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Old 08-31-2016, 10:21 AM   #161
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Originally Posted by bayview View Post
My Carver was heavily built and the AP worked well at all speeds even on one engine.

I meant to mention that "one engine" thing, too, since that's our usual trolling mode. The AP usually works fine.

There are some times when wind, and sometimes current, can overpower the AP's ability to maintain a steady course on one engine, but that goes away when we turn on the other engine and re-adjust the trolling valves... and usually in those instances, we'd also need both engines to make the right speed directly into the wind anyway.

-Chris
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Old 09-01-2016, 08:31 PM   #162
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I meant to mention that "one engine" thing, too, since that's our usual trolling mode. The AP usually works fine.

There are some times when wind, and sometimes current, can overpower the AP's ability to maintain a steady course on one engine, but that goes away when we turn on the other engine and re-adjust the trolling valves... and usually in those instances, we'd also need both engines to make the right speed directly into the wind anyway.

-Chris
There was a guy next to my slip with some kind of a two engine express cruiser. Once in a while he would return on one engine, and he could not turn into his slip without being pulled with dock lines by helpers. I don't think a boat like that will steer well in moderate sea conditions at low speed regardless who or what does the steering. For those small rudders to provide enough transverse thrust, certain speed is needed particularly in confused sea conditions. Have you ever encountered conditions when you had to slow down and have trouble maintaining the course?
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Old 09-01-2016, 08:34 PM   #163
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No, not only is it not safe to assume, that's a totally erroneous assumption. Autopilots have adjustments and can be tuned for conditions. in fact, the autopilot, properly adjusted, will maintain the course far better than one can manually.
Can you turn your boat into a slip in a marina with a narrow fairway without using differential steering or thrusters?
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Old 09-01-2016, 08:55 PM   #164
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Lost

You must be listening to some salesman.
I am a scientist, so I don't listen to salesmen at all.
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Old 09-01-2016, 11:11 PM   #165
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Can you turn your boat into a slip in a marina with a narrow fairway without using differential steering or thrusters?
What does that have to do with the section of mine that you quoted, which was discussing the use of autopilots and maintaining course using them with Sea Rays and Carvers. I don't use an autopilot to put the boat in a slip in a marina with a narrow fairway.
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Old 09-02-2016, 06:27 AM   #166
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What does that have to do with the section of mine that you quoted, which was discussing the use of autopilots and maintaining course using them with Sea Rays and Carvers. I don't use an autopilot to put the boat in a slip in a marina with a narrow fairway.
If you cannot steer the boat with the helm at certain conditions, I suppose an autopilot will be ineffective at similar conditions. With my last sailboat, I needed more than a knot or a knot and a half of boat speed to turn into a slip. Incidentally, the same minimum speed was needed for an autopilot to function properly.
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Old 09-02-2016, 07:31 AM   #167
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There was a guy next to my slip with some kind of a two engine express cruiser. Once in a while he would return on one engine, and he could not turn into his slip without being pulled with dock lines by helpers. I don't think a boat like that will steer well in moderate sea conditions at low speed regardless who or what does the steering. For those small rudders to provide enough transverse thrust, certain speed is needed particularly in confused sea conditions. Have you ever encountered conditions when you had to slow down and have trouble maintaining the course?

Yes, in many twin engine boats -- with high winds in snotty seas and running on one engine -- the AP may have some problem. So would I, if steering manually. Moderate seas, probably no problem. Windage is our more common issue.

But then running on one engine in a twin boat is what I'd consider a special case, and it comes with other issues like transmission lube, shaft lube, etc. so speed usually must be controlled to deal with that other stuff.

Anyway, I'd consider all that just a fact o' physics, not a particular criticism of one style of boat, one brand/model of AP, etc.

OTOH, with both engines running, at any speed, I've never yet encountered a situation where our AP couldn't maintain course. Our "slow" in cases where we're actually trying to go somewhere would usually be in the area of 7-8 kts. When trolling, that's closer to 2-2.5 kts.

Discussing the AP and docking in the same sentence doesn't make much sense to me.

