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Author Topic:   Maximum Engine Weight
jimh posted 03-21-2004 03:53 PM ET (US)   Profile for jimh   Send Email to jimh  
Generally the classic Boston Whaler hulls were not rated by the factory for a maximum engine weight limit. Recently, newer recreational hulls designs have been given a specification for maximum engine weight. Certain hull designs from the classic era are still being produced by Brunswick Commercial and Government Products (CGP), and these hulls now have been given a maximum engine weight rating.

Using the current CGP hulls and their ratings as a guideline, it may be possible to develop a sense of the maximum engine weight rating for the older recreational hulls.

From the 2004 CGP Catalogue, I would suggest the following correspondences:

CGP Model / Maximum Engine Wt. / Similar classic hull
15 ALERT = 264 lbs. --> SPORT 15
17 ALERT = 330 lbs. --> MONTAUK 17
19 GUARDIAN = 470 lbs. --> OUTRAGE 18/19
22 GUARDIAN = 720 lbs. --> OUTRAGE 22
25 GUARDIAN = 970 lbs. --> OUTRAGE 25


Have any other maximum weight ratings been published in the past for the recreational hulls? (If so, please respond with those ratings and a citation of their source.)

What is the validity of extending these ratings from the commercially built hulls currently being produced to older, recreational hulls which may not be built with as much strength and laminate thickness?

Comments are invited.

Moe posted 03-21-2004 05:29 PM ET (US)     Profile for Moe    
Not that it makes any difference in the max motor weight, but a 1000 pound 17 Alert is a tiller-steer or side-console model, while the 1100 pound 17 Guardian is the CPD center-console equivalent of the RPD center-console Montauk.

For reasons of balance, I'd multiply the CPD max motor weight by RPD weight divided by CPD weight, or in the case of the 330 pounds of the 17 Guardian, by 950/1100 for 285 pounds.


Fishcop posted 03-21-2004 06:53 PM ET (US)     Profile for Fishcop  Send Email to Fishcop     
Well...I have been away and missed posting on the last exciting thread that was closed regarding Max HP rating.

I will leave you with this. If your vessel is rated for a maximum of 100HP/equiv weight, and you have a single 100HP/equiv weight motor, are you exceeding the max rating when you put on your 15/9.9hp kicker motor?

Dealers all over the world overpower and exceed the maximum transom hp/weight when installing aux motors on boats that have maxed the hp/weight on the primary motors.

Just my thoughts while out in the briney deep.

[Andy--different topic--engine weight not rated horsepower--jimh]

kamie posted 03-21-2004 07:29 PM ET (US)     Profile for kamie  Send Email to kamie     
How could you ever hang twins and come close the the max motor weight? Even if I wanted to put twin 75Hp Merc Optimax (total HP 150) they are 375lbs each, for a total of 750lbs, not including rigging ect. Well above the current suggested max of 470lbs for the guardian.
jimh posted 03-21-2004 07:33 PM ET (US)     Profile for jimh  Send Email to jimh     

If I follow your example, you are suggesting that the ratings for imputed maximum engine weight ought to be scaled for all models by using a ratio that is proportional to the dry hull weights of the two hulls.

This would have the effect of decreasing all the of the imputed maximum hull weights for the older recreational hulls.

Perhaps you could do this for us.

Here are the weights of the CGP hulls from the 2004 catalogue

15 ALERT = 615 lbs.
17 ALERT = 1000 lbs.
17 GUARDIAN = 1100 lbs
19 GUARDIAN = 1750 lbs
22 GUARDIAN = 2550 lbs
25 GUARDIAN = 3574 lbs

And for the equivalent recreational hulls

15 SPORT = 580 lbs. (1990 catalogue)
17 STANDARD = 850 lbs. (1999 catalogue)
17 MONTAUK = 950 lbs. (1999 catalogue)
18 OUTRAGE = 1250 lbs. (1990 catalogue)
22 OUTRAGE = 2050 lbs. (1990 catalogue)
25 OUTRAGE = 3300 lbs. (1990 catalogue)

Well, wait a minute, here is the problem! What weight do we use for these hulls? Some were rather notoriously under-listed in weight.

