Minimum Hp for 48' SD Trawler

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I guess that prompts another question: Being that the boat was powered for more than displacement speed before, what was the top speed with the pair of 225s? And how did it run at higher speeds? That may help determine if it's worth keeping that ability or just powering for hull speed plus a little.
 
She was always 10-12 knot boat. I'd need way more power to get her to the 14-15 knot range. The boat looks exactly like a Hatteras 48 CPMY. Thinking of Hatteras, guess I could find some Detroit 6v53s or 6v71s.
 
From what minimal pictures I can find of the CHB 48 hull, it looks like it should be possible to get it to plane decently, but probably a bit draggy with the big keel, etc. I found some numbers indicating around 12 kts at WOT with a pair of 250hp Volvos. And another boat showing 18 kts at WOT with 375hp Cat 3208s. 50% more power giving 50% more speed indicates to me that somewhere after 12 kts it gets over the drag hump and gets onto some decent kind of plane.

So it would definitely take some power to get it to run any decent speed. But if you were to swap in something like a Cummins B series, other than a bit of extra cost and needing to worry about aftercooler maintenance, I don't see a big downside to putting in a higher powered version that could let it run faster. It shouldn't be any less happy or efficient at low speed than the lower rated versions of the same engine.

Of course, that's all dependent on what engines fit the budget and fit in the available space (and can be gotten in / out of the boat).
 
I don't think two 80hp fords would prevent but a few sales. That boat is simply never practical to run at planing speeds. Any buyer that is looking for that is off their rocker. The market wants good hull speed performance with that hull, and the 80's should do that just fine.

How many of these hulls do you see going down the ditch on plane? Zero, and for good reason. They never did it well, it burned an a$$ of fuel, and was hard as heck on the engines. All the ones still alive run hull speed and buyers are looking for just that.
 
This boat appears to be in the PNW. Here in the PNW we routinely see tidal currents up to 6 kts. While we mostly cruise around hull speed we do enjoy the ability to push it up to 14kts in order to punch through these currents. Ponderosa 48’s have a reputation of being capable of 14 kts. Having a P48 only capable of 8 kts is going to be a bigger turn off then you might expect. That said, it won’t turn off every one.

Problem with the 80’s, who is installing them and how much modification will be necessary? Direct replacement drop ins are usually the cheapest way to go. If the 80’s take a lot of installation modifications you could end up over spending your savings.

Frankly, there is no easy answer to the OP’s question.
 
Ski in NC said:
I don't think two 80hp fords would prevent but a few sales. That boat is simply never practical to run at planing speeds. Any buyer that is looking for that is off their rocker. The market wants good hull speed performance with that hull, and the 80's should do that just fine.

How many of these hulls do you see going down the ditch on plane? Zero, and for good reason. They never did it well, it burned an a$$ of fuel, and was hard as heck on the engines. All the ones still alive run hull speed and buyers are looking for just that.
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:thumb: My views exactly.


David
 
I can't believe I am going to disagree with Brian at A.D. but here goes..

Regarding the stuck engine. Unstick it! It is one of two areas which caused it to stick. The first is rust in the cylinders, not an impossible fix. Pull the head and start looking for rust. hone it and reassemble. The other reason could be a binding of parts, bearings, rods, crank. You might have to lift the engine to inspect but shouldn't have to remove it.

The other engine most certainly has a blown head gasket. Pull the head, have it honed and install a new gasket.

Brian might not have every part for a total rebuild but you really don't need total rebuilds, just repairs. What he doesn't have Bomac might have. Or maybe a farm implement dealer.

I REALY think you can make those engines work. If you are convinced they have to come apart to remove them anyway, you are halfway home.


Unless you can do 90% of the work yourself just pulling the two engines and installing two different engines will cost you a minimum of $7,000. Plus the cost of new engines, even cheap will be $10,000, plus new mounts and perhaps new props, probably another $5,000.
You are pushing $25,000. I know you can repair those two F.L.s for a LOT less.

You don't say what year your boat is but it's doubtful you will come close to recapping your money if you swap engines, especially if you downsize to 90's. It just might become your "forever' boat.

P.S. How are the tanks, don't overlook them while the engines are out or apart.

Good Luck,

pete
 
Another thought - you have a SD hull that will run continuously at about 7knots. The hull will not perform as well as a FD hull designed for that.

That means little in smooth waters, but in rough seas (especially big following seas) it will be a constant battle at the wheel.

Since you likely will dry dock it to reprop, you should seriously consider increasing your rudder area.
 
Ski in NC said:
I don't think two 80hp fords would prevent but a few sales. That boat is simply never practical to run at planing speeds. Any buyer that is looking for that is off their rocker. The market wants good hull speed performance with that hull, and the 80's should do that just fine.

