Fishboat Conversion

Discussion in 'Powerboats' started by Guest, Oct 10, 2002.

  1. Guest

    Guest Guest

    Although I've spent most of my days in planing boats I'm considering joining life in the slow(er) lane. I've been looking into displacement or semi-displacement boats for cruising the Great Lakes and possibly farther at some point. In all cases I'd be sticking to the "coastal" variety of cruising. I don't plan any bluewater voyages in the short term. As I read a number of books on hull design, power requirements & economy, stability........I'm beginning to focus on Lobster/Cape Island/Novi hulls. I'd favor a dry exhaust, keel cooled, naturally aspirated diesel for power. LOA would be in the 32-36 foot range. An NA diesel would put the boat in the 1.5 S/L range or less.

    There are plenty of boats available in the 'lobster yacht' class though they all typically have fairly high hp turbo diesels to reach the 20-knot max people look for in these boats. As I look around for all types lobster type boats I keep coming back to Cape Island hulls out of Nova Scotia. I've located a ton of available commercial longliner fishboats. Many of them seem to have the mechanical setups I'm looking for with smaller diesels and larger fuel tanks, dry exhaust, keel cooling..... Many have larger wheelhouses that could be used for some living accommodations, besides the future 'stateroom' down below. They often have a fairly healthy beam for their length (L/B around 2.6-2.8). The boats are registered in the 12-20 tons area, I'm guessing the actual displacement will be in the 14,000-18,000 lbs range. The fish holds are around 10,000-20,000 lbs. Naturally the Canadian/US exchange rate helps make these boats inexpensive(?).

    Question(s): I'm considering buying one of the 34-36 commercial cape island fishboats and converting it to pleasure use. I love the design and the basic utility character of these boats. Though I haven't sea trialed a boat like this I understand they are known as good seaworthy & seakindly hulls. I would get a very good survey prior to purchase. The conversion to pleasure use would partly be done by a boatyard and partly by myself. I like to work on projects like this. Am I nuts? Can anyone give me an idea of what I might expect in a conversion like this(sound proofing, heating, adding a small galley & head/shower, water tanks......)? Would fishboats like this be so 'rough' in finish that converting them to pleasure use would cost more & be more trouble than it's worth? Would such a converted vessel be worthless to anyone but me? Would I be better off to just have a boat like this built new? I know this are questions that are hard to answer by anyone but me, but what would you do?

    I'm considering hiring professional help of somekind (no pun intended) to help weigh the questions, work, and costs ahead. Any help you could offer would be greatly appreciated.

    Here's acouple pics of basic boats that are close to what I'm thinking about:

    This one is a 1984 fiberglass, 34' 11" x 13' 6" x '4 6" (10' 6" at the stern). Powered by a 140 hp 4-71 DD.



    This one would be my first choice on looks alone. It's said to be a 1965 36 x 13' 5" 'fiberglass/wood" hull. No idea(yet) if this means a GRP hull with wood interior framing or if this is fiberglass over a wood hull. It has a gas GM 144hp engine (fresh power may be a must on this one)



    Any thoughts? Is it advisable to hire a naval architect for advice?
  2. MDV
    Joined: Feb 2002
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    MDV Junior Member

    The first things that come to mind are:

    1. A Naval Architect can assist in a lot of aspects, and will probably be worthwhile.

    2. I'm not familiar with these type of vessels, but the addition of permanent ballast instead of the cargo they normally carry will perhaps give better seakeeping and stability characteristics for pleasure use.

    3. Be carefull of the cooling capacity of keel cooling, if the boat is designed for cold waters, then you may have problems if venturing to warmer climates.

    4. As you mentioned, a proper survey for such boats is a must. They are often work hard, and you never know what you will find with such old boats.

    5. Check if the boat still is under commercial survey, if not check why the certification has been removed. It may help in finding major problems (if any).


  3. mmd
    Joined: Mar 2002
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    Location: Bridgewater NS Canada

    mmd Senior Member

    Hello, Guest. I am a practicing naval architect in Lunenburg County, Nova Scotia. I grew up on these types of boats and have both intimate knowledge of and high regard for the type. No, you are not nuts, but you do require careful selection of the boat you want. These are, after all, working boats and some have been better built & maintained than others. I agree with the survey, it is a must. The blue-hulled vessel in the first photo is a later style of Cape Islander, one that has evolved with higher freeboard to make it more versatile for various types of fishing and capable of going farther offshore for pelagic and bottom fishing. The second hull is an older style hull and is traditional plank-on-frame with a sheathing of FRP to extend the life of the hull. It evolved at a time when these types of boats were used mostly for inshore lobster fishing and have very low freeboard to make it easier to haul the lobster trap aboard. This type is very pretty (IMHO) and makes a very stylish coastal cruiser. One has to be careful about selecting the right boat, though, as there are a few spots in the hull that are prone to getting weak as the boat ages. There are good ones out there, it just takes a practiced eye to know what to look for. I would be happy to assist you in locating a Cape Islander worthy of conversion and in advising you on the strengths and weaknesses of the type. Contact me offline if you would like to discuss this further.
  4. fishboat
    Joined: Oct 2002
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    Location: Southern Lake Michigan

    fishboat Junior Member

    MDV/MMD, Thanks for the replies and thoughts (I registered, but somehow the post came through as 'guest').

