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Old 11-19-2013, 07:19 PM   #1
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Get Home (Maneuvering Only) 2nd Engine

Maybe this title is misleading, but Iím 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 12v71ís. 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 12v71ís 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 12v71ís are in ok shape, but running them slow is not helping their lives. Any downsides? alternatives?
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Old 11-19-2013, 07:29 PM   #2
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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.

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Old 11-19-2013, 07:36 PM   #3
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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.
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Old 11-19-2013, 08:40 PM   #4
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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


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Old 11-19-2013, 09:23 PM   #5
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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.
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Old 11-20-2013, 05:59 AM   #6
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Sell the boat , purchase a more suitable boat to snail cruse .
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Old 11-20-2013, 08:37 AM   #7
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Quote:
Originally Posted by neworleansrich View Post

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...

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Old 11-20-2013, 09:01 AM   #8
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Ditto FF.
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Old 11-20-2013, 12:50 PM   #9
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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.
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Old 11-20-2013, 08:22 PM   #10
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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.
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Old 11-20-2013, 09:18 PM   #11
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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.

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Old 11-20-2013, 11:40 PM   #12
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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....
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Old 11-21-2013, 02:18 AM   #13
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Reiziger, he is talking about a friend's boat, a 61' Hatteras with 2 - 12v71s.
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Old 11-21-2013, 06:22 AM   #14
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Quote:
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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...
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Old 11-21-2013, 07:16 AM   #15
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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.

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Old 11-21-2013, 07:21 AM   #16
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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.
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Old 11-21-2013, 09:42 AM   #17
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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.
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Old 11-21-2013, 06:48 PM   #18
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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?
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Old 11-21-2013, 07:16 PM   #19
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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.
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Old 11-21-2013, 10:46 PM   #20
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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.
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