Repowering 25' Bahia Mar

[Greg]

I'm considering a powering and hoping to hear advise from people who are more familiar with this hull than the engine dealers I've talked with.
The advise I've gotten from a couple dealerships have been contradictory. One tells me twins will cavitate in heavy seas another says a single will be a hazard when docking, The horsepower recommendations have been equally all over the map. The bracket manufactures tell me twins vs single is up to me while not offering much in the way of recommendations or sharing past results.

Aside from improved reliability with new engines I'm thinking outboards will provide easier/less maintenance and an additional 12 sq feet of deck space after removing the engine cover.

I'm struggling with two questions before I begin spending money

Mounting a bracket vs cutting the transom. The bracket looks easier but the question of weight hanging so far back and handling comes up. Cutting the transom solves the weight issue but I begin to lose some of the great deck space i just gained.

Single vs twins. I lean toward twins because I think the handling would be better but I could be wrong. I have had 3 blade props and four blade props on this boat, the 4 blade seemed to allow better low planning speed in the sloppy water so that makes me wonder if twins would be better than a single in the often sloppy lower Chesapeake, Pocomoke and Tangier Sounds.

All thoughts and advise is appreciated

Greg

[ktm_2000]

Hi Greg,

I'll tell you my story but it isn't worth much since my sorry A$$ can't find a motor to hang on the back of my B25 and tell you how it all turned out.

I had twin I/Os and they were long in the tooth and I decided to remodel. I went back and forth about a full bracket vs hung on the transom primarily waiting to see how CamB25's boat turned out. I liked the idea of getting the entire rear deck back but also did not want to go too far away from where the weight was originally.

I ended up doing the same short Bob's machine shop bracket which Cam did (I am not that original) and did a small motorwell on my transom. I chose the 10" fixed setback as Cam reported that he didn't use the lift all that much and am planning on a single 30" shaft motor. I lost maybe 8" of cockpit and built some storage on the transom and don't think the motor will be able to fully lift out of the water as a 300hp suzuki needs 24.8" and by my measurements I will have just about 22" to the wall of the motorwell. If the tilt isn't enough my plan is to hinge a portion of the back wall of the motorwell.

from the outside
https://photos.app.goo.gl/StcKTL34Cr23NxrG6

inside
https://photos.app.goo.gl/Dje15vRCgsdNGFPs7

[pschauss]

Matt,

Looks like you have done some really nice work there. I would be interested in seeing a side view.

[ktm_2000]

Peter,

Here's a top down view when I was putting the motorwell together
https://photos.app.goo.gl/28CRQuqebb1NBFcc9


Here's the overall profile view
https://photos.app.goo.gl/B7LcJNJ5v8PtW6Wy9

[CamB25]

The challenge with the B25 is that all power options are possible and they all can (and have) worked. It's tough to pick one! The decision is a little easier if you can pin down how and and where you will use the boat. My choice of a single outboard was made considering:
- shallow, saltwater operation
- in water slip storage
- easy maintenance
- no holes in the transom

But, it was not a simple bolt on effort. The water is ugly coming off the transom and, coupled with my 10" offset bracket, the engine height and prop selection are tricky. After 2 different 4 blades and 3 , 3 blade props, I've finally found a good one - Enertia Eco 18. This is a huge 3 blade at 16" diameter. Good hole shot, smooth cruise, and I'm getting 2.5 to 2.9 mpg according to the computer. A 17 would be better for top end rpm, but I can't find one. But, the engine has to be low...no lift with the jackplate or the prop will lose bite - rpms go up, speed doesn't. The point here is that there are a lot of variables and not all of them are independent.

One other note. The bow thruster I installed is the nuts. I wouldn't want to have just the single OB in my marina.

Cam

[ktm_2000]

Cam's post about prop depth is fairly important to me - when I install my bracket, I need to figure out the correct height then make the final marks lower so I have the option to raise or lower the motor by at least 2 if not 3 bolt holes on the outboard in order to be able to have some room to tune.