How many of these hulls do you see going down the ditch on plane? Zero, and for good reason. They never did it well, it burned an a$$ of fuel, and was hard as heck on the engines. All the ones still alive run hull speed and buyers are looking for just that.
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I agree fully and as long as you’ve got about 6hp per ton of displacement you should get the stated “6-7 knots” speed.
I think if you research a bit you’ll find comparative information that will confirm that running two 80hp FL’s at 50-60% load you’ll get at least 6 knots continuous speed. If yo find you need to load the engines ar 75% you should abort. Your boat will be at least 1000lbs lighter.

Agree fully w mako you should lengthen the rudders. Or on both edges.
 
I am humbled by your responses and help. All you comments are versions of conversations I have had in my head and some I have not even considered.

As I go back and forth, I think Pete's suggestion may make the most sense.

Anyway you cut it, I'm going to have to remove the engines, be it for less HP, same HP or more HP. (sunk cost estimate $5K)

With the blank slate and an empty ER, what gives the biggest bang for the buck?

1. Replace with reman Cummins (50K engines and transmissions + $50K parts and install labor)
2. Replace with running takeouts (maybe get lucky with a pair of FL 120s) ($25K for pair + $50K parts and install labor)
3. Find a pair of FL120's and rebuild them ($30K full rebuild + $50K parts and install labor)
4. Rebuild/repair the FL 225s (BTW-PO bypassed intercoolers b/c of corrosion so engines are now 180hp - when running:)) ($25K fix +$25K parts and install labor; guessing install labor would be less because no engine bed work)

Options 2 and 3 do not guarantee current Newage/PRM transmissions will work, and props will not need to be tuned to new power.

With option 4 at least I know everything will go back in and mate with current transmissions. I have also built in my parts and labor figure knowing I want to re-route exhaust and re-do current fuel delivery/valving set-up.

Although everything on the boat is new (Garmin electronics suite, bow thruster, electrical, heating, galley, canvas, sanitation system, and the list goes on, ALL done in the past 6 months at a cost of $150K) I'm realistic that even with all the upgrades, it's still a $95-$110K boat.

With all of the above in mind, does it still make sense to keep the boat and rebuild or repower or cut my losses and let it go to someone who may have the skills and time to do the work themselves.

I realize I have hijacked my own conversation so if you think this should be a separate thread, I'll create a new post.

Thanks for your input!
 
It’s one of those 6 one way 1/2 dozen the other way. Will be very hard to sell as is and most buyers will estimate $80,000 to repower and offer you $20,000 or less but maybe some idiot liveaboard wannabe comes along and offers you $50,000. Then maybe you get the engines repaired for $20,000 and sell the boat for $100,000 or the job goes bad and you end up repowering for $80,000 and selling for $90,000. There is no way to know the best direction. You can try selling as is first and then if no offers you can resort to fixing the engines. I don’t think you will find a broker willing to take on your boat in its present condition, hard sale for small commission. Again, there is no easy answer here.
 
Perhaps installing a different brand of engines would make more financial sense?

The International DT 360 or DT466 can be found as running akeouts , usually 5,000 miles for about $3,000 each. Both are inline 6 cylinders.

These are heavy duty engines , not farm implements, usually found in skool buses.

Since the buses are 90% federally funded , no one fixes them after a crash , they just get new ones..

Wet exhaust manifolds are available ( tho expensive) and the bell housing is SAE , so your existing tranny, shaft and prop can be reused.

A pair of $3,000 engines that are very robust sounds better than a huge investment .
 
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FF has a decent idea there, I think. And IIRC, the mechanical injection DT466 came in anything from 190-ish hp up to 270.

But the real question is, even if you don't plan to keep the boat forever, how long do you plan to keep it after getting it running?
 
If it were me, I would fix it regardless of which engine option you choose. If you sell it as is, unless you give it away, the meter keeps running (insurance and dockage or storage). If it took you a year to get rid of it, how many thousands are we talking?

Ted
 
If they are maintained, Bob Smith the Lehman guru before he passed away, told me that the commercial fishermen would bring them in at 20,000 hours for a preventative rebuild. In pleasure boats they aren’t used as regularly and probably not maintained as religiously so less hours but they can easily go 8 to 10,000 hours.
 
Minimum hp

I didn't bother to read any other responses, as the ONLY response is to contact Brian Smith at American Diesel Corp (online).

His dad marinized the Ford to build the Ford Lehman engines.

He'll have all the info you need.

BTW, the info provided on the forum wasn't enough to provide a valid answer.

48' boat that had 225 engines isn't nearly enough.

Good luck.
 
