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Author Topic:   Whaler Drives and Open Transoms
highspeed_jd posted 03-28-2004 12:51 AM ET (US)   Profile for highspeed_jd   Send Email to highspeed_jd  
I am still looking for a REVENGE 25, but I guess I am being picky. I want a closed transom boat because I want the extra fishing room. I have a few questions. If I buy a boat that has the SeaDrives on it, how much does it cost to install and Armstrong bracket? How reliable is an Armstrong bracket? If I buy a "fixer upper" and I want to close the transom, how would that affect the bracket and motor? Would that be a smart thing to do? Please if you have any input let me know.



jimh posted 03-28-2004 08:50 AM ET (US)     Profile for jimh  Send Email to jimh     
Here is a rough estimate of the costs involved in converting a Boston Whaler powered with OMC SeaDrives to an outboard bracket:

--Remove SeaDrives: $300;

--Repair transom holes with plywood and laminate, re-finish with gel coat: $700;

--Purchase Armstrong bracket: $4000 or more depending on design;

--Install bracket, rigging for engine cables, fuel lines, etc., new drains or scuppers in deck, new pumps, etc.: $1000.

TOTAL = $6,000

To this you have to add the cost of the new engines, their installation and rigging. For a REVENGE 25 you want at least a pair of 150-HP engines, so figure they will run about $18,000, and probably another $1,000 for propellers, gauges, rigging, and installation.

I'd guess you will be spending about $25,000 to re-fit an existing SeaDrive REVENGE 25 with a pair of 150-HP engines on an Armstrong bracket.

If you did all of the work yourself, you could save $3,000. But you would have to be capable of making proper repair to the transom so that it was structurally sound and cosmetically perfect, be able to design and order the proper bracket, then engineer its installation in the correct position, be able to hoist and install the engines, and accomplish all of their rigging. In short, you'd need all the capabilities of a well-equipped boat yard at your disposal and some good design and engineering skills.

To convert a standard transom Boston Whaler to a closed transom would be a similar task, except that you would have to construct the missing portion of the transom and re-build the whole upper half of the rear of the boat.

For some guidance on what that might look like, please review the article in Cetacea on this topic:

Reworked Full Transom Outrage

The $5,000 figure does sound like quite an expense, however one should view it in light of the original cost of the Whaler Drive option, approximately $6,000. The Brunswick Commercial and Government Products division (CGP) still offers the Whaler Drive option on the 25-foot hulls they build. The cost now is $10,000.

The high cost of the Whaler Drive option is probably one of the reasons that you do not find them on every 25-foot hull.

You ask: "How reliable is an Armstrong Bracket?"

Armstrong brackets are very well made, engineered from quality aluminum, and finished with excellent protective coatings. I have never heard of any failures of an Armstrong bracket. Inasmuch as in this case it will be retro-fitted to 15-20 year old boat, the concern ought to be more for the integrity of the transom on the boat than for the integrity of the Armstrong bracket.

highspeed_jd posted 03-28-2004 05:33 PM ET (US)     Profile for highspeed_jd  Send Email to highspeed_jd     

I was thinking that 115's would be enough, but you said that no less than 150's. My friend has a 25' outrage with twin 115's and it screams across the water. Would the cuddy make that much of a difference? Please reply back.


Or if anyone else has any info please tell me.

Plotman posted 03-28-2004 10:49 PM ET (US)     Profile for Plotman  Send Email to Plotman     
For the 1989 model year, whaler chareged $1100 more for a sea-drive blank model than they did for the standard transom in the Outrage 25.

I was just quoted $3300 delivered for an armstrong bracket for an outrage 22, designed for twin V-6s. My plan was to leave the transom open, but just install a rear seat and push it much farther back than normal.

Same security for passengers as a closed transom model, but you retain the ability to dump water if you take a breaking wave, and you avoid several thousand dollars of glass work.

A for you questiion about twin 115s on a 25. As long as you don't need to go 45, I'm sure they would move the boat. They will work harder at a given speed than a pair of 150s, and therefore not last as long. The most important factor, would be the ability to plane the boat on a single engine. Whaler lists 115 as the minimum needed to plane with a light load. Personally, I would not want to have to draw straws to see who we needed to throw over if I was out with 4 buddies.


alkar posted 03-29-2004 12:46 AM ET (US)     Profile for alkar  Send Email to alkar     
I have a 22' Outrage with whaler drive and twin 115s. It performs well, but it certainly isn't a hot rod, and it will NOT plane on one engine. With four big guys, 50 gallons of fuel, fishing tackle, and a 120 quart cooler full of ice and drinks, she'll do 40mph on the GPS.

