Luhrs T-29 (1995) diesel inboard converted to outboard
This is my second post here.
I am in a middle of a project of converting a 1995 Luhrs T-29 small sportfisherman to outboard power. This may be interesting to those who likes to make such conversion in the future or for knowledge sake.
Since the will be a long post and with many photos, I would first like to get permission from the Moderator and also if other members would like me to continue the post. I am worried that the post will take too much server memory or possibly this sort of subject is of no interest to members.
Please let me know. Thanks in advance.
The 1995 Luhrs T-29 was powered by a twin diesel Marine Power 6.5 liter rated at 275HP/3,600RPM. Shaft & props, not stern drive. Now it is being repowered by a twin suzuki 250HP 4 strokes outboard. The boat is also lenghtened by 5.28feet ( 1.6 meters ). The conversion at this stage is a big success. Let me know if you guys want me to proceed with the details.........
Good question. Since you are from Florida you must have seen a great deal of Luhrs T-29 Open around.
This is a long story. My good buddy bought this boat in 1995 brand new from Luhrs dealer in Singapore. Just from a brochure, never seen the real boat and never test drive one. His budget was limited to this kind of size. He choosen Marine Power diesel instead of gas because of power and realibility and could not go for the Yanmar 315HP because it will cost another US$20k option. It has all electronic options including auto-pilot but no generator. Shipping to Jakarta via Singapore was a killer, it cost US$13K. When it arrived in Jakarta he paid import duty which at that time was a whopping US$25K even though he had help from custom office. So in the end he paid too much for this boat.
The day came when we first sea trial this boat and speed wise it could do 27 knots fully loaded but to our dissapointment the handling was so awful. This boat will keep heeling either left or right above 17 knots, it can't stay stable. It take skill to drive this boat straight. It won't flip over but it is such screw up boat. You need to keep playing with the trim tab, in fact it is better when trim tab sets to zero at the cost of 2 knots lost of speed. In beam or stern sea, this is one dangerous boat. You must really play hard with the steering. In this kind of water, even when set to auto pilot mode, after a while the auto pilot will disengage when the heading error gets too much. What a weird hull. This is one boat when you turn the steering wheel hard to one side in beam sea and it will either not respond or takes forever to make a circle, unless you slow down below planing speed.
Head sea this is a fun boat, soft ride and OK. We have friends who own a Blackfin 29 Combi and Carribean Bertram 28 ( Australian boat with Bertram hull ), that's what we compared this Luhrs against and it is a down right looser.
In fact the Singapore Luhrs dealer who was an Italian guy came to test the boat and he was shocked to witness this sort of handling. If is a far cry from the 35 Luhrs Convertible he sold and have tested extensively. He thought maybe the heavy Marine Power diesel was causing the weird handling problem.
I don't know, this is the only Luhrs in the country and I never test a gas powered one.
Adding to the misery, the Marine Power diesel seems to be over worked at 275HP/3,600 RPM. In less than 100 hours of use and in lesss than a few months, the power dropped and dropped. In the end I have to re-worked the propellers to suit the new lower power. The top speed was way down to 23 knots. As time goes by, the top speed dropped again to 21 knots and that's when my friend stopped using it, we were cruising too slow at 15-17 knots/3,200RPM, depending on load. We made many complaints to Luhrs USA but there is nothing they can do to help with the handling, as it is like that by design.
Engine wise, my friend regretted choosing Marine Power diesel, however that engine is reliable except for the serpentine belt system. In 500 hours of use, the problems been only serpentine belt system ( factory upgraded in 1996 ) where the sea water pump is also linked. Over all the engine never gave problems except the quick power loss over a short period of time. With Jakarta humidty at 80-90% all year round, poor diesel fuel quality, ambient temperature at 30-32 degrees celcius, sea water temp at 29 degrees celcius and engine room temperature at probably 45-50 degrees celcius, I am not suprised to see premature power loss of this crude marinized 6.5 liter Hummer engine.
So after keeping the Luhrs 29 un-used since 1998, this year we decided to do something about it. If we sell the boat, it will be too cheap. The boat except the engine is in good condition. We applied osmosis protection barrier on the hull twice. Once in 1997 and later in 2001. It really works, that epoxy layer made the hull like brand new today.
So, I have two missions for this boat. First is to re-power and second is to improve its handling.
Why we choose gas ?
Diesel fuel price in Indonesia is US$0.18 per liter or US$0.69 per US Gallon.
Gasoline ( lowest octane ) is US$0.20 per liter or US$0.77 per US Gallon.
