Engines for my 42' Hatteras LRC

[PierreR]

PierreR is almost right .. but not.

One dosn't make a FD hull on a boat by cruising it a FD speeds.
A FD hull is a boat w the hull-form of a FD boat. It is 100% a matter of hull form. And most notably the quarter beam buttock line is the part of the question that most directly identifies the FD hullform. WO getting real technical the QBBL is the angle of the hull bottom as it rises (as one goes aft) from about amidships. This angle limits the fwd speed. The aft section/stern going over hull speed will pull the stern down and hence raise the bow.

All of this has nothing to do how fast a skipper runs his boat. It’s the hullform.

Kinda figured someone would call out for more information. The hull bottom as you refer to going aft is called aft buttock lines.
The Hatteras 42 LRC is a shallow draft boat (thank god) and depends on beam length to beam ratio to achieve that. That beam is carried well aft to give a lot of buoyancy to the stern. The wide stern is to control fore/aft pitch, allow for highly variable fuel loads and to allow for higher speeds than full displacement.
None the less, the aft buttock lines are fairly flat but not really enough to allow for a lot of lift. The chines are sharp at the transom and no part of the transom is above the water line at rest.
As you say, the hull form cannot be fooled even if the engines are overpowered. That is true and the handling characteristics of the 42 LRC prove to me beyond a shadow of a doubt that the hull form is semi displacement. A true displacement hull will start to wallow and hunt when driven above S/L ratios above 1.4. The 42 LRC still handles fine and begins to lift the bow. The stern wave you can surf on at 10 knots. The D/L ratio for this 42' boat is about 300. Given the length beam ratio of less than 3:1, this is consistent with the line drawings.
Now if you want to define full displacement by some other measure, that is up to you. I will stick with David Gerr and his teachings at Westlawn.
I have no problem with anyone believing that the Hatteras 42 LRC is a full displacement yacht. I am under no such illusion however, even I start to change the lines and power figures in my head more towards full displacement when I have not recently reviewed and calculated the lines. 30 Years ago, I decided on the Hatteras 42 LRC as a future boat. I happen to like the compromises Hargrave chose. The only difference from then to now is I prefer the MrkI menopause arrangement in the aft stateroom to the pre menopause setup for the Mrk II. Funny how age changes the preferences.

 

[PierreR]

nothing wrong with a semi displacement boat at all I’m actueally quite fond of them but my Willard 36 pilothouse no matter the power isn’t getting much faster than hull speed. My Willard 36 also weighs more than a hatteras 42lrc and the Willard has I believe around 7,000 lbs added just in ballast. Also I just repowered my Willard and went with the stock engine and absolutely overpowered the boat, wish I went with about an 80hp diesel instead of a 120hp. All my extra power gets me about .5 kts over hull speed which only takes about 40hp to get to hull speed so absolutely a waste, with the engines in the hatteras 42lrc she is doing 2.5kts over hull speed. Doesn’t sound like much but it is enough to look at and say hey that’s a little too much speed for a full displacement boat and I bet with a little more power she would be even faster.

My 42 LRC weight over 41,000 lbs in the slings. Your 36 weights more than that? I have specs on the 40 listed as 33,000 lbs. Dry weight on the LRC is 36,000.

 

[PierreR]

I am open to anyone trying to screw with my head and convince me that I own a full displacement trawler. I would love to have my head in the sand sometimes.

 

[garbler]

Maybe I am making too many assumptions in this thread without knowing exactly how Muriel is going to use the boat. My assumptions have been concern for high gas prices and running a lot of canals with 6 mph speed limits. Maybe I am wrong, and the bulk of his cruising will be in the Med with time schedules to worry about.
In the canals, I would not want the DD's as the exhaust is loud. The DD's are back pressure sensitive and require higher rpms before the issue diminishes. To account for this the exhaust exits are above the water line until the boat reaches about 6.5 knots. I would not want to be in a mile long tunnel at 4 mph with DD's. On the plus side, no one would enter the tunnel as you could hear the DD's a half mile away at the end of the tunnel.
If canals and fuel price is the concern, repower a bit lower than the 112 Hp Detroits. If he wants to run fast much of the time then the Duty rated DD's and the JD's are the way to go. DD's like 70% power, right around 1,800 to 1,900 rpm and 8.5 knots.

