PM ET (US)            

I got the boat with the 225 Johnson when they were 7 yrs old. Best speed was 41.5 kts or 47.7 mph. The engine was mounted in the middle hole (I think). Anyway, it was mounted lower than the Optimax 225.

posted 09-19-2005 04:29 PM ET (US)            

My boat weighs an estimated 5500 pounds as tested. The motors were mounted all the way down and at the factory recommended 29.75" engine spacing. The motors turn three bladed stainless steel props.

posted 09-19-2005 05:20 PM ET (US)         

All other things being equal, we know that prop choices matter, like the difference between an aluminum or Mirage Plus, for instance. The formula doesn't appear to compensate for this, but the difference is real.

I think Jim's chart shows my 25 Outrage with a max projected speed of 50 MPH. Here again, the forumla seems not to work.
I have run mne with several different sets of propellers, and speed differences were as much as 5 mph.

posted 09-19-2005 05:42 PM ET (US)            

The predicted speed is as sensitive to weight as it is to horsepower, just inversely so. The weight needs to be known as accurately as the horsepower if you want to verify the hull factor.

For Tom Clark's case:

LBS=5500
HP=300

Using C=180, the boat should reach

MPH = 180 * (300/5500)^0.5

MPH = 42 MPH

Using C=190, the boat should reach

MPH = 190 * (300/500)^0.5

MPH = 44.4 MPH

posted 09-19-2005 06:05 PM ET (US)         

I also remember that Louie Kokinis, with a pretty heavily rigged 22 Guardian, probably about the same weight as a recreational Revenge notched transom, has said here that he gets 53-54 MPH with a 225 Merc EFI. Louie carries a Merc 15 HP 4-stroke along for the ride, also. This would make sense, as the EFi has more HP than the Optimax. I thihk Louie is running a 4-blade Offshore/Vensura prop.

posted 09-19-2005 10:42 PM ET (US)            

At C=180 we get:

MPH = 180 X (300/5200)^0.5
MPH = 43.2 MPH

and at C=190 we get:

MPH = 190 X (300/5200)^0.5
MPH = 45.6

If the boat is a bit heavier, the range would be

At C=180 we get:

MPH = 180 X (300/5800)^0.5
MPH = 40.9 MPH

and at C=190 we get:

MPH = 190 X (300/5800)^0.5
MPH = 43.2

So with a reasonable error in the weight of 300 pounds (only a 5-percent error), we get speeds as low as 40.9 or as high as 45.6.

posted 09-20-2005 01:17 AM ET (US)            

Yes, I do run 19" props, non-counter rotating 14.25" x 19" Stiletto Advantage IIs to be precise. Peter is correct about that. The boat originally had a pair of Quicksilver aluminum props, also 19" pitch and to be honest, they could easily push the boat to 45 or 46 mph.

posted 09-20-2005 09:05 AM ET (US)            

We can deduce the proper constant C for a Revenge 25 notched transom from Tom's data. Rearranging the formula to solve for C, we get:

C = MPH / (HP/LBS)^0.5

Using Tom's data

MPH = 47.4
LBS = 5,500
HP = 300

we get:

C = 47.4 / (300/5500)^0.5
C = 203

But, again, this is only as accurate at the other measurements used. The speed measurement is probably the most accurate. The weight and horsepower could be off. If we assume an error of about five percent, our deduced value for C could be off by as much. If both the horsepower and the weight are off by in the same direction, the error multiplies and could be off by 1.05^2= 1.10 or ten-percent. This implies that the real hull factor could be as low as 180 or as high as 220.

In my own tests, it appears that the hull factor constant C for my REVENGE 22 WT WD was in the region of 180 to 190.

I'd say that you will be fairly close if you use values of C like

180 = classic Whaler Outrage V-hull with Whaler Drive
190 = classic Whaler Outrage V-hull with notched transom
200 = classic Whaler Outrage V-hull with set back bracket

posted 09-20-2005 10:13 AM ET (US)            

From what little information I can find doing a quick search, it seems we still have many in the 180 hull factor neighborhood. Newt's 20 Outrage, my 4 different Whalers ranging from 15 to 27+ feet(one with 2 different HP motors), JimH's 22 Revenge WD, Bulldog's 20 Revenge/twin 70s (formerly JimH's), all NOT located in the PNW, are classic Whalers having top speeds that closely correlate with hull factors of approximately 180.