So price wise diesel and gasoline is about the same. The Luhrs T-29 has the Flo-Scan fuel computer installed and to my suprise its fuel consumption when heavily loaded is totally unbelieveable. The Luhrs owner also own a used Ocean Yacht 53 (1995) which he bought in 1998 with 820HP MAN, which later I install a Flo-Scan fuel computer. There is also another friend with Ocean Yacht 48 ( 1996 ) with 625HP Detroit 6V92TA DDEC with built in fuel computer in the system. I was comparing the fuel consumption for these 3 vessels and it was found out that between low weight loading like 500 liters of fuel and a few persons, the Luhrs was like 0.9 to 0.95 miles per gallon. In highly loaded state and at crusing speed, the Luhrs was sipping fuel like crazy, it was something like 0.60 miles pergallon or worse. I can't remember the detail well but I know the numbers shocked me. On the other hand the 53 Ocean at cruise 31knots/2,100RPM was only sipping something like 0.40 to 0.45 mile per gallon, fully loaded. The Ocean 48 was doing like 0.45 to 0.50, 26knots/2,100RPM.
The Flo-Scan fuel computer was a real eye opener. I love the unit and I really heavily on it because when we cruise, we are far away from proper fuel station.
The lesson I learned, taught me that when one over load a small boat of 11,000 lbs displacement with 1,500 pounds of gear, this is almost 14% of the over all weight of the boat and that can do a lot of performance harm. Not so in a bigger boat with displacement of 36,000 lbs and up. Also the planing angle of the Luhrs T-29 is too high and the trim angle greatly effected by weight on board. Being a short and shaft driven boat, the angle of attack of the shaft is also not efficient. I like the way the Blackfin 29 set up the rudder at the back of the transom ( like a trim tab ) and thus allowing a less angle of the shaft by having a longer overall shaft. The Carribean Bertram 28 is also load sensitive on its performance ( 265HP gas x 2 with shafts ). The Blackfin 29 with 300HP Cat 3116 is not really load sensitive, I wonder why. One thing for sure that Cat 3116 is a real marine engine and have decently good torque.
Using Mercruiser gas inboard as alternative is not an option in Indonesia. The Merc is famous for being a very unreliable engine, especially in the 400HP upwards. Somehow in Indonesia, Mercruiser is short lived. I don't think that is the case in the US. Spare part is also not readily available, the local dealer do not stock anything. Singapore or Malaysia is the closest real supply. Other make of gas inboard engine will not be possible as there are no dealers in Indonesia. Two few friends have 3 of Baja 38 sport model with 415HP fuel injected stern drive Mercruisers among themselves. One have gone thru the original engines and have bought 2 spare ones, still after 3 years all 4 engines were thrown away. This one finally been converted to outboard power with 200HP x 3 conventional two strokes. The hull also get lengthened by 5.28 feet. Now it rides head sea like a dream but steering response a bit slow due to no power steering like the stern drives. Top speed is only 41 knots at 5,500RPM, cruise 32 knots/4,500 RPM, not too bad though for only 600HP of total power .
The other two Baja 38 owned by 1 person, have gone thru extensive repair over and over again untill the owner decided to stop using the boat. All these Mercs have got the fresh water cooling system installed.
The conversion from inboard shaft drive or inboard stern drive to outboards either of diesel or gas, is quite popular here in Jakarta. The main reason in simplicity of repair or engine replacement. If you have the cash in hand, in less than 5 hours you can replace one failed outboard engine with a new one. Try doing that to any inboard engine. Yamaha 2 strokes outboard is very cheap here because they are selling the jurassic version of the smoky caburated model. You can't find these in the US or Europe, they do not pass today's emission regulation of developed nation, let alone EPA 2006 ruling.
The Yamaha 200HP only cost US$6,000 at best. With cheap gas price, it does look like an easy remedy for troubled inboard engines. Boaters also have fear on gasoline inboard, fear of fire and explosion.
Because most engine room of these converted inboards to outboards boats are usually small and cramped, the outboards conversion does look attractive. At the same time, the power conversion also done up together with making the hull longer by 5 feet, all conversion had been a succes in terms of handling and performance. There is one very old 28 footer Caribbean Bertram which was lengthened and modified to use 4 x 200HP 2 strokes Yamaha and it flies to 40 knots. They don't care about the fuel burn, they can afford it.
There is two kind of conversions. One is to cut the hull and make it longer and the other is to extend a new 5 feet hull at the transom. The two conversion I supervised was hull extension at the hull.
