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Old 05-09-2013, 02:37 PM   #21
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I have lost engines on twin engine boats, and always gotten in. In fact, backed into the slip. I lost steering on my single engine Blackfin. It was 12 miles out. Rigged an oar up to the swim platform made it in 6 miles before breaking the oar. Then it would just go in circles from the torque steer of the big Cat diesel. Had to be towed in. It was a bad day.

Aground in the Bahamas, but definitely not a bad day.

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Old 05-09-2013, 02:53 PM   #22
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I have lost engines on twin engine boats, and always gotten in. In fact, backed into the slip. I lost steering on my single engine Blackfin. It was 12 miles out. Rigged an oar up to the swim platform made it in 6 miles before breaking the oar. Then it would just go in circles from the torque steer of the big Cat diesel. Had to be towed in. It was a bad day.

Aground in the Bahamas, but definitely not a bad day.
Did you make the crossing in the inflatable??

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Old 05-09-2013, 02:59 PM   #23
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Did you make the crossing in the inflatable??

Good shot. No. Moonstruck was anchored around the corner. It was a soft grounding on the beach. After we get there, I put more miles on the inflatable that Moonstruck. It's our "car".
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Old 05-09-2013, 03:08 PM   #24
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One engine breakdown, he could only go in circles on the other engine, towed him in.

Interesting. All the twin engine boats I've ever seen in the big Seaview yard in our marina, including ours, have rudders. But I suppose if your dad's boat didn't have rudders losing an engine could be a problem.

We've brought our boat back on one a few times, all due to raw water cooling problems, not engine problems, except the one time I let an engine get a slug of air during a fuel transfer-- my fault, not the system's fault. One of the runs was six hours on one engine. I do not recall going in circles during that run but it was a number of years ago so I may have forgotten that we did.

And having twins does not automatically mean running gear damage in a grounding. As I mentioned earlier, a Grand Banks with its keel that extends considerably below the props and rudder, will lie over on its side with the downside running gear totally protected in the open space between the chine and the bottom of the keel, which is what the boat sits on when the tide goes out.
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Old 05-09-2013, 03:21 PM   #25
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Good shot. No. Moonstruck was anchored around the corner. It was a soft grounding on the beach. After we get there, I put more miles on the inflatable that Moonstruck. It's our "car".
I'm just jealous. We've never been. Hopefully this fall, after we get the new boat sorted out, then we will go over.
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Old 05-09-2013, 03:27 PM   #26
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Jim, it was immediately west of the Antioch Bridge, in the main channel on April 25. It wasn't there/visible when we returned several days later. Presumably, it's slowly working its way westward.
Hopefully it worked it's way into the junkpile in Mayberry Slough. It still amazes me that Sac County has never done anything about that eyesore.
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Old 05-10-2013, 08:46 AM   #27
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We have lots of debris in the river after really high tides and/or heavy rain. Several of our friends with Searay's have had to replace props, rudders and shafts after hitting partially submerged logs. The boats that really scare me are the ones with the pod drives. There is one Tiara in our marina with them and I'd hate to think of the damage if he were to hit something big at speed.
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Old 05-10-2013, 09:22 AM   #28
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I'm just jealous. We've never been. Hopefully this fall, after we get the new boat sorted out, then we will go over.
Great! Hope you first trip is a good one. I recommend the Abaco area for a first trip or any other trip for that matter to the Bahamas. Depending on speed you will have one or two days to Ft. Pierce. When the weather is right, hang a left and head over to the Little Bahama Bank. Enjoy.
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Old 05-10-2013, 09:42 AM   #29
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compromise

Here is a different look at recessed props from my 38 semi displacement hull. Note that the keel is safely quite a bit below the twin props. Considering that everything in boat design involves compromise, I do think, because I regularly run in low water and regularly scrape bottom, this particular design has been good for me. Knock on wood but no prop or strut or shaft damage in two years. A little glass thickening on the keel is about it. The compromise I face with this configuration is poorer steering in following seas and a bit more roll than I would like in rough water. As well my max WOT is about 21 mph.
Being able to operate like an economical diesel trawler is nice most of the time but burning money once in a while to make waves is nice too. In western Lake Erie a full trawler (or a proper one as some might suggest) with a deeper keel would really restrict my travel.
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Old 05-10-2013, 09:47 AM   #30
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The common denonator here from reading the posts and from my own experience is not prop protection, its boat speed.

Take my boat for example. It has twins and a full keel.