    I did consider the permanent ballast as the cargo these boats would carry would have to be considered in their design. This is sort of(?) like adding some weight to a 3/4 ton pickup to make it ride better. I do wonder what the hold looks like & it's dimensions. Space on a boat is always at a premium...the hold space could be interesting. The cooling in cold water & certification are great ideas. I hadn't considered either one. The blue hull is a working longliner today. I'm guessing the older boat was retired from real work some years back. The lines of that boat just make me want to say "arrggh!"

    MMD, You could be the person I'm looking for. As I dig out info on Nova Scotia & its boats the area itself sounds like it would be a great place to visit. I'll be in touch.
  5. mmd
    Joined: Mar 2002
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    Location: Bridgewater NS Canada

    mmd Senior Member

    The older style of boat carried very little cargo (it doesn't take very many lobsters to make a day's fishing worthwhile) except at the beginning and end of the season when they are setting/recovering their traps. Due to this, the older style boats do not have a cargo hold - they carried their bait & catch on deck in fishboxes. Ballast will not likely be needed - the mass of your added systems and structure to create a lobsteryacht will more than compensate for the removal of fishing gear and catch. The boat's form will provide the stability you need, unless you try to make a multi-deck wedding cake out of the vessel (not advised).
  6. Jeff
    Joined: Jun 2001
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    Location: Great Lakes

    Jeff Moderator

    For what it's worth, problems with staying logged in on the forums are most commonly due to cookie issues with your browser or your privacy/security settings denying cookies from our domain ( or But it could also just be a one-time glitch.

    Should be a very interesting project!
  7. 8knots
    Joined: Feb 2002
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    Location: Wasilla Alaska

    8knots A little on the slow side

    Warning!!!! Maybe......

    Hello There
    Here are a few cents from a fellow boat nut! I will post a pic of a
    110' wood tug that is/was for sale in AK. For $75.000 US Cheap
    right? When I first saw her I decided to sell my soul for her, Wow 110' Of working tug for so little money Twin 1700 Hp enterprises
    2 4-71 gens 16,000 gallons fuel. A real man boat with the big wheelhouse and monster engine room to boot. Luckily my wife
    (the smart one) From listening to my ranting over the years brought me back to the reality of the financial obligation and the endless hours painting, scraping, fixing fixes made 10 years ago with dt and bailing wire. The Cutlass bearing alone will run afew thousand dollars whatabout the haul-out.. The boats you are looking at are smaller but maybe the same principles apply. Would you rather be cruising/fishing or in coveralls for 12 weekends in a row chipping bottom paint. I feel this lesson every summer when everybody cruises in there restored hotrods and my 1948 Chevy Suburban sits in pieces for the 4th year.
    I am not preaching dooms day but do have the Survey done
    And don't be blinded by the good deal! 8Kts

    Attached Files:

  8. fishboat
    Joined: Oct 2002
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    Location: Southern Lake Michigan

    fishboat Junior Member


    Thanks for the thoughts & I hear what you're saying, but I have enough grey around the temples (or maybe in my beard) that 'the fever' doesn't get me anymore. The days where "I must have at any price(or commitment)" are long gone...been there, done that & was fortunate to find another person with the fever such that I only 'lost' around 4% after three years of ownership. The experience was a good enough shot across the bow though.

    What I lack in understanding of such a project I can make up for I a sharp pencil, research, planning, and the ability to admit the figures just don't add up. The key here is to give proper weight to the intangibles(emotion, pride, downright fun of owning & operating an 'original'...) along with the known costs of doing a conversion. The cost of commercially available lobster yachts relative to the base cost of one of these boats does give one pause to at least look into what I'm considering. I personally would place more value in the older(yellow) Boudreau hull in fine condition than a teaked & tweaked out Duffy & Duffy, but that's me. :)

    As much as I like tugs and tug-style cruisers (I've looked at a number fo them) the one you mention isn't a good deal at $75K...not even for free(unless you needed such a workhorse). Feeding twin 1700 hp diesels is enough to sadden anyone's day. It would be good for visiting some island & towing it home though...that's a monster boat. One of those 4-71 gensets would be plenty of main power for a good cruiser. You made a good choice.