Also, laminate added to the bow does not necessarily make the transom stronger. One could argue that the added weight of the commercial hulls might even reduce the maximum engine weight rating of those hulls.

By the way, the ratings from Brunswick CGP for the ALERT 17 and the GUARDIAN 17 are the same for MAXIMUM HP and MAXIMUM ENGINE WT.

Moe posted 03-21-2004 08:47 PM ET (US)     Profile for Moe    
[Adapted the Spreadsheet sent by Moe--jimh.]

Compiled by Moe
15 ALERT 615 264 SPORT 15 580 249  
17 ALERT 1000 330 STANDARD 17 850 281  
17 GUARDIAN 1100 330 MONTAUK 17 950 285  
19 GUARDIAN 1750 470 OUTRAGE 18/19 1250 336  
      OUTRAGE 18/19   434 1616
22 GUARDIAN 2550 720 OUTRAGE 22 2050 579  
      OUTRAGE 22   665 2355
25 GUARDIAN 3574 970 OUTRAGE 25 3300 896  
Published Values Calculated Values

The 18/19 and 22 Outrage published hull weights are grossly (500 lbs) lighter than their CPD counterparts.

I used those published weights AND calculated estimated weights for them, based on the proportion of the 25 Outrage/Guardian 25 weights.

So the these two boats have two lines on the chart.


jimh posted 03-23-2004 08:07 PM ET (US)     Profile for jimh  Send Email to jimh     
With regard to the maximum engine weight that one could perhaps infer for older recreational hulls, I don't believe there is any particular value in the methodology of reducing the engine weight ratings on the recreational hulls in proportion to the lighter weight of those hulls as compared to the commercial hulls.

My thinking is along these lines. The hulls are rated for the same horsepower. From this I infer they must be similarly strong. If the horsepower rating is the same, one cannot say the recreational hull is insufficiently strong to accommodate the engine horsepower.

The ability of the hull to accommodate engine weight is more of a function of the hull's form, not the hull's weight. The hull form in these cases is identical. Thus I think it is really quite valid to argue the exact opposite of the notion proposed (that the lighter hull can accommodate less weight). If the hull itself is lighter, then the hull form's reserve buoyancy is greater and it would be able to accommodate more weight, not less weight.

The laminate schedule for the recreational hulls has proven to be more than adequate, as witnessed by many 20-year-old (or older) hulls that are in perfect condition and without any structural damage.

As for the strain on the transom from supporting an engine, the static weight of the engine is probably not as significant as the horsepower. Consider that the transom is the point of attachment of the forces propelling the hull. When 200-HP of force/thrust/work is being applied to move the boat, all of this force is being transmitted via the transom. My intuition tells me that this is a greater burden and stress than the static weight of the motor sitting on the transom.

Therefore, my current thinking is that the weights I proposed in the initial article in this thread are probably reasonable guidelines. I don't see a compelling reason to reduce them in proportion to the difference in hull weights between similar commercial and recreational models.

linust posted 03-23-2004 11:22 PM ET (US)     Profile for linust  Send Email to linust     
How many have actually scaled their classic whalers? Did my Revenge 22 WT WD really weight 2600# dry? Or was it more...I know Whaler had some "challenges" listing accurate weights for some of their hulls (the 23' Conquest comes to mind, with the '99 brochure listing it at 2900# and the 2000 brochure at 3650# for the same boat!)

I'm intrigued/troubled by the disparity in the current published CGP weights vs. the 1990 published weights for recreational products. Workboat (commercial) layup was supposed to be 10% more glass/resin...some of the numbers Jimh shows are as much as 40% more (! for the 18/19 hull), though some are as low as 5 or 6%...for the 22 Outrage, 20%. wow.