[Greg]

Thank you both for the replies and information.

I have read as much as I could find about conversions but it seems the final results or at least the required tweaking to get a decent ride are often vague. Cam's details about prop selection and engine height are just the kind of details I haven't seen. The bow thruster/handling comment reminds me that I really hate the Alpha drive shift mechanism, when docking an engine cutting out or the drive not coming out of gear is bad. I take it that if a big single engine is used a bow thruster should be strongly considered. I wasn't really looking to improve speed and fuel consumption but would welcome 2.5-2.9 mpg while becoming more reliable and gaining deck space!

The work I've seen on both of your boats is phenomenal! I am happy with the cabin and layout of the Bahia Mar so beyond the repower the refurb will be more about a 10' paint job done over the next two seasons. I have read and will heed the dangers presented by my sawz-all

I hope someone who has gone the Armstrong bracket with twins will offer up some of their experiences.

Br,
Greg

[CamB25]

The devil is always in the details. The absolutely simplest approach is to close out the transom holes and hang one or two outboards off the back. I would not use a fixed bracket, like Stainless or Armstrong. Why not?
- they are fixed. If you get it wrong, it's big work and $$ to correct.
- with a single engine you don't need flotation.
- accessing the swim platforms is still a climb over the transom- no benefit.
- Difficult to seal around curved areas of the transom.
- Is the water cleaner back there? maybe.
- skegs will live in the water - I don't think you will get them all the way out at full tilt.

For a bracket mount, the old engineer in me likes the port-a-bracket because it's very forgiving, adjustable, and easy to remove and replace. Soren in Denmark went this way on his boat - 300 Suzuki. Worked out for him. Yes, he installed a bow thruster for docking

For a non-bracket approach- cut the transom down to 30" (you have to plug the transom anyway, so not a big deal). Hang a single on a 4" jackplate. No splashwell needed (Cap't Bone). Jackplate will raise the engine 6" to permit out of water tilt and reduce the motor incursion into the cockpit. Easy, simple, adjustable, and much cheaper than a fixed bracket. If I had it to do over again, I would go this route in a heartbeat. I don't use the livewell I built. I could have rigged a Kodiak barrel to mount to one of my swim platforms when I live bait fish. Easy.

Be careful about weight balance. You have alot of weight forward with the Bahia. Pulling the old iron and replacing with a single will make the transom ride high. This is actually good news...you can hang a monster outboard, think Yamaha 425, and keep your balance right. Swing the biggest prop you can fit!

[ktm_2000]

Cam,

Don't second guess the livewell I used a cut down plastic 55 gallon drum with a hose that went overboard for years, I hated it, It needed to be in a stern corner and would tilt the boat under way. Sometimes it would shift and the outflow hose would end up in the boat and I'd be pumping 1100GPH into the boat only figuring it out when my bilge pump alarm went off because my old scuppers didn't move water quick enough and the lip for the engine box was quite low.

I use a livewell a lot so your mileage may vary but I expect my permanently mounted livewell to be a big addition to my fishing enjoyment.

[Greg]

The devil is always in the details. The absolutely simplest approach is to close out the transom holes and hang one or two outboards off the back. I would not use a fixed bracket, like Stainless or Armstrong. Why not?
- they are fixed. If you get it wrong, it's big work and $$ to correct.
- with a single engine you don't need flotation.
- accessing the swim platforms is still a climb over the transom- no benefit.
- Difficult to seal around curved areas of the transom.
- Is the water cleaner back there? maybe.
- skegs will live in the water - I don't think you will get them all the way out at full tilt.

For a bracket mount, the old engineer in me likes the port-a-bracket because it's very forgiving, adjustable, and easy to remove and replace. Soren in Denmark went this way on his boat - 300 Suzuki. Worked out for him. Yes, he installed a bow thruster for docking

For a non-bracket approach- cut the transom down to 30" (you have to plug the transom anyway, so not a big deal). Hang a single on a 4" jackplate. No splashwell needed (Cap't Bone). Jackplate will raise the engine 6" to permit out of water tilt and reduce the motor incursion into the cockpit. Easy, simple, adjustable, and much cheaper than a fixed bracket. If I had it to do over again, I would go this route in a heartbeat. I don't use the livewell I built. I could have rigged a Kodiak barrel to mount to one of my swim platforms when I live bait fish. Easy.