If you are happy with the performance you had before, it is easy to figure out. You do need to know the max fuel consumption that you ever wanted / needed to use with the old engines. That tells you how much horsepower they were putting out. The general formula is gph = 10% of provided horsepower (per engine). (You can probably get some better data specific to your old engines, but 10% is probably on the conservative side.) So if your engines were burning a combined 7 gph, they were putting out a combined 70 horsepower (ie, 10% of 70), or 35 hp per engine. Sounds to me like the 80 hp engines can provide 35 hp all day long with some power to spare.

FWIW, my 660 hp engines burn a combined 5 gph at 7 knots in typical conditions, indicated that my hull requires only 50 hp (ie, 25 per engine) to make 7 knots. My hull length at the waterline is 60', so it is probably a little more efficient that yours.
 
Most diesels will do better than 10hp per gph except maybe at the lightest of loads. Depending on the engine and load, it's usually more in the 15 - 20 hp per gph ballpark (so 5 gph would be 75 - 100 hp).
 
rslifkin said:
Most diesels will do better than 10hp per gph except maybe at the lightest of loads. Depending on the engine and load, it's usually more in the 15 - 20 hp per gph ballpark (so 5 gph would be 75 - 100 hp).
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You are right. 20 makes more sense. I was thinking gas. Sorry.
 
There are mechanics and shops that rebuild almost anything with pistons. Usually in any big city. They have avenues for parts the general public does not. The engines could be stripped, bored in place without ever removing them. The heads go out for rebuilding while the engine is reassembled. You could be done in a week and have a valuable boat with like new engines.
I love Detroits, but I think fitting 6v53s or 471s would cost more.
 
IMHO, needed power at close quarter maneuvering is best made available in the form of bow and stern thruster. As someone pointed out FOT at the slip is unreasonable. I had a MT40 footer with a single Lehman120 an bow and stern thrusters. I never had to rev up the 120 at all.
Without thrusters, this size boats are not safe at the docks.
 
O C Diver said:
For a reference point, my boat is 45', around 45,000 pounds, semi planing hull. Have a single 4045 John Deere 135 HP. I cruise 7 knots at 2 GPH, around 40 HP. 8 knots at 3.5 GPH around 75 HP.

While my engine is pretty good with counter balance shafts, I agree with Ski, the 6 cylinder Lehmans will be a lot smoother than their 4's.

Also, it's very likely if you went with the 4s, that you will need to change transmissions to a taller ratio and will likely need different props. Basically you will need to run at a substantially higher RPM and then reduce the prop RPM through taller transmission gears. Probably nowhere near enough HP 1,200 RPM out of the 4s.

Ted
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can you explain IF the 80's can output 1200 rpm to the current prop and trans that they will not have enough horsepower. That is what I am hearing from several posts. I also hear that the 225's were run at less than 80 HP and not using all potential for their size.

IF 80's are under powered then I do not expect them to turn at 1200 with current trans and props, which then makes sense. Changing gear ratio and prop pitch to allow 1200 rpm would also show underpower by inability to reach 7 knots target.
Of course say goodbye to the 10+ the 225's could provide.
 
Power Up!

Flyguy1967 said:
All,

I just learned that BOTH my Lehmans are shot (long story; wait for the book for all the details).

Current iron are twin Lehman SP 225s. Before both engines cratered, we ran at 1200 rpms which yielded at 6 -7kts. That speed was fine with us.

Have an opportunity to buy a pair of 80hp Lehmans which we could (hopefully) mate with our PRM/Newage transmissions and away we would go.

My question is: do you think we would be TOO underpowered with the 80hp Lehmans?

P.S. - If we were able to make this work, I don't think there would be any questions about fuel economy:)
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My 40 ft. Bluewater Pilothouse Trawler came from the factory in 1978 and the 2 na 120 hp Lehmans have done well. You can get rebuilt ones and parts are available. 80 hp won't work IMHO.
 
rolomart3 said:
Without thrusters, this size boats are not safe at the docks.
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I'd say that's taking it a bit too far. It depends on the boat and windage, but with twins on a fairly high windage 38 footer, I've only had a couple times where I've wished for a bow thruster and none where I truly needed one. It just requires knowing exactly what your boat can and can't do and not putting yourself into a situation where you have to do something you can't.
 
rolomart3 said:
IMHO, needed power at close quarter maneuvering is best made available in the form of bow and stern thruster. As someone pointed out FOT at the slip is unreasonable. I had a MT40 footer with a single Lehman120 an bow and stern thrusters. I never had to rev up the 120 at all.
Without thrusters, this size boats are not safe at the docks.
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Perhaps in this case, the limiting factor is not the boat/equipment, but rather the skill/experience of the operator . . .
 
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