Anyone have any actual weights for their boats, and under what config (empty/full fuel, oil, which engine, prop, etc).

Bigshot posted 03-24-2004 01:21 PM ET (US)     Profile for Bigshot  Send Email to Bigshot     
I thought the 02 brochure stated Montauk(old style) weight was like 410lbs max.
jimh posted 03-25-2004 09:16 AM ET (US)     Profile for jimh  Send Email to jimh     

Yes, you are correct. In the 2002 Boston Whaler boat catalogue they confusingly call the classic Montauk 17 boat the "170 MONTAUK" (even though almost universally now that designation is used to refer to the new boat introduced in February of 2002 which also bore that name.)

In the specifications page the maximum engine weight is listed as 410 lbs.

Thank you for that citation, it had escaped my notice previously.

It is interesting to compare this to other values, thus:

Factory rating = 410 lbs.
CPD rating = 330 lbs. (de-rated 20%)
Moe's rating = 285 lbs. (de-rated 30%)

It looks to me like the CPD ratings are already very conservative. If one were to use them as a guideline for the maximum engine weight ratings on older recreational hulls, it appears that these figures would be, if anything, on the low side of what the hulls can actually accommodate.

Moe posted 03-25-2004 10:33 AM ET (US)     Profile for Moe    
The 410 lbs in the '02 brochure probably goes along with the 170 name that got out there early. That's the max weight of the new, much larger Montauk.


Tom W Clark posted 03-25-2004 10:43 AM ET (US)     Profile for Tom W Clark  Send Email to Tom W Clark     

No, that's incorrect. Nick has it right. The 2002 catalog is the first to have maximum engine weights for all the recreational models, including the classic Montauk.

The 2002 catalog clearly states this information and shows the classic Montauk. I also remember the Whaler web site at the time had this same information in the year before the introduction of the new MT170.

As anybody who has owned a Montauk with a V-4 outboard and a kicker can attest, the Montauk can easily handle over 400 pounds on the transom even with a couple batteries in the back of the boat too.

Moe posted 03-25-2004 10:46 AM ET (US)     Profile for Moe    
BTW, my derating is just based on balance, which will affect the handling of the boat. Despite the same hull form, a 330 lb motor should have the RPD boat sitting a bit more bow high/stern low than on the heavier CPD, where it's less of a percentage of the total weight.

And despite my derating, I believe the 305 lb, 90 HP E-Tec is about as perfect a green motor as you're going to find to repower the classic Montauk. The 235 lb 60 HP E-Tec is only slightly heavier than the 2-stroke 60/70 Yamaha, and looks good for the 15 Sport.


Tom W Clark posted 03-25-2004 10:58 AM ET (US)     Profile for Tom W Clark  Send Email to Tom W Clark     

No, a kicker motor's horsepower is not combined with the main motor's horsepower for the purpose of calculating total horsepower on a given hull. That is because only one or the other motor is propelling the boat at any given time.

To get back to Jim's original post:

No, there were no maximum transom weight ratings for classic Whalers before 2002.

The difference between the recreational hulls Maximum Transom Weight and the CGP hulls Maximum Transom Weight is not simply the difference between the dry weight of the hulls. It also has nothing to do with the strength of the transom itself.

The difference is how the boat floats. To use an example, the Guardian 17 has scuppers in the rear of the boat to allow large amounts of water that has come onboard to escape easily. Those scuppers do not entirely prevent water from seeping back into the boat if the scuppers are below the waterline (this is one design feature of the some Post Classic Whalers like the Dauntless 14 that I think is very poor).

A heavy motor in conjunction with the added weight of the heavier 'glass lay up will put those scuppers under and the boat will no longer be truly self-bailing.

jimh posted 03-26-2004 08:56 AM ET (US)     Profile for jimh  Send Email to jimh     

Could you please clarify this question:

Do the CGP Versions of older recreational boat hulls generally have a different cockpit drainage system?