What is also interesting is that at this old thread I found doing the quick search -- http://continuouswave.com/ubb/Forum4/HTML/000536.html -- JimP reports a consistent 44 MPH over 5 years for his 22 Revenge powered by the 225 Johnson. While that report isn't complete in that the weight isn't disclosed, under the assumption that the reported speed is achieved with a full tank of fuel that would seem to put it in the 180 hull factor ballpark prior to the repower and actual speed within about 1 MPH of predicted with a 225, consistent with my own experience. Anything less than a full tank of fuel would lower the hull factor with the assumption of 225 HP.

In that same thread, Swede5 reported a 22 Revenge achieving 41 MPH with a 225 and an aluminum prop, unfortunately actual weight is not known. I attribute Swede5's lower top speed to the difference in the performance of aluminum versus stainless steel propeller. As we all know, a stainless steel prop has less loss (more efficient) and so more of the propshaft HP gets transferred into forward motion instead of overcoming blade drag. My guess is that Swede would have seen 1, 2, or maybe even 3 MPH more, if using a stainless steel propeller. With that speed increase, the actual performance of his Revenge would have been reasonably consistent with the predicted speed using the 180 hull factor.

posted 09-20-2005 10:36 AM ET (US)            

Now you got me thinking about my old 225 Johnson (blew in Aug 2002), so I'm thinking back over 3 years. The 41.5 kts I was thinking it was doing was likely the 225 Optimax with 17" Rev-4 BEFORE I raised the engine, or it might have been the 19" aluminum 3-blade that came with the engine. I think I raised the engine in the Spring of 2004. Thinking back, the 225 Johnson probably topped at 39 kts - engine mounted low.

As for the Continental Divide... I bought my old 1982 Montauk with 1982 90 hp Evinrude on Eastern Long Island, NY. I trailered it to Kodiak, Alaska. In Kodiak it seemed about 2-3 knots slower than Long Island. I was back east a few years later and asked the dealer at the used boat place where I bought the boat about the differenece and his response was, "What was your altitiude?" How about sea level?

posted 09-20-2005 11:41 AM ET (US)            

You ought to go into politics given your ability to spin the data to fit the desired outcome!

I'll stick with facts. Let's look at the possible sources or error or variation you note above and see how likely it is in the case of my boat and its reported top speed.

I estimate that my boat when loaded with a quarter tank of fuel and myself weighs 5500 pounds.

The weight of a 1988 Revenge 25 Walk Through is supposed to be 4000 pounds.

Each 1989 Mercury 150 weighs about 400 pounds.

Two stainless steel props and two group 24 batteries weigh at least 100 pounds.

35 gallons of fuel weigh about 225 pounds.

I weigh about 175 pounds.

So how much is that? 5300 pounds.

But wait! What about optional equipment on board at the time? Let's see, stainless steel RADAR arch with rod holders and three antennae, GPS/sounder display, VHF radio, DGPS receiver, hydraulic auto pilot, raw water washdown, full width upholstered stern seat. Mills flying top and windscreen, Bruce anchor, chain and rode, fenders, lines, life jackets and throwable...

Let's be conservative and say all this weighs 200 pounds. That brings the total up to 5500 pounds. Does anybody really think I've overestimated the weight of my boat? Does anybody really think that if my boat actually weighs more it will go faster?

Furthermore there are many here who seem to think that Whaler under-specified the weight of these classic models and that we should take the published weight with a grain of salt and assume the boats really weigh MORE. I do not necessarily agree with that; if Whaler says my boat should weigh 4000 pounds, then that is what I am going to assume it weighs until I have evidence otherwise, but I do not think it weighs LESS.

I really doubt I am getting higher than predicted boat speed because my boat weighs less than I estimate it to. If anything, I have failed to account for some weight and it actually weighs more and therefore should have a LOWER top speed based of the speed prediction formula.

