Get Home (Maneuvering Only) 2nd Engine

[neworleansrich]

Maybe this title is misleading, but I’m not sure what else to call this idea.

First some background: A friend has a 1989 61ft Hatteras (nice roomy, well built boat, great Bahama cruiser). Back in the day it was built to plane with twin 12v71’s. Repowering to make it a real LRC or trawler speed boat would be very expensive. Lately, he has been running it around at trawler speed. He can either run both engines just above idle, or run one engine at a time (the preferable option). Running on one engine he can get about one gallon per mile at 8kts. The boat has a modern autopilot which tracks ok under one engine.

We recently brought the boat back up from the Bahamas to New Orleans and while sitting around the pilothouse during the trip we debated the pros and cons of repowering along with other ideas to help run the boat more efficiently. We started thinking about removing one prop for the bulk of the Gulf crossing. We could pull one prop in the shallows on the Gulf side of the Keys and reinstall it in the Mississippi Sound or vice versa. Obviously, pulling a prop for the crossing would eliminate the redundancy of the main engines and reduce maneuverability (though the thruster helps in that regard). Without the deadhead prop, the boat would track better with less drag and eliminate the shaft and gear rotation (the Twin Disc people say the gear can take the free rotation as long as the engine is started and run every 8 hours).

Anyway, the idea we are now discussing is replacing one prop with a folding or feathering prop. Maxprops and other brands are available for the 2.5 inch shafts, though they are not cheap. The idea is not necessarily to power the boat with this; rather the folding prop engine would be used only as a maneuvering engine or as a get home engine. The other engine would be used as the primary propulsion engine.

So what do you think guys? Repowering would mean cutting a hole in the side of the hull to get the 12v71’s out. One boatyard thought they could do it for around $200k. The boat is probably worth $325k and may be worth no more even if it was repowered. The 12v71’s are in ok shape, but running them slow is not helping their lives. Any downsides? alternatives?

 

[magicbus]

As I started to read this post my first thought was "I'd see if I could find a folding prop like I have on my wing engine". Seems you are ahead of me. Now to find one that matches the non-folding one to match when using both.

Dave

 

[neworleansrich]

Why match it? The pitch can be set on some versions like the Maxprop, but if you are using it only as a get-home or maybe just to twist the boat around while docking, who cares if they match.

On the 61ft Hatteras, I think the props are 29x29 on a 2.5inch shaft. Big bucks for a new Maxprop but seriously less than repowering.

 

[hollywood8118]

better yet do both and alternate.
But know that you are doing nothing for the value of the boat.
The cost of the props will go a long way to the fuel you will use both engines under a moderate load


HOLLYWOOD

 

[neworleansrich]

Doing both and alternate would be great but I'm not sure we can get a max prop that can drive a 61ft Hat. Maneuver at low speed maybe.

 

[FF]

Sell the boat , purchase a more suitable boat to snail cruse .

 

[ranger58sb]

Running on one engine he can get about one gallon per mile at 8kts. The boat has a modern autopilot which tracks ok under one engine.

Just confirming: you're saying the engine burns 8 GPH at 8 knots? What RPMs is that?

What's the burn rate at 200 RPMs above idle (if that's lower than above)? What speed over ground does that render? What's the burn rate at 6 knots?

I'm wondering if slights mods to speed might make it more clear whether repowering or re-propping is worth the time and cost...

And of course my guess is that repowering a $325K boat would result in a $326K boat with new engines...

-Chris

 

[Captain K]

Ditto FF.

 

[Xsbank]

Idling along will kill those engines anyway so you will get to spend the money on them in any event.

How does fuel cost compare with the rest of the ownership costs? I know the variable costs, cash flow stuff is the worst as interest rates are so low right now that capital costs are almost immaterial (did I say that out loud?), but it seems he has the wrong boat. I think he should sell up, realize as much as he can from this boat and buy a nice single with a bow thruster. A 45-50 footer will give you plenty of space, lower haul costs, lower moorage and surprise(!) lower fuel costs.

Or charter or get a partner.

 

[123]

Idling along will kill those engines anyway so you will get to spend the money on them in any event.