The conversion and hull entension for the Luhrs T-29 is because Suzuki in Indonesia has introduced a 250HP 4 strokes recently. I am never a fan of dirty & smoky 2 strokes. It is also the cheapest selling price in the world, because they want to start penetrating the market. Including 10% VAT, I paid US$ 13,500 each. Tie bar, throttle & gear and some gauges options for twin engines is only another US$1,000.
Initially, I have thought of putting 3 x 250HP Suzuki outboards but after some consideration on the poor Kuhrs T-29 hull handling, I decided to use only two. I was afraid the boat will still be "dangerous" to handle above 17 knots. I ordered the new transom and its modification to be for 750HP rating, the same goes for the new outboard steering system. If the modification proves a success, I only need less than US$1,500 to re do the transom to take 3 outboards and buy another 30" 250HP.
The price for the 5 feet hull extension is cheap by US standard, only US$7,000. All fiberglass & resin material is Lyodds approve. The boat yard has been doing this for at least 12 boats if not more. He has developed a reinforcement technique which allows the new hull to stay in shape and made a reliable bonding. Amazing, coming from a boat builder which has no naval architecture back ground. Many of his own designed boats had been succesfuly operated as short haul ferry ( 40 miles run offshore in maximum 6 footer waves, carrying 60 passengers ), running 200HP x 4 outboards. Some of these boats have stood the test of time for the past 10 years.
When the extension job was completed on the Luhrs T-29. I took a look at the new waterline. No diesel engines, no fuel tanks, no batteries and no water tank. It seems the new 5.28 feet hull has good buoyancy, perhaps at least 3,000 pounds extra if not more. At this loading condition, I am getting like 3-4 inch above it original waterline. What was previously the engine room, is not a mid position anymore. I have never liked the way Luhrs T-29 installed its fuel tanks. 150 gallons each on the sides of the engines. Total of 300 gallons. When this boat gets on plane, the engines and fuel is way above water line. It seems the weight concentration is mid length of the boat. Under the cockpit there is a 50 gallons tank right behind the engine room and 2 of 8D batteries somewhere above the propeller shaft brackets. The Blackfin 29 and the Aussie Bertram 28, has fuel tank low under the cockpit. This set up give better stability. I would prefer a planing hull to have its center weight at 40% from the stern.
I am suspecting that aside from a not so good hull design of the Luhrs T-29, it aslo has flaws in the weight placement of objects. I really like the Luhrs
T-29 lay out for diving & fishing but other than that, its handling sucks.
So I ordered a SEA TRIAL 1 condition with totally no load on the vessel, except for a 250 liters of fuel in emergency tank to be located in the middle of the engine room, running aft stern. I took the boat out, it was a choppy 4 footer with confused wave. 6 people on board as trim. I told them all to sit on the cockpit floor. At that time the outboard engine position was set high. I tried planing the boat and by the time it hit 4,000 RPM, the props were cavitating, the props were not biting water. We could not do better than 11 knots and 3,500-4,000 RPM. Slow steering response of outboard, can not be compared to rudders of inboard. Sea Trial 1 was a failure.
SEA TRIAL 2. Next day we lowered the outboard engine two holes down. I also placed weight of 1,760lbs (800kg) below the cockpit floor where I intend to place the new fuel tanks. I used concrete blocks and jerry can filled with water. An emergency jerry can of 100 liters of fuel was placed on the floor hatch of the new extended hull. I took 6 person on board. At this stage the Luhrs does not have a trim tab yet, I will install the original ones later. At 4,800 RPM, I was getting 20 knots and at 5,500 RPM ( WOT ) I was getting 25 knots. The hull now handles beautiful, with confused sea of 3 footers, I was able to make small circles, something not possible before in Luhrs original hull form. I made slalom turns and the boat followed the steering command with ease. Now the boat does not heel sides to side anymore, it tracks straight in beam sea or stern sea. Comes back center line fast too. It also retains its soft ride in head sea. I felt great.
Speed wise it is not too bad either. Running only 250HP x 2 4 strokes and I am getting 25 knots top speed with such loading, this is great result. Now the running angle of the boat is also much better. I think only something like 3-4 degrees at best, instead of the 7-9 degrees with the inboard and original hull. The props tested was the smallest available 16" x 17", I need to raise the engine RPM to 5,800. 5,500 RPM is the lowest allowable WOT by Suzuki. The pattern of usage of this boat will be another 1,000 lbs of people and gear when in maximum load. The water tank will be moved forward to the old engine room and the batteries will be located there too. Even with 1,760 lbs of simulated fuel load under the cockpit floor, I have yet to load the old engine room with 500 lbs of water and 150 pounds of battery. I want the batteries in high area to prevent failure if the boat ever flooded. I could have placed the batteries on the new extended hull but that means it will share atmosphere with the 4 Racor FG900 fuel filters which I plan to install there. Fuel vapor and batteries are not friends. This new hull area is also the most potentially wet part of the boat in bad weather. The new hull has three floor hatches to access fuel filters on both sides and a mid hatch as storage. I am ordering a locking hatch handle and with rubber gaskets, I need to keep this bilge area dry. I also plan to run air hoses to push new clean air into this new extended hull bilge and under the cockpit floor ( new tanks ) for best ventilation.