I've run with a 22' Revenge with older, lighter, carburated Merc 115s, and it performed very well. I suspect part of that is that the Mercs are MUCH lighter than my four-strokes. They may also produce a bit more power than my Hondas, but I think a whaler driver equipped boat needs a little extra power. They're also rated for more power. (My 1989 boat is rated at 300 hp. The same boat was rated at 400 hp the year before my boat was built. The same boat without the whaler drive is rated at only 230 hp max.)

If I repower my boat I'll be installing AT LEAST twin 130s, and I'd probably go with 150s. A 25' Revenge with whaler drive runs well with twin 175s, and twin 200s would be a better choice.

LHG, if you're out there, how does your 25' run on one engine?

where2 posted 03-29-2004 12:57 PM ET (US)     Profile for where2  Send Email to where2     
Haven't finished break in with the twin 115Hp Yamaha 4strokes yet, so I can't say whether it will plane on one engine only (I suspect not). However, if you're not looking to run 50mph, anything from twin 115's to twin 150's should work on that hull with a bracket or whaler drive. The twins I described above are on a CPD 25' Frontier with a WD attached and 140 gal fuel tank. It's gotta weigh more than the 25' Revenge..., or close to what a Revenge 25 with the 175 gal fuel tank weighs...
LHG posted 03-29-2004 02:07 PM ET (US)     Profile for LHG    
A 25 Revenge WT WD is a 4250# hull if I remember correctly.
Considering the additional drag of the WD, I would not power one with less than twin 200's. Actually, I think the boat needs a pair of 225's. On this model, forget using a pair of 115's.

Although I've not seen any, I think an Armstrong bracket on a notched transom 25, Revenge or Outrage, would be a great performer, and look great also. The top of the bracket should be flush with the top of the transom notch, and the bracket designed to accomodate twin 25" engines, MANDATORY. Some water will wash over the top of the bracket when backing down, and some of this may spill over into the splashwell, which should be fitted with an 800 GPH pump. But the boat floor will not get wet.

Although I am much less familiar with the 22 hull, with all I have read here concerning twin 115 HP installations on the notched model and floor water, I am wondering whether an Armstrong on a notched 22 is wise, particularly with the weight of twin 25" 150's set back 26". I have never thought an Armstrong bracket offers much bouyancy support. It seems that the full transom WD really pays off for twin V-6's or 115 4-strokes on a 22.

As for HP on a 25, this is getting to be a hot topic of discussion here lately with the advent of 4-stroke 115's. Prior to that, practically "zero" 25's were powered with 2-stroke 115's, as the hull was clearly intended for twin 150's. I think it depends on the owners preference. Some like this arrangement, some don't. I recently ran into a fellow with a newly acquired 25 Outrage notched transom, running twin 25" Yamaha 115 4-strokes. The transom was nicely built up in aluminum, raising it 5". He liked the fuel economy, but not the performance, saying he hated running at 40 mph top end with the engines screaming at 6000RPM. At the same speed, my Merc 200 EFI's are loafing along at 3800 RPM. That's a huge difference in engine sound and wear at any cruising speed. When choosing power, I think cruising RPM are more important than pure HP or top end.

When selecting HP in twins such that one engine will plane off the boat, consider nothing less than max rating, or even excess rating a little. Remember, you will be attempting to run the boat with 4" MORE pitch than the engine would run as a single. This means considerable difficulty in planing. A lower torque 4-stroke complicates this even more. You need the highest HP engine available to get the rig going 4" overpitched, especially carrying the transom weight of the dead engine. A spare prop of 4" lower pitch can be carried, but you may not be able to get it on until you reach a dock or beach. Counter rotation further complicates the spare prop issue.