At a 15 knot fast cruise things happen quickly. Logs are much harder to avoid. The bow is higher which means if we do hit a log it has a tendancy to be pushed under the boat, into the running gear. The higher bow also reduces visibility

Now take the same boat at 8 knots. Going slower provides manuvering time. The bow is flat in the water which helps push logs out of the way if you do hit one. Visibility is at its maximum which provides for increased hazard recognition.

Now take my old boat, and what actually happened to me.

We had a 34' Bayliner 3488 Avanti. This was a full planing hull boat, with a flying bridge, a lower helm and with 630 horsepower a 26 knot cruise speed.

I was offshore in Alaska and hit a log going full speed. Both rudders bent back, and the rudder shafts started some serious flooding of the engine compartment. With our owner installed oversized bilge pumps we were able to make it back to port where we had called ahead and had the travellift standing by.

The boat sustained over $40K in damage including one of the cummins diesel engines which had ingested seawater into the air intake system because of the seawater being sprayed onto the air cleaner for several hours. Both rudder assemblies, both props, struts, damage to the hull. It was an extensive list.

We impacted at 26 knots. If we had been running at 8 knots, same boat I'd dare say the damage would have been much less, and possibly eliminated.
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Old 05-10-2013, 10:21 AM   #31
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I have talked to some Sea Ray and Carver owners that love their boats because they can go slow for economy, but have the option of going fast if needed. Its an appealing argument.

I've got a buddy with a 29' Sundancer (SeaRay), single 7.4 carb, Bravo3 I/O. I put a FloScan on for him. He gets about 1.5mpg at displacement speed and about the same just up on step (~28mph) - he can go 40mph but no data at that speed except the mpg is well into fractions.



Big Duck is 28' w/ Chevy 350 carb, single prop I/O and I often see better than 3mpg at 6 - 8 mph. We're supposed to be able to go 30, but never had the urge to go that fast.



Bigger boats, MPI's, twins and diesels may be different?

BTW - You see each of the boats in it's natural habitat - the 'bubble boat' likes marina cleats, Big Duck likes anchors/beaches.
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Old 05-10-2013, 10:33 AM   #32
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Pluto,
Back to the original question and notwithstanding the jokes about my father-in-law's old boat having no rudders. Rudders come in different sizes and effectivenesses. I was only suggesting that running on one engine should be part of a seatrial for your prospective boat b/4 you count on it as a get home device.
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Old 05-10-2013, 11:07 AM   #33
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Since the propwash is going backwards at high speed and blasting over the rudder trying to push it backwards and the rudder is attached to the boat the propwash is pushing the boat backwards. But of course the prop is pushing the boat forward more so the boat goes fwd but I wonder how much better the boat would go forward w/o the rudders pulling the boat backwards.
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Old 05-10-2013, 11:29 AM   #34
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Great! Hope you first trip is a good one. I recommend the Abaco area for a first trip or any other trip for that matter to the Bahamas. Depending on speed you will have one or two days to Ft. Pierce. When the weather is right, hang a left and head over to the Little Bahama Bank. Enjoy.
We're thinking about keeping it south during the winter so we can do a few trips to some different places each year.
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Old 05-10-2013, 12:20 PM   #35
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Since the propwash is going backwards at high speed and blasting over the rudder trying to push it backwards and the rudder is attached to the boat the propwash is pushing the boat backwards. But of course the prop is pushing the boat forward more so the boat goes fwd but I wonder how much better the boat would go forward w/o the rudders pulling the boat backwards.
In an earlier discussion we had about rudders, we discussed a plate type rudder split along the propeller shaftline with each section aligned with the spiral propeller race for minimum resistance. Unfortunately, when I tried this on my boat I did not have the instrumentation to measure any small gains I may have acheived.
But my feeling, after trying both the above configuration and the opposite(called a contra-rudder) as used on the Liberty Ships, was that very little gain was to be had either way for vessels our size. One type lessens drag by aligning better with propeller race, the other attempts to straighten the race spiral giving more thrust.
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Old 05-10-2013, 12:30 PM   #36
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Pluto,
Back to the original question and notwithstanding the jokes about my father-in-law's old boat having no rudders. Rudders come in different sizes and effectivenesses. I was only suggesting that running on one engine should be part of a seatrial for your prospective boat b/4 you count on it as a get home device.
I have never heard anyone with a twin regardless of make say there was insufficient rudder authority when running on one engine. On our own boat the wheel needs to be held perhaps five degrees off centered--if that-- to maintain a straight course on one engine. Our wheel is three turns lock to lock so the effect on steering by running on one is negligable.