OK, maybe I'm cheating and my boat has more horsepower than 300. What do we think about that? Well, for starters my motors are 2.0 liter models, relatively small displacement by todays standards. Even Larry seems to think they do not put out more than their rated horsepower and if the guy who will claims owning a Mercury outboard will cure liver spots and return eye sight to the blind says that, I think that's it.

Furthermore my motors are 16 years old and have never been run in anything but salt water. Somehow I do not think that makes them extra powerful today.

So where does that leave us? "Hull factor"? Let me see if I have this straight. Most classic Whalers should use a hull factor of 180 in the speed prediction formula but the Revenge 22 and Revenge 25 mysteriously seem to need a much HIGHER factor to accurately predict their top speed?! Given that the 25 foot hull has the deepest Vee of any classic Whaler, I reject that assertion. If anything it should use a LOWER factor.

Propellers? I think it is only fair to include propellers that allow the motors to turn up to the upper half of the recommended WOT speed. Sure, I could put the prop from my 9.9 on these motors and I would get terrible speed results but I do not think I could then go and point out that it's "all in the props, this speed predicting thing."

First I read about how great this speed predicting formula is and how accurate it is and how if a guy isn't getting the speed that the formula predicts it will, the reported real world speed must be in error, not the formula.

Then I read about how there are so many variables and how these variables, if they are even just a little bit off will skew the predicted speed out of any useful range of results.

posted 09-20-2005 01:46 PM ET (US)            

The 25 Outrage's advertised weight is 3300 lbs. The 25 Outrage Cuddy's advertised weight is 3500 lbs. That 200 lb difference is the same as the difference between the 22 Outrage and the 22 Outrage Cuddy. That makes sense to me because the 25 Outrage Cuddy uses the same cabin cap as the 22 Outrage Cuddy. Thus, if that is all true, then I think the dry weight of the Revenge 25 should come in around 3600 lbs (300 lbs more than the 25 Outrage), rather than 4000 lbs because the 25 Revenge WT cabin cap is essentially the same as the 22 Revenge WT cabin cap.

Even if we were to knock the weight estimate down to 5100 lbs, that still doesn't explain the results that substantially exceed prediction with the 180 hull factor and it does make me wonder whether the 180 hull factor is appropriate for twins on a notched hull. Perhaps using 190 is more appropriate for twins? I don't know, not enough data.

However, far more often than not, in my usage over the years, the predicted speed formula has predicted speed within 1 MPH of actual speed using the 180 hull factor for ordinarily configured vee bottom classic Whalers, Revenge 22 notched and 22 Revenge WD included. See JimP's prior report with the Johnson 225 which I referenced above that falls within the typical 1 MPH deviation.

What started this whole debate was a challenge to what is perceived to be a low top speed prediction for a 22 Revenge with an E-TEC 200 HO based on using the 180 hull factor. However, if you take the time to look at the other datapoints collected over the years at CW, you'll see that the prediction of 42 MPH for 220 HP (3900 lb Revenge 22) falls in line with the actual speed reports on CW more often than not. No two boats or motors are exactly the same at birth, treated the same during their lives or run under exactly the same conditions, so there is going to be some variability. Even with this variability, the prediction formula really does give a reasonable prediction of top speed based on my experience.

posted 09-20-2005 03:30 PM ET (US)            

You may be on to something about the weight of the Revenge 25, but I'm not sure. One of these days I will weigh my trailer by itself and (hopefully) come up with a fairly accurate weight for my boat itself.

It still seems unlikely that for some strange reason Whaler would have OVERestimated the weight of that model and then UNDERestimated the weight off so many others (or some would have us believe.)

Twins vs. singles: I had wanted to make the point that horsepower delivered through twins is always going to be LESS efficient than a single because of the added drag of the extra gearcase and propeller blades. So in my case this only reinforces poor ability of the speed prediction formula to account for this and runs counter to the explanation that this somehow contributes to the boat having an apparently higher hull factor.