Be careful about weight balance. You have alot of weight forward with the Bahia. Pulling the old iron and replacing with a single will make the transom ride high. This is actually good news...you can hang a monster outboard, think Yamaha 425, and keep your balance right. Swing the biggest prop you can fit!

i still hope to hear from some Armstrong survivors but the above carries a lot of weight in my view. Would you still say that with twins? I'm thinking Suzuki 140's. They are in the HP range and seem to be geared for larger props.

[captbone]

I did years of research, tests, and observations asking those same questions. Even years later, I still think notch is best riding and performing.

Having said that, I am actively looking for a 31 Bertram to convert to a single outboard and am leaning toward a bracket or custom notch surrounded by a large platform. The goal is added room aft for use at sandbars. My use has changed and so have priorities for application. I love this bracket design especially with a single the surround would be much bigger.

[CamB25]

I think making the bracket more of an extension of the hull, like a euro-transom, is probably the safest approach. But that is lots and lots of work.

I see no reason for twins on the B25, and if I did, I would not bother with twin 140s. Twin 200s or 250s might be worth the effort. Come ride on my boat before you make the final call on twins.

'Bone - Single V12 Mercury outboard on 31 might be just the ticket!!

[John Swick]

One 300hp-350hp outboard on a porta bracket, or an inboard/outboard w/a dp outdrive.
KISS
Cutting down the transom on a B25 bahia mar is more complex because of the height of the cockpit deck.
The extra superstructure forward will help with the weight of an outboard hanging off the back.

A buddy of mine recently spent alot of money having a B25 sport convertible refinished and repowered to use around his place on the FL gulf coast.
Twin 150 or 200 Yammies on an armstrong bracket off the back and a bow thruster upfront.
They did a beautiful job inside and out.
The boat ran like a scalded dog, but he didn't keep it for long??
Last I heard, he had found and was having another one refinished, and was debating to notch the transom for a single outboard or go with a Volvo OceanX series small block HO package.
He really should go with the outboard because of all the skinny water he's travelling.
We shall see.

Good like with your project.

[ktm_2000]

Great point about the deck being higher..

Cutting down the transom on a B25 Bahia Mar is more complex because of the height of the cockpit deck.

This is what mine looked like before I fabricated the transom module and notched the transom. As far as I can tell a 30 shaft outboard motor needs to be setup where the top of the motor mount is about 1" down from the top of the bump out. I'm not sure how to work out the height difference of the deck of a Bahia Mar as I have not been on one, I have seen an express in person and remember the deck being fairly high up.
https://photos.app.goo.gl/LngocjA8m5XyJwbj8

[Greg]

I'll look closely at the deck height but it looks like the top of the transom cut would be flush with the deck.

I asked Armstrong for more info on installing on the 25, testimonials or possibly even contact information to get first hand experience. The replied try "The Hull Truth". I certainly thought a company building a fairly expensive custom bracket would do better than that. The local fabricator in Crisfield MD offered several names and places to see and hear how the brackets they build work out, they are looking better than any of the bigger manufactures I'm aware of.

Twins vs single...IDK. I see many want to put a lot of HP on their boat but if the "go to" repower is twin 3 liter Mercruisers at 135HP I'm inclined to think twin 140's weighing about 500 lbs. less could do the job well. If i used the 140's the costs are similar to a large single with a bow thruster and I retain redundancy. If i start upping the HP of twins a single becomes more attractive even adding a thruster. My goal was more about improved reliability and maintenance than increasing speed.

Cam, thank you for the offer, getting on your boat would be a thrill even if the battery was dead! If you were in the Baltimore Washington area I'd be there tomorrow.