    Here's an example(a bit beyond what I'm thinking about) of a 50 x 13 wooden hull that spent it's first 24 years fishing cold water for a living. It now has some FRP sheathing and a whole new look. It now glydes along at 9 knots via a 110hp Volvo. The conversion was done by Canmar International of St. Johns, Newfoundland. A beaut.

  9. 8knots
    Joined: Feb 2002
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    Location: Wasilla Alaska

    8knots A little on the slow side

    Hey FishBoat
    I am with you on the smaller boats (a reality boat)Here is a sketch of my one day coastal cruiser. I will be in a walker when she is done, But hey Im a slow poke kind of guy anyway.
    Good luck with your project 8Kts
  10. Brian Smith
    Joined: Apr 2003
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    Location: Vancouver Island

    Brian Smith New Member

    Constant Velocity Joint Drive Shafts

    I am planning to purchase a diesel, 32 to 37 foot, fibreglass hulled fish boat and convert it into a pleasure boat. So that I can consider a wider selection of boats, I would like to have the option of using a “constant velocity joint shaft” with a thrust bearing which would give me some flexibility in engine placement and reduce noise from engine vibration. Does anyone have experience with these systems?

    (see the Aqua Drive system at )
  11. gonzo
    Joined: Aug 2002
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    Location: Milwaukee, WI

    gonzo Senior Member

    If you need any advice or a survey in a boat you are considering buying, I am located in Milwaukee. I can travel anywhere though. Also, if you need plans for modifications or an estimate for the job, I can help you with it.
    Joined: Oct 2002
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    Location: Conn in summers , Ortona FL in winter , with big d

    FAST FRED Senior Member

    Navy 50 Launch

    Have just purchased a Navy 50 ft launch built in 1967 buy Uniflite.

    So far we have only done a delivery from Camden Maine to Portland (Middletown ) Conn.

    She is powered with an orig 1943 Grey Marine 6-71 & 3 to 1 Twin Disc , that started life as 50ft tank fuel lighter.

    Hull speed of about 8K is easily done at 1500 with a measured (sort of ) consumption of 3.3 GPH.

    Thats a very light load for a 225 hp engine.

    Does anyone have a BMEP or fuel map for these fine old engines?

    I will switch to smallest injectors that will not require retarding the timing from the advanced factory setup.

    She now pumps the equivalent of N 90 , and I think there would be enough power with 65's.


    For those interested the Navy 50 hulls are great for a conversion , the scantlings for the hull are truly ocean grade , so a Blue Water Trawler could be done , with a robust enough deck house.

  13. badges65
    Joined: Dec 2002
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    badges65 Junior Member

    is this a high block or low block engine?
    2 valve or 4 valve head?
    what are the actual injectors??
    Joined: Oct 2002
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    Location: Conn in summers , Ortona FL in winter , with big d

    FAST FRED Senior Member

    6-71 FUEL MAP

    The 1943 engine is listed as 64 HN9, and although the injectors carry a letter ID , there N-90's in todays terms.

    Only a 2 valve , as I think the 4 valve came a decade or two later.

    Rated Specs are 225hp at 2100, but in the SL range we can afford to run (about 8K) the burn is 3.3 GPH at 1500 and about 3.8 at 1600.

    My estimate is 3.3 GPH is about 53 hp

    And 3.8 would be about 60 hp , using 16 HP per gal //per hour , which may be generous for a DD.

    Can you post a BMEP map for this engine?


  15. Peter_T
    Joined: May 2003
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    Location: Gulf Coast

    Peter_T Junior Member

    Both ex. boats on display show the pilot house in a extremely low elevation. Recreation vessels will like to have this elevated for views. However, it is fine if the boats are still rolling with stiffness. Have a rolling test to determine the rolling period. More professionally, perform an inclining experiment to ascertain the KG and LCG before adding any top side conversion items. For small commercial you should at least have a stability letter. Many stability letters will state the limiting draft, limit of cargo and most important will list the Lightship status (weight, cg positions at x,y,z.). You may be lucky to view a stabilty information booklet, to see tabulated loading conditions or just some curves of limiting KG for various drafts.

    A bench test with numbers should be done in numerically assess the expected modified condition and boat behaviour is essential. A local naval architect can help you to survey the boat and review the stabiltiy before committing in construction work. This is an essential part of the survey. Alternatively, have this work included in their bill of sale for satisfaction of the bidders.

    If the boat is stiff giving large GM and good large angle GZ value with stability range way pass the fishing boat requirements. Then, there may be chance to place a observation tower on top of the existing pilot house. This will require the exhaust pipes to be extended. You may also extend the ex. pilot house aft to accommodate the needed day room. The fish hold can be converted to cabins.

    Conversion cost should be lower in Canada in Newfoundland or in your home state for convenience.

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