The speed prediction formula also has no allowance for any aerodynamic drag such as that caused by a RADAR arch or flying canvas. At full speed these two things contribute a LOT of drag and should be hindering my speed, not enhancing it.

posted 09-20-2005 04:13 PM ET (US)         

JimH's 22 Revenge WT Whaler Drive boat weighs 800# less than my full transom, bracketed 25 Outrage (using Whaler specs). Plus I have 375# of additional engine weight, for a total of almost 1200# more weight, and tend to have more fuel weight on board because the 25's tank is twice as large.

He is powered by a single carbed 1992 225 OMC, turning a 15" pitch OMC SST prop.

I am powered by twin 1997 Merc 200 EFI's, turning 23" Laser II props.

He gets about 40 MPH max top speed, and I get 60-62 MPH top speed, both lightly loaded. I also have a radar arch for added resistance. At crusing speeds of 25 to 30 MPH, with more weight and and an extra true 200 HP running through less efficient twin gearcases, we get the same 1.75 MPG. Actually, I think I really get closer to 2.0 MPG, but for the sake of discussion, lets say it is the same.

How could this be, and are hull efficiencies and hull factors the issue? Or do twin engines, indeed, IMPROVE efficiencies? I would stipulate that an EFI engine DOES get slightly better economy than a carbed engine, but not enough to make up this difference.

posted 09-20-2005 04:30 PM ET (US)            

We were talking about classic Whalers here, the 22 and the 25 in particular. You are not going to convince me that the typical 22 powered by a 200 or 225 is LESS efficient than the same boat powered by twins with the same total horsepower.

posted 09-20-2005 08:43 PM ET (US)            

Tom--I did not realize that your hull weight was all estimated. My hull weight is mainly measured weight, except that I take the trailer weight at the manufacturer's specified weight on the Manufacturer's Certificate of Origin (MCO).

I also think age can take some performance from an engine, so it is reasonable to think that a motor that is ten to fifteen years old might not run as well as a new motor. If there were anything about all the measurements and calculations related to my boat that I thought was a bit suspect, it would be the horsepower at the propeller shaft. If someone locally had a dynamometer I would love to hook it up to my motor and see what the real number for horsepower was. (I saw a used dynamometer for sale for about $5,000 some time ago and was thinking...what if...)

I think water and air temperature have an effect, for sure. One of the best performance runs I ever got was on a cold day in October where the air and water were much colder than most of the other runs.

Good research requires good data, so all of these reports about boats, weights, horsepower, and speed need to get sifted carefully for accuracy in measurement of ALL parameters. Just because the speed gets measured on a GPS to a reasonable accuracy does not mean all the other numbers are equally as valid.

posted 09-21-2005 08:47 AM ET (US)            

Here is a list of some classic hulls we have been talking about and their length to beam (L/B) ratios:

Outrage 17 = 2.59
Outrage 18 = 2.58
Outrage 19 = 2.64
Outrage 20 = 2.73
Outrage 21 = 2.91
Outrage 22 = 3.0
Outrage 25 = 3.07

Outrage 20 WD = 2.99
Outrage 22 WD = 3.26
Outrage 25 WD = 3.31

A wider hull will tend to be more easily driven onto hydroplane, and this may account for some of the variation seen between the results reported here.

posted 09-26-2005 02:40 PM ET (US)         

Running at 26 MPH cruise and 3000 RPM, MPG = 2.89
Running at 35 MPH cruise and 4500 RPM, MPG = 2.26

Top speed, at 5300 RPM, was 49.5 MPH and 1.33 MPG

I think these are very respectable economy figures, and show that powering close to max rating, and the 25' hull, can produce pretty good economy. The 25 Cuddy is pretty close to the Revenge in weight, and remember, this hull has Whaler Drive. The Yamaha 200's deserve a lot of credit also.

posted 09-26-2005 05:12 PM ET (US)         

"Performance measured with three persons aboard, 3/4 tank of fuel (that would be 105 gallons), 200# fishing and cruising gear. All measurements made with judicious use of engine trim."
They didn't give any indication of the weight of the factory tee top assembly.

My comments on speed were only based on considering a Whaler Drive (as a) bracket vs an Armstrong bracket, with the boat hull being the same on both.