Back pressure can be an issue with smaller two cycles but from years of experience DD’s normally don’t suffer from this with properly designed exhaust runs. Not sure what you consider ” higher RPM’s “ but Detroit two cycles do quite well on the left side of your tach. Restrict them or design them with exhaust lines too small, restrictive mufflers or exhaust ports too low and numerous elbows that can restrict flow and yes it’s a problem. But I’ve worked lots of marine construction jobs where 53 and 71 series Detroits run most of the day at 12-1400 rpm’s without any problems. Four cycles can coke up ( build carbon ) at low RPM’s but most Detroits don’t seem to. Back pressure and occasional back flooding and hydro-locking an engine is a real concern with sport fishing boats where stern-to the fish fight is necessary. Even then it usually only occurs with swells and sea hitting the transom

Rick

 

[PierreR]

Back pressure can be an issue with smaller two cycles but from years of experience DD’s normally don’t suffer from this with properly designed exhaust runs. Not sure what you consider ” higher RPM’s “ but Detroit two cycles do quite well on the left side of your tach. Restrict them or design them with exhaust lines too small, restrictive mufflers or exhaust ports too low and numerous elbows that can restrict flow and yes it’s a problem. But I’ve worked lots of marine construction jobs where 53 and 71 series Detroits run most of the day at 12-1400 rpm’s without any problems. Four cycles can coke up ( build carbon ) at low RPM’s but most Detroits don’t seem to. Back pressure and occasional back flooding and hydro-locking an engine is a real concern with sport fishing boats where stern-to the fish fight is necessary. Even then it usually only occurs with swells and sea hitting the transom

Rick

By 1,200 rpm, my exhausts are covered with water. At idle they are not.

 

[garbler]

By 1,200 rpm, my exhausts are covered with water. At idle they are not.

Understand. If the exhaust ports are big enough they shouldn’t be submerged at that RPM to my thinking. They should be big enough to allow good flow with still lots of air space. I’ve had my head over the stern on lots of sportfishers at different speeds during sea trials and as best I can recall exhaust ports were still pretty much dry from both exhaust pressure and hull wash which keeps water away from them. On most of the commercial boats I’m familiar with the ports are in the neighborhood of 6-8” diameter for smaller Detroits and larger for larger models and well above the waterline. It could be a trim issue, a characteristic of low speed operation or exhaust port elevation but I’m just guessing. I can’t imagine Hatteras not having this all figured out correctly. Anyway this is interesting.

Rick

 

[Variemeh]

I will happily agree that she is somewhat in between full displacement and semi as you previously mentioned as she wallows along very much like a 1970's sailboat at times.

 

[PierreR]

Understand. If the exhaust ports are big enough they shouldn’t be submerged at that RPM to my thinking. They should be big enough to allow good flow with still lots of air space. I’ve had my head over the stern on lots of sportfishers at different speeds during sea trials and as best I can recall exhaust ports were still pretty much dry from both exhaust pressure and hull wash which keeps water away from them. On most of the commercial boats I’m familiar with the ports are in the neighborhood of 6-8” diameter for smaller Detroits and larger for larger models and well above the waterline. It could be a trim issue, a characteristic of low speed operation or exhaust port elevation but I’m just guessing. I can’t imagine Hatteras not having this all figured out correctly. Anyway this is interesting.