The uncertainties of outcome more so than the costs have me rethinking about replacing my outdrives as my engines are running fine. Clearly that is the most cost effective solution and I get to keep the full transom and swim platform but the larger flat deck would have been nice. I am still hoping to find some first hand details with a setback bracket and twins.

Thanks to all for the thoughts offered.

[ktm_2000]

if you are interested in twins, please consider the Merc 150 four strokes that is based upon the 3.0L block. My uncle and one of my Buddies both have one and have had great luck with the motors. I've fished quite a bit on my buddy's 20' Seacraft and the 150 pushes it quite nicely and it sips fuel at a 24kt cruise at 3500 rpm, I think it is only burning @4.8 gallons per hour.

[John Swick]

My 1st B25, that I still have, is a 1963 sport convertible that was last repowered in the late 80's with Mercruiser 488's.
They are loud, and rough running until they spool up.
WFO is screaming (literally) right around 50mph.
It is heavy in the ass end (drain plugs in the scuppers are a must have) and not great maneuvering around the docks, but I can't justify tearing out good running equipment.
I'd love to replace them with a high output EFI/DFI small block v8 and a duoprop outdrive, but they've been 99% dependable and incredibly fuel efficient.
They require more annual maintenance then more current technologies, but the juice ain't worth the squeeze.

Probably because, I have another B25 sport convertible that I did repower with a 383 stroker @ 350 hp and B3 outdrive.
In comparison, this boat feels more responsive, balanced, is quicker, nimbler around the docks, and the cockpit is self draining as the scuppers sit ~3" above the waterline.
It is thirstier though, as I tend to cruise this one at 30mph to 40mph.
If I didn't have this boat, would I feel differently about repowering my '63?
Tough call, but yeah, if it was my only ride, and knowing what I know now, I'd probably do it.

Good luck.

[John Swick]

FYI
An acquaintance of mine and I both bought B25 Bahia Mars at the same time about 20yrs ago.
He repowered his with new twin mercuiser 4cyl 140hp i/o's.
I repowered mine with a new Volvo 8.1L 350hp/375hp and a duo-prop outdrive.
I never did not get a ride in his boat, but other acquaintances that have been in both have mentioned that the overall performance (not just top end) of my Bahia Mar was 'night and day' an improvement over his twin 4cyl set up.
With the modern technology we have today, IMO, I don't believe there's any validation to repower a B25 with twins.

[Greg]

Thanks John, more helpful information. Did you also add a bow thruster? Or does the duo-prop help that much around docks?
My boat has the same basic engines with 4 barrels rebuilt by a speed shop in New York and they make plenty of power for my needs. My alpha drives need to be rebuilt or replaced and that started me thinking about repowering. In the end two outdrives are short money relative to repowering and without much uncertainty.

[Jenks Mikell]

I repowered my 1962 moppie in 2019 with twin Susuki 200's and a stainless marine bracket. I am over the moon satisfied. I replaced the volvo 135 engines after numerous problems, mishaps, and lots of money. Finally said "uncle" and had them removed. Glassed in the back and put the bracket on. The rest is history. Initial intentions were to put 150's but was talked out of it. I have a good thread on this site titled "The Irene." I love turning the key and they crank everytime and are so quiet! This has actually been a ten year remake. As far as performance, my only complaint is that the boat chine walks. Hard to track on a straight line. I added 500lbs and seemed to help. Then remove 200lbs. I think I have found the sweet spot.

[beachbum]

Hey Greg,

I have a 25 SF with a single Mercruiser diesel 4.2 320hp from 2007 on a Bravo 2 leg from 1992. It is slow as I'm sure it's propped wrong (or there is the wrong gearset in the upper part of the leg). I get 25 knots WOT but she goes over the max rpm.

I think I could get around 28 knots by:
1) stripping off all the old antifoul and starting fresh
2) changing the prop or upper gearset to make the engine work a bit more or
3) change the leg to a Bravo 3x

Either way, it's considerably slower than most of the other guys - heayy engine, heavy leg. But, diesel which here in Europe makes a big difference in running costs.

