Twin to Single conversion- Oh My!

Opening a can of worms here.

******* Lets say a friend of mine (okay me)* buys a quality trawler in the 42' to 48' range.

The boat is cheap but mechanically a nightmare.* The engines are not taken care of, rusty, oily, smokey.

The engine room is a tangle of wires and hoses everything is old and on its last legs.


To make matters worse one prop is bent the shaft suspect and a rudder cracked.


Okay you get the picture the boat is a project.


********* What if I gutted the engine room and started fresh. Everything new.

**********Dump the old engines and put a brand new modern engine on centerline

********** with new drive train and centerline rudder.

********* Even redo as new the instrument panel with a single engine layout.

********* Throw in a bow thruster for good measure.


Here is the question- I know it would be a fun project and take a lot of time and $$$



But would the boat be harder or easier to sell, compared to simular twin engine models with decent engines?

Basically I am asking is the boat being ruined or improved?

Seems supply is limitless in this size for twins and very few singles can be found.

I assume the boat with one modern engine would be more economical to run and maintain.

Okay let me have it.

JohnP

This is not positive, sorry i am not wishing to sport with your feelings.
There is a Grandma *saying that goes like this :-


"You cant make a silk purse out of a pigs ear "


Donald & Mavis

OK, the first thing you need to know is that I am a total devotee to single engine boats. The second thing you need to know is that most people appear not to have my love for singles. There are many valid reasons for each, and I see no need to go into that. THE REAL THING YOU NEED TO KNOW IS THAT MOST, IF NOT ALL TWIN ENGINE DEVOTEES WOULD NEVER CONSIDER A SINGLE ENGINE BOAT, BUT MANY OF US SINGLE ENGINE LOVERS WOULD CONSIDER THE RIGHT TWIN ENGINE BOAT.

Now that we have that out of the way, let's approach it differently. If YOUR FRIEND* acquired the hypothetical boat for near nothing, and the interior and exterior were in decent shape, I would price out the whole engine swap and make the decision only on your own desire to own a single. There are many designs out there that you could only get in single by doing just as you suggest.


Final thought. Having replaced the engine in my single many years ago, I can say that you would very likely spend in the neighborhood of the same amount of money either way. Just from the investment side of it, I would leave it twins. If however you are convinced this will be a twenty year relationship with this boat, then do it the way you want.

*



-- Edited by Carey on Saturday 26th of February 2011 05:50:53 PM

SOMERS wrote:

*
"You cant make a silk purse out of a pigs ear "






What if the boat were beautiful to start with?* Like a Grandbanks or Defever or?



I like working on boats.

I don't want to go fast.

I want*to minimise my carbon footprint.

I like enormous engine rooms.

I do agree just buying a single is probably the best way.

Click to expand...

JohnP

*


-- Edited by JohnP on Saturday 26th of February 2011 06:58:29 PM

-- Edited by JohnP on Saturday 26th of February 2011 07:06:15 PM

To me, I just don't see the effort being worth it. Two small engines for a repower, IMO,would be cheaper to install than to completely throw that kind of time and effort into basically reinventing the wheel. Sure, it CAN be done, but in this market, I don't see it being the right move.

Tom-

-- Edited by GonzoF1 on Saturday 26th of February 2011 07:19:03 PM

The boat housed across us at our marina is a Californian trawler originally powered with twin Perkins. The owner had them replaced with a Yanmar single engine utilizing the twin shafts and props. The following is a link the website of the yard that performed the swap with before and after photos:www.philbrooks.com/YardServices/GearedUpSystems.aspx




-- Edited by rochepoint on Saturday 26th of February 2011 09:53:41 PM

as a broker I can tell you that more people will want a twin screw instead of a single screw. I can also tell you more people want a sea ray than an old diesel trawler. But yes- you have a larger resale audience with a twin screw configuration. I personally think it is mostly a matter of experience and perception but that is another discussion. I would agree though that repowering with 2 very small diesels to get to hull speed would probably be less money than twin to single conversion. But like Cary, I am very much becoming a single engine devotee!

Mike wrote:

"You can't make a silk purse out of a pigs ear "

Donald & Mavis

Click to expand...

Of course you can. All it takes is a sufficient application of money, time, and desire.

I agree with the economics as described by Carey.* His analysis is spot on.

I have done it - not on my own boat, but for a customer.

When the customer approached me he had already selected his engine, and discussed the change with the designer of the boat - Arthur DeFever.

Mr DeFever suggested where and how much ballast to add, and provided drawings for a new centerline rudder.

With* that info in hand it was a pretty straight forward job.

Mike
Merritt Island, FL.

Click to expand...

Mike tell me more, which Defever? I'm considering this for my Defever 48. The keel is obviously molded for a single engine option. Art must have considered this on my boat.

*

I don't know about over in the USof A but here in Aus. Singles are very much in demand mainly by people who are experienced boaters, those who have been brought up on boats or in the fishing industry etc.
The twin engine thing is basically new and endeared by those who do not have the boating background.
The go fast era is still with us in some ways but not embraced by those who appreciate cruising longer distances.