Rick

Now you have got me to thinking and I will have to check and really observe the boat the next time I take it out. I know the exhaust ports are not 6' in diameter and the bottom touches the water at rest. The stern wave does not break from the hull at the speeds I have been going and the exhaust is quiet. I might be making more assumptions here based on that. I know its loud at rest and idle but much quieter at 6-8 knots.
To me, the noise is quite acceptable in the cabin and fairly quiet on the fly bridge at 6-8 knots. I have been running the boat around 1,400 to 1,600 rpm most of the time. I need to take a peek right over the stern and see what is going on.

 

[rslifkin]

Water flow around the exhaust ports aside, some exhaust setups are quieter and louder at different RPMs depending on how things in the system resonate. My exhausts get noticeably louder at 1300 RPM compared to 1200 for example, but 1300 to 1400 hardly makes a difference. The difference is a change in resonance that adds a bit of drone.

 

[garbler]

I know for a fact that spun fiberglass exhaust piping resonates. It may not be louder but it has a special tone that some sport fishermen think alerts fish. Rubber exhaust hose is certainly quieter but years ago all we had was Carlisle hose with spring steel encapsulated ribbing that eventually broke through the walls from corrosion. I’ve seen a number of boats with sections of glass tube then hose then tube and hose to the ports. Somebody thought this out but it wasn’t me. Went to a lot of work so there may be some acoustic advantage ?

Rick

 

[PierreR]

I know for a fact that spun fiberglass exhaust piping resonates. It may not be louder but it has a special tone that some sport fishermen think alerts fish.

Rick

Gotta laugh at that one. Some men also think that loud throaty pick-me-up trucks also attract women, but I have not witnessed any evidence of that.

 

[rslifkin]

I think a lot of it comes down to glass tube being more durable.

 

[garbler]

Gotta laugh at that one. Some men also think that loud throaty pick-me-up trucks also attract women, but I have not witnessed any evidence of that.

I know it sounds crazy and I’m laughing but I have to tell you there are real hard core sport fishing boats and skippers who believe things like engine and exhaust noise, some propellers, bait pump noise, etc. that broadcast sound waves that theoretically spook fish. It even goes so far as comparing wooden hulls vs fiberglass vs aluminum hulls and how they fish. So there are lots of schools of thought based more on fishing success than submarine acoustics. If you ever get a chance go to Bimini or Walker Cay and set down at the bar and listen. It will boggle your mind.

Rick

 

[mvweebles]

......My Willard 36 also weighs more than a hatteras 42lrc and the Willard has I believe around 7,000 lbs added just in ballast. Also I just repowered my Willard and went with the stock engine and absolutely overpowered the boat, wish I went with about an 80hp diesel instead of a 120hp.

The Willard 36's were spec'd at 25k lbs, but the few I know of that have been weighed come in at around 32k lbs, including mine. Always hard to tell how much is design-weight, how much is owner-bloat They were also spec'd with 6000 lbs ballast, the W40s were increased to 7000 lbs. But I suspect these were highly variable - no one likely knew how much ballast was going in. The W36 is a low, deep boat with a very favorable A/B ratio.

W36's were produced from 1961 through 1970, a total of 39 hulls (mine was the last one). Engine selection was not standardized until fairly late in the run. Some had International Diesels, a couple with DDs, a FL120 or two, and at least one Grey Marine 180hp. But to the extent there was a base/stock engine, it was the Perkins 4.236 75hp engine; with an upgrade to a 6.354 135hp. Many owners chose the upgrade "bigger is better" engine which was a mistake - the Willard full-keel displacement hull won't exceed 8-1/2 kts with a pair of Pratt & Whitney's bolted to her deck. In 1987, A W36 with Perkins 4.236 went from SoCal to Hawaii, 2300 nms, and burned 335 gals of diesel, roughly 0.9 gph and averaged 6-kts.

Peter

 

[Jmarsh203]

My 42 LRC weight over 41,000 lbs in the slings. Your 36 weights more than that? I have specs on the 40 listed as 33,000 lbs. Dry weight on the LRC is 36,000.