I would say that a twin engine boat that goes in circles on one engine despite the best efforts with the rudders is a horribly designed boat, to the point I can't imagine a company even making one let alone anyone buying one.
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Old 05-10-2013, 01:03 PM   #37
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Most of the pleasure, trawler and motor yachts, twin screw are exposed. Please understand the word trawler has become another term for a displacement and/or semi displacement motor yacht. The word trawler today is more about the look of the super structure above the water line, not below the water line. Many brands use the same hull and running gear on both their trawler and motor yacht models. So to me most of this discussion is not very informative as most are pleasure. If you really want to see the difference take a walk though a marine yard that has commercial trawler, pleasure trawler, pleasure motor yachts, and you will see a the difference.


I tend to follow what the commercial do, while keeping in mind the Eagle is a pleasure wantabe commercial. I know of several larger twin screws pleasure on one engine will not steer worth a darn, and most do not have a deep draft or a keel.
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Old 05-10-2013, 01:24 PM   #38
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The term/expression "exposed" re the propellers (mostly) on trawlers is fine or safe if you kiss the bottom but the real issue is when you are "hard" on the bottom and can't move or even more typically you anchor and find the water far from your boat at low tide.

At any event when your boat is laying on the bottom most all trawlers here will heel considerably pushing their props into the sand, rocks or mud if it's a twin engined boat.

If you're on a really flat bottom and in a lake your'e in luck.

The only time I accidentally struck bottom w Willy it was a very big rock or extension of bedrock. We hit w a loud bang. I was out on the bow in my shorts in less than a minute. The boat including her prop was not damaged.
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Old 05-10-2013, 01:47 PM   #39
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At any event when your boat is laying on the bottom most all trawlers here will heel considerably pushing their props into the sand, rocks or mud if it's a twin engined boat.
That's the nice thing about the GB hull (and maybe the IG hull, too). I know of a few twin GBs that were driven aground or ended up aground when the tide went out and in these cases there was no damage to the running gear at all when the boats went over onto their sides. The keel of a GB is quite deep and extends a fair distance below the props and rudders (compared to many other boats of this type) and the wide, afterbody and hard chine keeps the boat from going over far enough to endanger the running gear.

Not that we anticipate ever going aground, but it's nice to know that if we did and the tide went out and the boat leaned over the expensive-to-repair running gear would be protected.

The much greater worry would be what would happen when the tide came back in. Would the boat start to float and right itself before the water got high enough on the downside of the boat to flood it. In one case I know of-- a GB42 woody (single) that went aground at high tide at the north end of the Swinomish Channel and was left high and dry when the tide went out-- the boat did not begin to right itself soon enough and the rising water flooded the boat and it was declared a total loss. The Vessel Assist operator in the marina at Cornet Bay on Whidbey salvaged and rebuilt it.
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Old 05-10-2013, 03:33 PM   #40
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Trawler vs. Motor Yacht

I can't speak for most MY's because I am not familiar with them.
I can speak about the 36 Mainship MY because that is what I have.

So to answer your question "Can you run one at 8 kts and hold a heading?" Yes.
Can you make tight turns or quick turns at 8 Kts? No.
At about 4-6 kts coming out from my slip, down the fairway and into the channel requires using the two engines for steering. At this speed, the rudders are useless and I rarely even use the wheel for this maneuvering. Trust me, I know the difference. I'm used to a single engine sailboat drifting into my slip and being able to make a turn with almost no forward speed.

Keep in mind that to me personally, there is a big difference between a MotorYacht Hull and a Trawler Hull. A true displacement hull almost like a sailboat hull from the waterline down. My MY is considered a semi-displacement hull - to me, it is a planning hull. It is designed to go fast and the rudders are downsized accordingly. MY steering wheel has 5 full turns from stop to stop. Most displacement hulls I am used to only have around two full turn from stop to stop.

You generally cant have high speed and economy/efficiency at the same time.
The idea that you can go faster to get out of trouble sounds good in theory. In practice, with a slow going full displacement, the owners usually keep weather in mind all of the time. While the go fast guys are speeding back to the dock, the go slow guys are looking for an anchorage. Difference in attitude I guess. Which is safer? I dunno. Most displacement hulls are made for rough weather. Most semi-displacement hulls are not. When it comes to design, you generally want light weight for speed and heavy weight for comfort.
Which design is better? That depends on how you want to travel and play.
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