By different, I mean other than the typical cockpit sump located on the outboard starboard side of the rear of the cockpit in front of the engine slash well dam (or twin drains like this, one on each side).

Are the CGP versions equipped with cockpit scuppers that drain directly to the sea and are intended to be left open at all times?

Thanks in advance for your added insight.

Tom W Clark posted 03-26-2004 09:03 AM ET (US)     Profile for Tom W Clark  Send Email to Tom W Clark     

Yes, that is precisely what I mean.

Examine the CPD (CGP) catalogs on the Boston Whaler Catalog Collection and you will see numerous photos of these scuppers installed on the boats.

I do not, at this time, have a complete breakdown as to which models and years of commercial Whalers were fitted with the large scuppers. I will do some research and let you know.

gnr posted 03-26-2004 10:10 AM ET (US)     Profile for gnr    
My 1987 Guardian-17 has a single drain tube from the sump in the center of the aft cockpit area through the transom. No scuppers.
jimh posted 03-27-2004 03:20 PM ET (US)     Profile for jimh  Send Email to jimh     
[Adapted the Spreadsheet sent by Moe and added it to his article above.]
Moe posted 03-27-2004 03:38 PM ET (US)     Profile for Moe    
Nice job with the spreadsheet, Jim. Thanks.

LHG posted 03-27-2004 04:12 PM ET (US)     Profile for LHG    
Would the Commercial people tell me I couldn't order a new 19 Guardian with a pair of nice Merc 75 2-strokes on it? (303# each)

I think the answers needed in this discussion have to come from BW, as any other means to dicipher these weight limitations doesn't make much sense. Trying to apply mathematics to apparently arbitrary decisions, perhaps based on liability/insurance concerns (my best guess), doesn't work very well. Marketing concerns with competitive engine weights could also be factors.

The advent of all the heavy, clean engines, now available for powering 25 year old hull designs, is probably part of the equation, with the old notion of just HP controlling, now becoming increasingly irrelevent, and creating possilbe problems.

Take the 18 Outrage/19 Guardian, clearly designed for twin engines up to 150HP total. The lightest pair of clean 75's I can find, made by Mercury of course, since that's all they'll put on it, are 360# each (75 Optimax). This is clearly pushing the load limit on the hull, although I think it would handle it. I've been running my 18 around for 18 years now with 610# of engines on it, set back 10", so I know the hull can handle that load quite easily. So will CGP sell a 19 Guardian with twin 75's on it? Maybe this is little hidden profit center - you have to pay more for a "beefed up" transom. This has been used in the past where they have put twin 150's on a 22, or twin 200's on a 25.

The 470# load limit on the 19 Guardian also, quite coincidentally (?), excludes the new Yamaha/Honda 150HP 4-strokes, but nicely allows for the Merc Optimax 150. So the buyer is disarmed who wants a 4-stroke Yamaha 150, and easily convinced to take the Merc.

Perry posted 03-27-2004 11:35 PM ET (US)     Profile for Perry  Send Email to Perry     
The Yamaha F150 4 stroke is 466 lbs. so it would be slightly under the 470 lbs max limit for the 19 Guardian.
Moe posted 03-27-2004 11:40 PM ET (US)     Profile for Moe    
Not with oil and a prop, especially a stainless one.
Perry posted 03-28-2004 12:13 AM ET (US)     Profile for Perry  Send Email to Perry     
Which brings up another question: Does the max engine weight specification refer to the engine manufacuturer's listed dry weight or the weight after the buyer adds oil and prop?
LHG posted 03-29-2004 02:41 PM ET (US)     Profile for LHG    
What does the F-150 weigh in 25" shaft?
Bigshot posted 03-29-2004 03:05 PM ET (US)     Profile for Bigshot  Send Email to Bigshot     
LHG....usually about 10lbs more.

Some manufacturers weigh dry, some weigh wet. May want to e-mail the company if not stated in their brochure.

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