Next step I need to improve the handling further because it seems 3 of 250HP outboards could be the final destiny for this modified Luhrs T-29, if not now perhaps late next year. I need to test this boat extensively in all sort of weather to really prove its performance at speed. One year of use should allow me to evaluate if it can handle 3 engines which should produce a cruise speed of 27 knots and a top speed of 32 knots or so. So, my next step is to remove any weight on top. The hard top had been a suspect a long time. It stands like 6 feet ( 2 meters ) above water line. Estimated weight of the hardtop fiberglass and its second steering station is about 550lbs (250kg ). I had it removed and sure thing, the fiberglass hardtop alone at such ridiculous thickness weights like 440 lbs. The aluminum railings and second station is light. I wonder why in the world Luhrs would built such a heavy hard top. They could spend a bit more money and use divinycell as coring material, instead of plywood, what a joke.
I have not tested the boat again as they are now doing the new tanks. The cockpit floor will then be of a removeable type to do inspection on the new fuel tanks. Since the cockpit floor is using plywood as coring material, some area has turned rotten. Nothing much but irritating to look at.
The new hardtop will be without the second steering station. Thus I can make it thinner at 11mm. It should weighs only 132lbs (60kg). Nobody will stand there anyway. In fact the original frame supporting it is so robust, it can take one or two adults standing.
My next step is to get improved propellers from Michigan Wheel Ballistic series and order an eletric/hydarulic "Jack Plate" to improve engine trim real time. The new fuel tank will be of only 950 liters (246 US gallon ) capacity, good enough for the boat. If later I can hit top speed of 27 knots at 5,800 RPM full fuel and water plus 4 adults, it will be more than a success. Even with top speed of only 25 knots, by Suzuki fuel flow chart not Flo-Scan reading yet, I am getting 0.9 miles per gallon. Suzuki stated 53 liters (13.77 US gallon ) per hour per engine at WOT. This is hell a lot better than previously achieved with 275HP x 2 diesel in the similiar loading. It looks like it is true because I tested the boat with 100 liters of fuel and got almost 2 hours ( if not more ) out of it at 5,000-5,500 RPM of sea trial. I think the propeller thrust angle, and boat planing angle/trim plays an important role here for efficiency. The original hull with shafts when running looks like it is being pushed upwards moreby the props when planing, instead of forwad......thats hell of a work load. My friend a propulsion expert have told me that if shaft attack angle is above 8 degrees, lots of power lost will be the result. Another friend of mine conducted a test on a 92 feet patrol craft, which topped out at 22 knots. Later they revised the position of the fuel tanks to give the vessel a better running trim, they gained 2 knots. Now the vessel can topped out at 24 knots.
Flo-Scan single display 9000 series with twin engine capability will be installed to monitor fuel consumption. Garmin new 182C GPS/sounder combo with transducer installed inside the hull will be the new GPS. The old baby Raytheon radar still works, the Robertson AP250 old auto pilot I can modified to work for outboards. I have replaced the old VHF with a new Icom IC-M602 DSC capable. I am ordering a custom made sunshade from Atlantic Towers in NJ. My friend does not like stainless steel works, he loves the US made aluminum works.
The fabrication of the 4 fuel tanks ( made of fiberglass ) and new fiberglass only hard top cost US$4,200. It looks like the final cost for the major modification, re-power ( 2 engines ), electronics and etc will run to US$50,000. The current value of a 1995 Luhrs T-29 with Marine Power diesel in the US is probably net at US$50,000 at best, maybe less but with screw up handling.
If you or anyone are interested I will add more report as time progress.
The new extended 5.28 feet hull is not the best of looks but it works.
This is the photo of the boat with extended hull.
be happy IYA! sorry i was speedreading, you had the taxes and other concerns, nice boating!
I like the look, I worked at Luhr's in R&D. I won't ask the money it took and to tell the truth. I don't feel you'll ever be completely happy with your changes. We built it that way for a reason. outboards verses deisel. There is no reason good enough. But it does look good!
Thanks for posting this. Any update on this project? The information on your project was very interesting and informative.