Andy, on both of my boats, one engine will plane them off, even with the 4" higher pitch. But it's not smart to run them full throttle overpitched like this (detonation), so here, once again, seemingly high excess HP is needed so the engine can be run 4000 rpm or less. Actually, with my highly reliable Mercs (!!!), I've never had to run either boat home on one engine.

highspeed_jd posted 03-29-2004 04:12 PM ET (US)     Profile for highspeed_jd  Send Email to highspeed_jd     
I appreciate all the helpful replies. I think that ya'll are right about the engines running more efficient and lasting longer at a lower RPM. But do you know if Armstrong makes a bracket that can hold twin 200's or better? That seems like alot of weight on the back end of that boat. LHG do you have a bracket on your BW? This is something I need to know before I get to deep into this project. Sorry I'm still wet behind the ears. I know someone that had an open transom 25'Outrage and he closed the transom and put twin 140 Suzuki's 4 strokes on an armstrong, but I've never been out in it. The boat looks great. But looks can be decieving. If ya'll have any more for me to learn about, please reply. I need it.

Thanks Again,


LHG posted 03-29-2004 04:58 PM ET (US)     Profile for LHG    
JD - See Cetacea page 11 and the Reference section on transom brackets. I have seen Armstrong brackets with triple Merc 300 EFI's on them. My 1997 Mercury 200 EFI's weigh 415# each.
alkar posted 03-29-2004 07:04 PM ET (US)     Profile for alkar  Send Email to alkar     
JD, My Honda 115's weigh the same as the Honda 130s (The 130 is the same engine without a stop in the throttle body). The 130 is the motor Evinrude chose for comparison with their newer injected 2-strokes. The Evinrude 135 weight less, produces more power, gets substantially better fuel economy, and produces lower emissions.

If memory serves, the Evinrude 135, 150 and 175 all use the same block, so you could have twin fuel efficient 175s for less weight than a pair of Honda 115s.

I'm not necessarily advocating for Evinrude. That particular comparison just happened to be fresh in my mind.

The Johnson/Suzuki 140s sound like a possibility. I have faith in the technology and construction, but I am concerned about the accuracy of the HP rating. I would look at the performance comparisons.

There are also some new 150 4-stroke on the market to consider.

Since most of our classics were designed and built before the proliferation of the mid-sized 4-strokes, they're not designed to carry all that weight that typically accompanies a twin 4-stroke installation. My boat is a good case to study. The boat was clearly designed for twin motors at about 350-375 pounds each. The former owner installed a pair weighing 505 pounds each. I love Honda motors, but my boat is not the ideal application for them.

Aside from an aft-heavy static trim, my boat appears to have suffered no ill effects. There are no signs of stress from the additional weight, so I wouldn't worry about being slightly over the recommended max weight. On the other hand, my boat would clearly perform better if she didn't have to overcome the enormous drag imposed by the additional weight pushing the whaler drive down. It's like having a fat guy standing on the back of your water ski.

jimh posted 03-30-2004 08:23 AM ET (US)     Profile for jimh  Send Email to jimh     
There is much good information about engine brackets in the Reference Section article:

Engine Brackets

rwill1 posted 04-04-2004 09:05 PM ET (US)     Profile for rwill1  Send Email to rwill1     
Haven't some folks mounted new motors to the existing Sea Drive mechanism?

I seem to recall seeing photos somewhere... Anybody remember this or am I deluded?

jimh posted 04-04-2004 10:50 PM ET (US)     Profile for jimh  Send Email to jimh     
Re fitting a new motor to an existing OMC SeaDrive mechanism:

I don't recall any mention of this. Send along a picture, it would be interesting to see, if one actually exists.

Many have discarded the SeaDrive, repaired the transom, and gone on to re-power.

andygere posted 04-05-2004 03:31 AM ET (US)     Profile for andygere  Send Email to andygere     
The powerheads and gear cases of OMC Sea Drives are essentially the same as comparable Evinrude or Johnson motors of similar vintage. I know of at least one 27 Whaler owner who has kept his Sea Drives running by replacing powerheads, carbs, etc. with Johnson parts. He has had more difficulty with the exotic tilt and trim mechanisms, having various hydraulic hoses and fittings custom fabricated.
LHG posted 04-05-2004 04:44 PM ET (US)     Profile for LHG    
Yes, I have seen entirely new OMC engines fitted into the Sea Drive mechanism. I think it amounts to removing the old engine at the tilt tube and fitting a new one on, minus the engine mounting bracket & built-in power trim, which the Sea Drive provides instead.

As mentioned, the actual Sea Drive parts are no longer supported, not the basically standard OMC engines, which they included.

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