I don't think I would take on a project of converting a twin to a single, I would just install a couple of nice little diesels sell the boat and look for a
good single engine hull to do up.
I like my projects but that conversion would be a bit much for me.
Even if the interior was really good, it would still have to be gutted to some degree to do the replacements either single or twin.

Now you can all shoot me.

Benn

I think this project could turn from fun to nightmare VERY quickly. There is no real way to estimate the scope of the job. At the end of the day you will still end up with a "Bastardized" boat. The twin screw people don't want it and the single screw folks will be very suspect. Boat yards are littered with good intentioned projects that can be had for 10 cents on the dollar.

I am a confirmed believer in do it your self projects ,customizations and conversions. Having said that it has to make some type of economic sense. These are fun but costs can spiral out of control fast. If you are doing it to see if it can be done, then fine it is an ego project-and acknowledge such and go for it! If your intent is to "flip" and make some bank, forget it. You can do better IMHO.

Would make far more sense to re install twins , but this time use engineering , not the sales office to decide what to install.

I would use International DT 360 or 466 if you want to keep the mush boat , semi plaining option.

Much smaller Kubota if 8K cruise is OK.

With a Twin Disc (instead of a fork lift takeout ) tranny the boat would be reliable.

The hassle is this was not a pure displacement hull, so will always suffer from higher fuel burn at slow speeds.

I thought long and hard about converting a twin engine 40 ft Mainship Pilot into a single.
I had a good plan, and I didn't think it would have been all that difficult.
If we could have found a suitable candidate I would have done it.
Initially I planned on using the best of the existing engines. Then after a couple of years do a repower with the "right" engine. Probably would have been a C series Cummins.

Thanks for all the replys.

******* I do not really plan on doing this.* I just wanted to get the general opinion.

In fact I have done this successfully in the past on a small scale.* I converted a 30' Owens wood cruiser from 2 small block chevys with direct drives to a single big block with 1.5 to 1 gears.

The boat was quieter more economical and actually top speed was unchanged.

******* There were tons of twin screw trawlers built in the hay days back in the 70s and 80s.** It is possible there could be a huge glut on the market as these boats age.
The little guy $$$ is being squeezed out of boating and the big guy $$$ will want something newer than these 30+ year old boats.

******* As these boats sit on the market and deteriorate their value will plummet.

I love to bring* old boats back to life, but I agree the costs would never be recouped.

We like our present IG32 single but if I were younger I think I could consider a project boat.

JohnP

Ah, the eternal Trawler Forum debate.

A question for Daddyo - The DeFever 48* performs admirably with twins, yielding about 4 - 4.5*gph at cruise. There would be little if any fuel savings in converting this nearly 30 ton vessel to a single. It would not handle any better, in fact worse around the docks. The current twin props*are well protected*by the deeper keel. The engine room would not benefit as the two now off center easily accessible engines would be modified to one in the center thus clogging up the deeper center line access. Cost to do it right would easily be $100K and figure another bunch of $$ to add a thruster.* Art DeFever considered this one of his best designed vessels, as well he should, over 170 were made during its 20 +*year production run.*

If you are considering a boat with a hollow keel that was offered as a single or twin, the conversion isn't that difficult. As vessels get larger it's more common to see twins instead of a single. But if you converted a boat like a twin engined Kadey Krogen 42' to a single, I don't think anyone would blink. I have looked on and off at a 38' Taiwan boat with twin Lehmans that was also sold with a single, and thought it a pretty straight forward conversion to a single as it has the hollow keel for a single engine setup. Numbers vary as to the fuel savings, but there is likely 15 to 20%. As to maneuverability, a big rudder makes a huge difference. The one I built for my boat is almost twice the surface area of the original and makes a huge difference when docking. Then of course you could also add a bow thruster.

Ted

What If?

Take the two engines out as suggested, gut the ER of everything....

Increase the size of the GenSet to power*two new electric DC motors.....

and of course I prefer Galley Down.

El Sea wrote:

What If?

Take the two engines out as suggested, gut the ER of everything....

Increase the size of the GenSet to power*two new electric DC motors.....

and of course I prefer Galley Down.

Click to expand...

********* This is something that would be interesting-**

**********How about hydraulic motors driven off a single?

********* JohnP

*

Take the two engines out as suggested, gut the ER of everything....

Increase the size of the GenSet to power two new electric DC motors.....


Then the hobby will be needless spending huge piles of cash , not boating.

I agree with Jack and Fred on this one.

A project like this will be very hard to plan ACCURATELY. Your $$ estimate of the completed project will be very soft, leaving you committed once you pass about the 40% point. Your committment intensifies as you spend more money on it.
Then when you are hit with the unexpected, you may have to rob your Aunt Tillie to complete it.

And will you ever actually get out on the water? Well the longer you take to complete this project, the more money it will cost since all the cost elements will increase in cost over time.

Your present boating life would be over.