How does fuel cost compare with the rest of the ownership costs? I know the variable costs, cash flow stuff is the worst as interest rates are so low right now that capital costs are almost immaterial (did I say that out loud?), but it seems he has the wrong boat. I think he should sell up, realize as much as he can from this boat and buy a nice single with a bow thruster. A 45-50 footer will give you plenty of space, lower haul costs, lower moorage and surprise(!) lower fuel costs.

Or charter or get a partner.

Maybe I miss something but he owns a "Defever 48"

Removing a prop is a good idea when planning a long voyage with boats designed in an era that the price of fuel was not an issue.

 

[Bay Pelican]

Friends had similar boat repowered in the Turks and Cacios for $60,000 (US) in 2009.

If this is the Hatteras model with the main stateroom aft of the engines on the lower level I think you should consider whether it is in fact a good cruising boat, particularly for southern waters. My friends ran the generator and the AC each night to be able to sleep because the stateroom did not receive a breeze.

They may be the only trawler I have run across to regularly run the AC at anchor in the Eastern Caribbean.

For $325,000 you can find many excellent long distance cruising boats, and many many wonderful dock queens if that is your choice.

Marty

 

[BruceK]

Removing a prop is a good idea when planning a long voyage with boats designed in an era that the price of fuel was not an issue.

That might be reconsidered when, at sea in poor conditions, the engine with the prop has to be shut down. The other engine, the one with the prop removed, could be put into service, except....

 

[Xsbank]

Reiziger, he is talking about a friend's boat, a 61' Hatteras with 2 - 12v71s.

 

[Peter B]

Reiziger, he is talking about a friend's boat, a 61' Hatteras with 2 - 12v71s.

Precisely, so why would you stuff around doing anything other than use the boat as it was meant to be used. The cost of running it at a good hull speed (approx 10kn in a boat that size/length) in increased fuel would not come close to the cost of re-powering - or mucking about with the props only to find oneself in a sticky situation, as Bruce raised, with inadequate manoeuvring power, and yet the fuel burn wouldn't be much more than powering along on one engine, dragging the other, and would not be significantly under-loading the engines, surely. (Ducks for cover)
But really, what a way to treat a boat like that. The only analogy I can think of at short notice, is me trying to save wear on all 4 new tyres on my car, by using the space-saver tyre in place of one of them, and just going slower...

 

[Bay Pelican]

There was a suggestion to replace one prop with a self feathering Max prop to reduce drag when the other engine is used raised a question in my mind of what would it be like if both props were replaced with self feathering props so that either engine could be used alone.

The arrangement on Bay Pelican is the main engine 28" fixed prop and the offset wing engine has a large Max prop. The two are never run together except when docking. I am sure however when using the wing engine alone that the big prop, in a fixed position, is a major drag.

Marty

 

[rjtrane]

IMO don't do anything. Alternate motors when running on single. Keep them maintained. Find best RPM for fuel efficiency.

My guess is these motors will out live your friend - only used once a week to church and back.

 

[neworleansrich]

Selling the Hatteras and buying a real trawler (or cat) is the obvious option for him, but he would probably need to go down in size. The big engines are his only real negative. This Hatteras would not have been my choice, but it's a comfortable boat that handles sloppy seas better than my Defever 48. For my friend, the Hatteras' size makes more sense. For me, it's too big. No boat is perfect, but we are just trying to make what he has work.

The most probable option is to do what he has been doing: running around on one engine, alternating the hours on each one. Rough on the engines, but no one is going to plane this boat at $4 plus per gallon.

I originally posted this since there are some number of older boats with the same issue and while the folding prop on one side may seem crazy, it may help him keep what he has.

 

[rjtrane]

What's the possibility of using only 6 cylinders? Remove injectors and maybe valves 6for cylinders - I recall some current v8 motors that cut back to 4 for fuel economy. Would be a mechanical challenge. But would it work?

 

[neworleansrich]

What's the possibility of using only 6 cylinders? Remove injectors and maybe valves 6for cylinders - I recall some current v8 motors that cut back to 4 for fuel economy. Would be a mechanical challenge. But would it work?