Could have swore I saw that the 42 lrc weighed 28,000 lbs and some change dry. Looked it up and only saw it in 2 places so that could very well be a miss type from some brochure, my Willard weighs 33,000 dry, And close to 40 wet.

 

[Jmarsh203]

The Willard 36's were spec'd at 25k lbs, but the few I know of that have been weighed come in at around 32k lbs, including mine. Always hard to tell how much is design-weight, how much is owner-bloat They were also spec'd with 6000 lbs ballast, the W40s were increased to 7000 lbs. But I suspect these were highly variable - no one likely knew how much ballast was going in. The W36 is a low, deep boat with a very favorable A/B ratio.

W36's were produced from 1961 through 1970, a total of 39 hulls (mine was the last one). Engine selection was not standardized until fairly late in the run. Some had International Diesels, a couple with DDs, a FL120 or two, and at least one Grey Marine 180hp. But to the extent there was a base/stock engine, it was the Perkins 4.236 75hp engine; with an upgrade to a 6.354 135hp. Many owners chose the upgrade "bigger is better" engine which was a mistake - the Willard full-keel displacement hull won't exceed 8-1/2 kts with a pair of Pratt & Whitney's bolted to her deck. In 1987, A W36 with Perkins 4.236 went from SoCal to Hawaii, 2300 nms, and burned 335 gals of diesel, roughly 0.9 gph and averaged 6-kts.

Peter

Love the Willard, I’ve got trident. rides so well for a 36 footer. I’ve got a 36 pilothouse model with a 6.354 and really wish when I did the repower I put In a 4.236 or a naturally aspirated JD 4045, such a better fit for the boat, the upper 1000 rpm does virtually nothing. She just came out on the slings and weighed 38,500 lbs. that’s with half full tanks and owner things for living in.

 

[mvweebles]

Love the Willard, I’ve got trident. rides so well for a 36 footer. I’ve got a 36 pilothouse model with a 6.354 and really wish when I did the repower I put In a 4.236 or a naturally aspirated JD 4045, such a better fit for the boat, the upper 1000 rpm does virtually nothing. She just came out on the slings and weighed 38,500 lbs. that’s with half full tanks and owner things for living in.

Trident is Forest Myers old boat. She was well kept until she sustained some hurricane damage 10 years ago or so.

In the foreground is Trident, circa 2006, with another W36 PH "Dusty Rose" in the background.

Peter

 

[Muriel 42LRC322]

Repowering my LRC 42'

Dear All,

Thank you again...

I may end by changing for OR the JD 4045TFM50 (mechanical engine) OR the Cummins 6B (no turbo) of 120hp rebuilt.
I have a better price for the cummins of course... less guarantee also (one against 2 years of course for the new engines).
I still have to check if it would go through my 24" clearance door like the JD.
Beta is hard to negotiate and I have been told about a bad mix between aluminium and steel...

That's where I am waiting for my final quotations....
I will re do my DDs then and resale them after !

I will have to change at least one gear box.

 

[Xlantic]

Muriel, are you buying new engine sensors/senders and instruments or do you plan to re-use the current ones?

 

[Muriel 42LRC322]

Instruments

If I go to for the 6bs... I have no choice than having new panels compliant with the Cummins... No ?
Thank you G....

 

[Crux]

Sounds like a good plan coming together!

I would suggest.....go ahead and replace the second transmission now, so you have a new matched set, and don't have to come back 're-lick' this calf of engine room work.

Then, let both transmissions go with the 4-53's.... bolted back togeter,
selling as a complete matched set.

Have you checked into the condition of the fuel tanks??

 

[Muriel 42LRC322]

I understand your point for the transmission and I agree. My final bill is just growing and growing.... but it is right.... and then fuek is the next step... to clean the current gasoil... and the tanks as much a possible but it is not an easy mission. Then cleaning and repaint of the engine room... then the new engines.