Find the best boat you like that best meets your current requirements (as Fred calls them - DESIREMENTS) and move on to real boating.

As much as I really do like working on projects on my boat (and I always have something going on) there is nothing I like more than actually running the boat !

R.

Just repower it w engines half the size of the originals. Many of the engines in the 55 to 65 hp range are naturally aspirated and the total power would be the same. In that size range (like Tony says) most buyers are going to want twins. The vastly better maneuverability afforded by twins is much more important w a boat of that size. In that size range I'd recommend twin screw and thrusters at both ends. This plan would provide the greatest in maneuverability and economy. There was a GB 36 that has had it's 2 120 hp Lehmans removed and 2 55hp Yanmars installed. The boat (I think) produced was considerably more economical to run and more seaworthy as well.

nomadwilly wrote:*There was a GB 36 that has had it's 2 120 hp Lehmans removed and 2 55hp Yanmars installed. The boat (I think) produced was considerably more economical to run and more seaworthy as well.

Click to expand...

********* Can't wait to hear what Marin says about the "more seaworthy" part.

JohnP

It's simple John. Take a ton or so out of a big old heavy boat and it will go faster, run drier and not bury it's bow so much, be smoother, *be more economical, probably make less noise and be less likely to broach. The engines will be much less obnoxious and Marin won't like that. Two D8 Cat engines would make him much happier.

Eric,** What about the Center of Gravity?* Without the ballast of all that iron the boat would be lighter and float higher.

Adding ballast would defeat the purpose.

So the higher CG would be no problem?

JohnP

John,
I now have a response from one of the best NAs on the forum.
However he's not too egar to stick his neck out too far as I was unable to be specific enough. Also he made reference to "the main deck" and I for one was not sure what he meant. Anyway he said that the vertical CG (VCG) is on most"modern motoryachts" is approximately 1/2 WL to main deck height. He claims that to be quite vague and general as there are so many variables but none the less that's much higher than I had thought unless the "main deck" is the same as the salon, after decks and aft deck. In the GB example the engines on the twin are 6" higher than the single but VCG is close to only 1" different. All of this seems odd to me but let's see what he says about where the main deck is.***** Later


His next post showed the CG to be about 12" above the WL. Still higher than I thought. Now
I like my 2 tons of ballast even more.......and no FB. ha ha


-- Edited by nomadwilly on Sunday 6th of March 2011 09:24:09 PM

Eric,
Are you sure you don't really long for a twin screw, flybridge boat with 1,500 horsepower burning 75 GPH??? Just think how fast you could zip around Thorne Bay and the view you would have from up high on the bridge!

Woodsong wrote:

Eric,
Are you sure you don't really long for a twin screw, flybridge boat with 1,500 horsepower burning 75 GPH??? Just think how fast you could zip around Thorne Bay and the view you would have from up high on the bridge!

Click to expand...

TonyYour ability to read between the lines and discover the true Eric, the Eric that Eric didn't know was there, is amazing. I imagine Eric breaking a tear right now, as he realizes that what you say is true.*

*

nomadwilly wrote:
I like my 2 tons of ballast even more.......and no FB. ha ha

Click to expand...

**********Eric, Seems like boats can be pretty forgiving as to the weight and #of engines.

********* On a smaller boat the FB is a lot of free realestate, and does not have to be heavy.

********* If conditions are bad it is easy to stay off the bridge and keep all the crew weight low.

********* On big boats the bridges have tons of furniture, outdoor kitchens and 8 person hot tubs.*

********* But they can always lose the helicopter if things get rough and take a trip to the mall or something. ha ha.

JohnP

Carey wrote:

*
Tony

Click to expand...

Your ability to read between the lines and discover the true Eric, the Eric that Eric didn't know was there, is amazing. I imagine Eric breaking a tear right now, as he realizes that what you say is true.*

*


*



Caery,

They don't call me the "Dr. Phil" of boating for nothing! *

Nail on the head Carey but I just can't afford it. I'd have a 53' Krogen Express. Or a 31' Bertram w twin 375hp. Or a Shannon SRD 38. Or a Mainship Pilot 34. Or a Sterling Atlantic 43. Or an Eagle 40. But the one I really want is a slow boat***** ...Nordhavn 46.

John,
The FB real estate is NOT free. One pays the price of higher CG and windage. Do you really think a typical FB is light? My anti-FB stand is not as bad as most of you think. I DO think most FBs on a 26 or 28' boat is bad design but on a 36' typical trawler it's more of a preference to me. A boats purity of design is more important to me than most. I'll never say a GB is more seaworthy with it's FB than without it though. But if I had a 42 GB I'd not remove the FB.

-- Edited by nomadwilly on Monday 7th of March 2011 10:23:52 AM

But if I had a 42 GB I'd not remove the FB.


Depending on how the boat was built it might be self removing.

I had to create a cored roof for a 42 Californian , as the mounts for the FB , deck boxes and seats , leaked into a ply "composite" .

Screw removal was not required to strip the old stuff off.