We actually discussed this but neither of us know the real mechanical ramifications (eg. Oil distribution, firing order and the gaps created, and who knows).

It's just too bad it would be so expensive to remove the 12v71s. If it was a sport fish it would be a breeze.

 

[BruceK]

We can buy a Honda/Acura with a 6cyl which on light load operates as a 4, and a GM V8 which can run on 4cyl. No idea how it`s done, it can`t be rocket science, but I doubt you`d easily convert an existing engine.
Now I wait for someone to post that they already have.

 

[FF]

All 2 stroke Detroits have similar operating limits.

The DD get very poor when the power is below about 60%.

Thats why there are 1,2.3,6,8,12,&16 cylinder versions of many of the offerings.

Between 20 and 30 HP per cylinder they work great , have long service lives and are not bad fuel wise. 16Hp / gal

The Air Police doesnt love them tho.

Even at a slow idle the 12V71 will be thirsty , but at 240-360 HP its just fine.

The chined hull does not do well at the 8K trawler crawl , so engine replacement would hardly be worthwhile.

Sell and get a better slow speed boat.

 

[C lectric]

In Passagemaker, if memory serves correctly, somewhere in the last 5 yrs or so, was an article about a 53 MY Hat that the owners repowered from tired DD to JD.
They decided they didn't care if the boat planed so replaced the DD with JD 4 cylinders. New iron, economy, reliability and the boat had the living space which they valued.

Looking thgough archives may find the article. Cost, I have no idea.

In the Hatteras Forum around the same time there was a long running thread where another Hat owner kept his DD's but reworked things, depowered, but he did understand what he was doing.
Smaller injectors, smaller props so the engines would run at good revs making less hp and yet still run decently. Of course he knew that he could not run the boat at the old speeds ever untill all was put back the way it was. It was apparently successfull. But I emphasize he knew what he was doing, or at least had a heck of a good idea.

Applicable or not I won't say but it may be worthwhile trying to find these threads and articles.

 

[N4712]

Here's a nice video of an 53 Repower.
http://youtu.be/EqQPlavvD5I

 

[ranger58sb]

I suspect doing nothing (other than enjoying the boat, running as economically as possible) may be the most inexpensive option.

-Chris

 

[mahal]

Thanks for that great Video N4712.

 

[harbor950]

Here's a nice video of an 53 Repower.
Big Yacht RePower - Full Length - YouTube

that is a great video.

 

[Alex F]

Maybe this title is misleading, but I’m not sure what else to call this idea.

First some background: A friend has a 1989 61ft Hatteras (nice roomy, well built boat, great Bahama cruiser). Back in the day it was built to plane with twin 12v71’s. Repowering to make it a real LRC or trawler speed boat would be very expensive. Lately, he has been running it around at trawler speed. He can either run both engines just above idle, or run one engine at a time (the preferable option). Running on one engine he can get about one gallon per mile at 8kts. The boat has a modern autopilot which tracks ok under one engine.

We recently brought the boat back up from the Bahamas to New Orleans and while sitting around the pilothouse during the trip we debated the pros and cons of repowering along with other ideas to help run the boat more efficiently. We started thinking about removing one prop for the bulk of the Gulf crossing. We could pull one prop in the shallows on the Gulf side of the Keys and reinstall it in the Mississippi Sound or vice versa. Obviously, pulling a prop for the crossing would eliminate the redundancy of the main engines and reduce maneuverability (though the thruster helps in that regard). Without the deadhead prop, the boat would track better with less drag and eliminate the shaft and gear rotation (the Twin Disc people say the gear can take the free rotation as long as the engine is started and run every 8 hours).

Anyway, the idea we are now discussing is replacing one prop with a folding or feathering prop. Maxprops and other brands are available for the 2.5 inch shafts, though they are not cheap. The idea is not necessarily to power the boat with this; rather the folding prop engine would be used only as a maneuvering engine or as a get home engine. The other engine would be used as the primary propulsion engine.

So what do you think guys? Repowering would mean cutting a hole in the side of the hull to get the 12v71’s out. One boatyard thought they could do it for around $200k. The boat is probably worth $325k and may be worth no more even if it was repowered. The 12v71’s are in ok shape, but running them slow is not helping their lives. Any downsides? alternatives?