 

[Crux]

Cost wise, on the scale of the work you're doing, the cost of one transmission on its own, may not move the needle very much.

Here's a good place to review transmission specs and prices https://www.michiganmotorz.com/products/marine-transmissions
(no affiliation)

 

[Jmarsh203]

Dear All,

Thank you again...

I may end by changing for OR the JD 4045TFM50 (mechanical engine) OR the Cummins 6B (no turbo) of 120hp rebuilt.
I have a better price for the cummins of course... less guarantee also (one against 2 years of course for the new engines).
I still have to check if it would go through my 24" clearance door like the JD.
Beta is hard to negotiate and I have been told about a bad mix between aluminium and steel...

That's where I am waiting for my final quotations....
I will re do my DDs then and resale them after !

I will have to change at least one gear box.

I’m a fan of the Cummins 6b only has minor issues make sure killer dowel pin issue is resolved before install if you go that route and every 10-15000 hours I see front and rear main seal issues which if you don’t care about a little oil is very manageable, we consistently put off those leaks 3-5,000 hours once we do see them so not a big deal, nothing an oil pad won’t solve for prolonged usage. Cummins should easily be a 25-30,000 hour motor without turbo, the jd4045 will be slightly more efficient and has replaceable wet liners so it can be rebuilt indefinitly. Also JD will hold value better over long term and I’d be suprised if they didn’t easily break the 40,000hour mark with proper care. Either way I think if you are doing a swap those two are a great route and can’t think of better engines for the boat.

 

[Jmarsh203]

Once your all done with the swap if you don’t mind posting the price, I’m looking at 6bt or 4045 swap on my twin engine alloy boat as well.

 

[Insequent]

Muriel

I think you are basically on the right track with either JD or Cummins, and selling the 4-53's incl. transmissions to someone elswe. But another option that might be worth considering is Nanni John Deere? There are people in my part of the world that say Nanni do a better job of marinising a JD block than JD do themselves. Witness that its common for JD marine diesels to have aftermarket exhaust elbows and oil coolers, amongst other things.

One issue for you though is that the smallest 4045 block from Nanni is 150hp (their N5.150) and it is common rail but mechanically controlled (whatever that all means!). Which might lead you to consider the Nanni N4.115. It uses a Kubota block, which I would think is fine given the number of Kubota's in industrial machines.

Nanni also marinise Toyota, Scania & MAN engines at higher HP levels, in addition to John Deere. I have no affiliation but sense that they know what they are doing when it comes to marinisation.

As a bonus you should get a user manual in your native language, as well as good local support!

 

[Jeff F]

I may end by changing for OR the JD 4045TFM50 (mechanical engine) OR the Cummins 6B (no turbo) of 120hp rebuilt.

I have a better price for the cummins of course... less guarantee also (one against 2 years of course for the new engines).

The 6b would be a reconditioned unit sold by Cummins, correct?

I'm surprised that Deere still offers the 4045TFM50 as a new motor. I have the more modern 4045TFM75 and it was new in 2005.

Both fine motors. I think I'd choose the Cummins, all else being equal. The factory recon motors are as good as new, from all I've read.

 

[Mainecoast]

How many thousands of hours on those motors everyone replaced? Tens of thousands?

 

[Crux]

A word on transmissions....avoid the Borg Warner 5000a at all costs....Hurth is fine.

Do I understand correctly, that you're thinking of having the 4-53's overhauled before selling them?

 

[Muriel 42LRC322]

My 4-53 are supposed to be 1600 hrs approximately which is nothing... the boat spent before I purchased in 2019 3 years for sure without cruising... for good reasons from the previous owner. I purchased like this and I knew. This boat is going to be my last boat and I am willing to re do and re check everything and cruise in serenity. Yes before selling them I wish to overhaul them... better than selling like this with some corrosion and dusty points... It is my way of doing... compression test and big check. Anybody would be interested please come back to me in private. I have no idea of the price for the 2 engines. Thank you.