I am looking at converting a 34 ft. Silverton from inboards to twin outboards. I do not care to get this boat on plane - I am considering using 2 x 150hp or less.
Wherever you go, there you are...
Good thing I get email indication that this forum is asking me for a reply.
Use this link for learning how I made the progress on the re-power and extending the hull :
Silveryon and Mainship is part of Luhrs group if I am not wrong.
At 34 feet LOA your displacement hull speed before entering planing speed would be about 6.5 knots.
I know it sounds crazy that you do not need to plane, but 150HP x 2 won't allow you to plane anyway.
I don't want to get into the modification of the transom but if you want least power and do not need to plane, I think 50HP x 2 is enough. It is quite easy to calculate. Put your engines in gear and hit 6.5 knots. Check the RPM you are doing to get that speed. Look at the engine's power chart that tells you at what RPM what HP it is producing.
However, the amount of work you need to remove all underwater gear ( rudders, brackets and so on ) is lots of money and the re-sell value of this boat will collapsed.
I advice you not to do it.
Thanks Iya. I found the post on thehulltruth.com, very interesting and very similar to what I want to do. I think I'll consider putting two 250hp outboards on my 34C Silverton. This boat has about a 5 ft. hi transom - of course it is not structurally strong enough to hold outboards without major reinforcement. You mentioned other boats in your area that were converted. Can you tell me what boats these were - any similar to my Silverton?
Wherever you go, there you are...
I can't remeber all the conversion but I will let you know which one I can remember :
01. Luhrs 29 ( mine ) added 5 feet at transom.
Original inboard 275HP x 2 Marine Power diesel with shaft, +- 28 knots
New Power 3 x 250HP suzuki 4 stroke. +-39 knots
02. Baja 38 ( my friend ) added 5 feet at the transom
Original Mercruiser 415HP x 2 gasoline with sterndrive, +- 50+ knots
New power 3 x 200HP conventional caburated Yamaha 2 stroke, +- 41 knots
03. Cranchi 36 added 5 feet at the transom
Original Volvo Penta 230HP x 2 diesel with duo-prop sterndrive, +- 29 knots
New Power 4 x 200HP Yamaha 4-stroke, 40+ knots
04. Carribean Bertram 28, cut near cockpit and added +- 5 feet in between.
Original 2 x 265HP Mercruiser gasoline in board with shaft, +- 25 knots
New power 4 x 200HP conventional Yamaha 2 stroke 40+ knots
05. Searay 34 ( I think a 34 ), cut near cockpit and added 5 feet in between
Original power 2 x 360HP something Mercruiser gasoline in board with shaft or stren drive I don't remember. Speed definitely not more than 30 knots.
New power 3 x 250HP Suzuki 4 stroke, +- 36 knots. See photo.
06xx. Many other smaller sub 30 footers inboard.
I think the Sea Ray is your closest model to the mainship.
If your Mainship is the same weight like my Luhrs or probably more, make arrangement to finally install 3 of 250HP or wait for the new Suzuki 300HP which should be avalable in the US sometime Febuary 2007 or something like that. Plan well ahead, becareful.
Thanks for all the help. I'll email you as I can't figure out how to view the posted photos.
Wherever you go, there you are...
"Handling: Excellent head-sea boat, dry and smooth. Following sea can be a little tricky...definately have to be on the wheel to counter correct. Somewhat stable at rest but like to "roll" while underway..most likely beacuse of the deep-V and no keel for stability. These boat are SLOW...period. Very few are diesel powered and the majority have gas small block (350cid) Chevy engines (Crusader). Cruise speed light load is about 22mph. You can count on that number dropping with full fuel and you will need it...these boats will drink gas."
Last edited by charmc : 03-07-2007 at 01:46 PM. Reason: added source for quoted review
Here's another report on handling:
"I am a Luhrs fan but I can attest first hand that the 29 Luhrs handles terribly. I didn't think it was scary, just incredibly annoying because it wants to ride on one side of the hull or another but never upright for more than a few minutes. No one can move a muscle while underway or it throws the whole boat off. Head sea ride was really good...if the hull wasn't riding on a chine when you hit the wave."
Obviously, IYA's conversion and hull modification is major work, not to be undertaken lightly. He demonstrates a good knowledge of how to analyze performance and handling, however, and the conversion and hull extension are based on similar work performed - and proven on other applications. I like it.
It's the lifting strakes nearest the keel/stern
Guys here in Tx had the same problem, and removed the lifting strakes near the stern and all of a sudden they had a whole new boat. Softer, more stable ride. Something they'd been unable to do with even the biggest trim tabs.
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