I know exactly what you're describing as I was experimenting cruising on one engine past season. My approach was slightly different. I have planing hull and great engines. My goal was simple, cut down fuel burn and the engine hours (obviously, if I'm going slow I'm adding hours). So, my idea was if I use one engine at a time I'll be cutting the hours in half.

From technical standpoint there are two primary items I was looking at:

1. Shaft cooling and lubrication. This is not an issue with my boat since I have crossover cooling.

2. Transmission freewheeling. This was my biggest concern. I couldn't get an official word from ZF whether my trainy can freewheel, but after consulting with few very experienced folks/mechanics I concluded that it's not "healthy" for the trainy to freewheel. So, my solution was to lock the shaft when the engine is off.

Cruising Observations:

My hull speed is 7.4kts, which I achieve at 1000rpms with both sides running. This gives me 2gph on each side (4gph total). When I shut one side down I need to bump the working side to 1200rpms and in exact the same conditions I'll make 6.5-6.9kts burning 3gph. After my initial test my conclusion was obvious. I'm saving 1/2 the hours and experiencing only minor speed loss. BTW, during my test I didn't find a difference in speed with shaft locked vs. freewheeling.

I came up with the simplest way to lock a shaft (using a line) and when I was cruising long distance it was very simple process to lock/unlock a shaft. It takes me under 30 seconds to lock/unlock it.

While cruising I'm always using AP. It has no problems staying on track with about 10-12 degree angle when running on one engine with the other side locked. The only time I see that AP is working hard is when the seas are rough. My RPMs always stay the same, 1200rpms and my speed varies depending on tides, wind and seas. In normal conditions I usually see around 7kts. But, I've cruised between 4.5 (against the tide) and as fast as 10+kts (with the tides) on one engine.

My approach is simple, I fire up both sides when I'm departing. This gives me maximum control in closed quarters. Then, when I'm out in open area I slow down and lock one side and shut the engine. After cruising as long as I need and getting within few miles from my destination, I fire up the locked side, warm up the engine, slow down to unlock the shaft, cruise for few minutes slow with both sides engaged and then jump on plane for few minutes to "clean" anything like unburned fuel and other stuff in the block and turbos on the engine that worked the most on that leg. When I approach a harbor, dock, moor or anchor both engines are engaged to give me full control. When I'm cruising the next time I just use the other engine to "catch up" on the same hours with the other side.

In my experience of running hundreds and hundreds of miles this approach works very well. I have the flexibility to have maximum control in close quarters, jump on plane when I need to (usually this happens in rough beam seas and when approaching the inlets) and save tons of fuel when using only one side.

My advice is to try experimenting as I did and I think you'll find that it's the best approach as it requires no modifications to anything, no extra expenses and having both engines available anytime gives you piece of mind and control.

Good luck,
Alex.

 

[Bay Pelican]

Alex

Excellent post, thanks

Marty

 

[neworleansrich]

Nice video. It is nice when someone takes the time to make a useful video and post it. Unfortunately, the 12v71s in this 61ft Hat are a different animal. There are 3 options for getting them out 1) Cut a hole in the side of the hull, take them out sideways, rebuild the hull and repaint the boat 2) Take them out through the salon floor, cut a hole in the cabin wall, take them out, then rebuild the wall of the salon and repaint 3) Take them out through the salon floor and cut a hole in the roof through the upper deck, rebuild etc. There are no doors or windows that will accommodate the engine blocks. Every time the owner has talked to a yard, they have said cut a hole in the hull. Ultimately, that is what might be done.

Also, he has Floscans and has many hours of trying different speeds and combinations. We have locked the prop with a LARGE pipe wrench and have considered installing a real shaft lock. The point of the original post was to discuss the possibility of using a folding or feathering prop on one side, thus making that engine a get-home and maneuvering engine only.

The problem with all these forums are all the useless and inane comments unrelated to the original issue. I know it's hard to believe, but he has considered selling it and buying something else.

 

[Steve]

I have sent a private message, on another subject, to your profile page.