[Jenks Mikell]

Couple of pics at the dock

https://imgur.com/yq0PswK
https://imgur.com/yfHRLFm

[CamB25]

Couple of pics at the dock

https://imgur.com/yq0PswK
https://imgur.com/yfHRLFm

Nice!!

[Greg]

Another beautiful boat! I am impressed with the skills and dedication many here put into their boats.

I love the comments about starting every time and being able to talk!

Jenks, like others I'm also interested in the weight placement along with the information about your bracket. I read its from Stainless, does it have flotation and is the setback 30"? After hanging the engines did she sit appreciably higher?

[Jenks Mikell]

Not sure of the set back. Thirty inches sounds right. The pictures show the foots in the water. They come completely out of the water. With about two inches to spare. Operator error on my part. Read the manual and figured out how to make them retract further. Plenty of clearance with the transom. The bracket is a watertight tank. So yes by that virtue, it does create floatation. I put weight in mid ships just aft of the bulkhead.

[CamB25]

Jenks - how did you solve your cavitation/bow down attitude issue from last year. Props and weight?

[Rocket]

Jenks, I have never heard of a 25 chine walking, I am a bit surprised. I run a B20 at about 65 mph and have never experienced chine walk. My previous B25 Sportfish with twin 318s was a 50 mph boat and it never did either.

Have you checked the tightness of your steering connection? My understanding is that chine walk is often caused by loose steering components and is the very slight "wiggle" that initiates and perpetuates the chine walk.

Not trying to sound like a know it all, but it may be worth checking.

[Jenks Mikell]

Cam, as for the cavitation and props, I did not change a thing. I did add a trim/tilt indicator and learned to drive the boat. Totally quit using the tabs except to maybe level the boat when I have too many people on board. Maybe your suggestion or someone's on this site.
Rocket, I have blead and blead and blead that steering system. It is very loose. The steering unit helm was brand new when installed. Other than replacing (total pain in the arss) or replacing sea star system at the motors, I am at a loss. Just replaced the simrad autopilot pump hoping that would solve. Nope! I was advised that with the upper station and lots of feet of hose connecting main station, upper station, and autopilot that a little slop should be expected from hydraulic tubes expanding. I called BS, but thats as far as I have gotten. Really enjoying the boat.

[Jenks Mikell]

Cam, just thinking about it, I did adjust the configuration of the motors. Adjusted 1/4 inch out or maybe in I can't remember. That made all the difference in the world. I received that advice by a prop guy in Fl who recommended that solution as I was looking to replace props.

[CamB25]

Interesting. Lot's of fine tuning needed to the boat and captain. I can relate to both. I too have pretty much left my trim tabs alone and use them only for small tweaks. Engine trim had a HUGE effect on my boat. Prop design would dictate this. The boat would not stand for trim with the 4 blade props...blow outs, rooster tails, VERY unstable at speed...general mayhem. The 3 blade props can take some trim, and my latest prop (Enertia Eco) likes alot of trim - up 35 degrees. I have about 100 hours on her and I'm still figuring it out, but I'm close to the "better is the enemy of good" threshold.

Ken at prop gods by chance? He has been great to work with.

You might consider power bleeding the steering hydraulics with a Power Purge system. It makes short work of the job. Evinrude demands it for bleeding my fancy, digital, sometimes working, integrated, very expensive to replace, thank God it was under warranty steering system.

[Rawleigh]

Jenks:. What type of steering? I own a 30 ft scarab sport with a friend and it always had problems with not wanting to run straight and hooking to the side. We thought it was chine walking. The bleeding instructions said not to turn it past the stop when bleeding. My friend got mad at it one day while bleeding it and cranked it over till he was bypassing fluid and that wound up burping all of the air out of the system. I think that sea star has since changed its directions to include this procedure. Some air remains in the bypass valves if you don't and that causes the problem. I can get detail procedures from him if you want. Last summer he changed to 300 Suzuki's with power steering, so we don't have that problem anymore.