I may or may nor be able to dock on one engine. That partly depends on which engine, and the details about the slip itself. I just had a one-engine episode, actually, but the wrong engine was running to be able to get into our own slip. Had it been our starboard engine running, I could have put the boat into our slip which is on the left side of our fairway, assuming one crew aboard to handle the spring line (which is a pretty normal docking tool for us, anyway).

Given that I was running on the port engine, and single-handing... and given there is a useful usually-empty "bail-out" slip -- straight bow-to entry -- at the end of my own dock anyway, I just put the boat in there, instead. Could have anchored to address the real (engine) problem. Could have landed at the fuel dock or somewhere else conveniently staffed. So I had options. No big deal.

And an AP wouldn't have been a useful tool for any of that docking stuff, anyway.

-Chris
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Old 09-02-2016, 08:46 AM   #168
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Regarding slow speed; I guess it's all relative. My prairie does around 8 max. Running 6.3 is my usual. When out in above 3' following seas the autopilot can't keep the course. It takes too much time to correct. And when it does it applies counter rudder too much, too late.

All the yawing and slewing around tends to make guests queezy.

I do a better job by hand in heavy following seas. (Thanks for the suicide knob).
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Old 09-02-2016, 09:39 AM   #169
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I am a bit confused as to the real question. In my limited experience, APs do a fine job at low speed, better ay course keeping than I do myself. Low speed is relative however. In my sailboats, the AP had no problem holding a course with a boat speed of 1 kt or better. Those sailboats had a real rudder and and fin keel however. My AP on my NP43 has no problem holding a course at a boat speed of 4 knots, but we usually cruise at 6.5 to 7 knots.

As BandB mentioned earlier, if your AP is setup properly for the boat you have, it should be able to hold a course at a lower speed just fine. Keep in mind I have no experience with trolling speeds in a power boat.
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Old 09-02-2016, 10:22 AM   #170
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Regarding slow speed; I guess it's all relative. My prairie does around 8 max. Running 6.3 is my usual. When out in above 3' following seas the autopilot can't keep the course. It takes too much time to correct. And when it does it applies counter rudder too much, too late.
.
I would suggest you work with the adjustments and sensitivity of your autopilot as any I've ever used could be adjusted to do just as you want in those conditions. I don't know what AP you have so can't say exactly what capabilities it has. Ultimately you should be able to mimic what you'd do by hand with the AP, just more consistently and with less work using the AP.
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Old 09-02-2016, 12:53 PM   #171
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Old 09-02-2016, 03:52 PM   #172
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Turbo Charged engines should get better fuel economy as they use exhaust energy to increase the intake pressure. Without a turbo charger the exhaust energy that the turbo extracts is just wasted. Of course you have to be running at a high enough RPM to get the turbo to "spin up". Depending on the engine you could increase your fuel economy by around 10%.
Don,

I doubt the turbo would give better economy. There's a lot to a turbo and a lot of losses. The big advantage of a turbo is that it gives more power from the same sized engine. I see only a disadvantage with boats and cars and would never have one (again). In an airplane, where you get more power at altitude they will be faster but not usually more efficient. I've had them, too.

I could argue strongly for a the largest engine you can get, normally aspirated and operate is at lower power for economy, but have the option to go fast, if money was no object.

Im not a turbo fan this week.
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Old 09-02-2016, 05:22 PM   #173
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Don,

The big advantage of a turbo is that it gives more power from the same sized engine. I see only a disadvantage with boats and cars and would never have one (again).

Im not a turbo fan this week.
Every car I've ever owned has been a turbo, I believe. Boats turbo too. Turbo was once new and unknown and problematic from lack of knowledge as well as some poorly built but now they're pretty routine.
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Old 09-02-2016, 07:36 PM   #174
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If you cannot steer the boat with the helm at certain conditions, I suppose an autopilot will be ineffective at similar conditions. With my last sailboat, I needed more than a knot or a knot and a half of boat speed to turn into a slip. Incidentally, the same minimum speed was needed for an autopilot to function properly.
Not sure what you are after.

Absolutely some twin engine boats are difficult to operate on one engine and going slow the autopilot would be ineffective ......and?

Even the worst handling boats I have driven in open water will respond on one engine and autopilot.

Coming into a marina is a different ballgame.

What REALLY are you looking for?
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Old 09-02-2016, 07:36 PM   #175
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The only turbochargers my family, in all its generations, "had" was the B-17 my father flew. (It was no match for the flak over Germany, however.) ... Since a turbocharger allows a given engine to create more power, wouldn't it wear out quicker than a naturally-aspirated one?
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Old 09-02-2016, 07:46 PM   #176
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Turbos have been around for along time. Yes, more power for smaller volume engines but also a good use of exhaust gas. Maintenance on charge coolers, etc, but overall a good thing, IMO.

BTW, My wife's Uncle flew B17s over Germany as well. On one sortie only 2 of them came back alive. The greatest generation.

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The only turbochargers my family, in all its generations, "had" was the B-17 my father flew. (It was no match for the flak over Germany, however.) ... Since a turbocharger allows a given engine to create more power, wouldn't it wear out quicker than a naturally-aspirated one?
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Old 09-03-2016, 06:43 AM   #177
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What REALLY are you looking for?
Something that I can live on full time, preferably outside of marinas for long stretches (3-6 months at a time). Seasonal migrations from Florida/Bahamas to New England with occasional trips to Puerto Rico and the islands, if possible. Most likely I will not have help operating the boat, i. e. will be singlehanding it all the time. Hence, will need to rely on an autopilot in the "thorny pass" conditions (5-6 knots of speed in 6-8 foot seas for 300 miles) including taking short naps on passages. A sailboat makes sense for this, but I don't want to live in a conch shell for a cabin, and having a draft under 4 feet would be nice.
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Old 09-03-2016, 06:53 AM   #178
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The only turbochargers my family, in all its generations, "had" was the B-17 my father flew. (It was no match for the flak over Germany, however.) ... Since a turbocharger allows a given engine to create more power, wouldn't it wear out quicker than a naturally-aspirated one?
My Dodge pickup with a Cummins 6BT 220 is turbo charged. Have 418,000 miles (approximately 8,300 hours) on the engine with original turbo (not liquid cooled). As long as you don't try to get ridiculous amounts of HP out of an engine and keep the oil clean, modern turbos don't seem to shorten engine life.

You and I have the same JD 4045 engines other than mine is turbo. Think we both burn around 2 GPH. Doubt either one of us will ever rebuild those engines.

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Old 09-03-2016, 07:38 AM   #179
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Most likely I will not have help operating the boat, i. e. will be singlehanding it all the time. Hence, will need to rely on an autopilot in the "thorny pass" conditions (5-6 knots of speed in 6-8 foot seas for 300 miles) including taking short naps on passages.

Sometimes everything bad that can happen comes together all at once... and if that happens to you, you'd just have to bite the bullet, stay awake, and steer for 300 miles.

But more often, everything that can go wrong doesn't actually do all that at the same time. Good to consider planning for it, but... If you're in a boat with working twins and 6-8' seas, AP should handle 6-8' seas. If you lose an engine, seas states might be kinder at the time, so AP should handle that anyway. And so forth.

6-8' seas in the ocean with a kindly wave period are no big deal anyway. It'd be pretty grim around here, but then I'd only have to steer for a few miles.

300 miles? Lots of short hops available throughout most of the area you describe.

Probably not too hard to find temporary crew for longer runs, if necessary.

Several ways to skin a tiger...

-Chris
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Old 09-03-2016, 08:08 AM   #180
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With the modern electronic engines, you will get a continuous read out of your fuel burn. This is data I recorded over two seasons. Our boat is a Helmsman 38. Cummins QSB 5.9 HO. We displace about 26,000 pounds depending upon fuel and water loads. We swing a 5 blade propeller, 24 x 16.75. YMMV

https://www.dropbox.com/s/mx0swc4gqj...ook1.xlsx?dl=0
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