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Old 02-14-2011, 12:44 PM   #21
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RE: Proper Prop

someone mention kelp can damage props, please elaborate?
we have large surface kelp areas in so callifornia, whilst we do not navigate through this habitat purposely sometimes you just find yourself in the middle of one.. i usually exit at a very low speed.
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Old 02-14-2011, 01:10 PM   #22
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RE: Proper Prop

Kelp is very tough stuff. It can get wound up on a shaft, create an out-of-balance condition, and the vibration could conceivably knock things out of alignment. I would be surprised if kelp would physically damage a prop, however. But we avoid the kelp mats because of the potential they have to foul a shaft or rudder. We've gotten a wad of kelp hung up on one of our rudders and it shakes the hell out of the rudder, rudder bars, etc. This sort of thing doesn't do the rudder bearings any good.

We also get large eel-grass mats up here. They can just about stop an outboard motor--- we've had this happen a few times--- because the long grass blades wind up tight around the prop shaft in the gap between the prop and the lower unit. The only danger it poses to boats like our GB is that the long, slender, and tough blades can thread themselves up through the holes on the external strainers over the raw water through hulls for the engines. They can then tangle up and clog the raw water intake hoses. While rare, our diesel shop tells us that the blades can even snake themselves though a sea strainer and end up in the raw water pump. So we drive around the eel-grass mats, too.
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Old 02-14-2011, 01:34 PM   #23
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RE: Proper Prop

I hit something under water once several years ago.

Going along nice an calm then, Bang.**Never knew what it was but it sure did nick up the prop.

Had to hire a diver to remove the prop and have it repaired.

*Single engine. All*I could was drive the boat home.

*Quite a vibration for 20 or so miles.

Yet when I think about it doesn't take much of a ding to cause a lot of vibration.

Because it wasn't really that bad a ding. In my opinion.

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Old 02-15-2011, 09:34 AM   #24
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RE: Proper Prop

This happened to a friend of mine (Cliff) several years ago.
He was returning to home port. Mystic, Ct from a 2 week trip to Maine in his single screw 35 Duffy.
Just off of Block I he saw nasty weather ahead and decided to pull into Block I to anchor till the tx storm passed. On his way toward the harbor he suddenly felt a bad vibration. His son dove and discovered a blade missing from his 4 blade prop.
He limped into the harbor (3 or 4 miles), found us and we (my buddy and I) rafted him. Lucky for him, my buddy had a prop that was close to his, and I had a prop puller. We both had dive gear.
His prop had simply fatigued and a blade broke off. 3 other blades had cracks near the hub.
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Old 02-15-2011, 02:25 PM   #25
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RE: Proper Prop

Bertrams used to be famous for losing propeller blades. More than one would end up sticking in the bottom of the hull.
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Old 02-15-2011, 04:47 PM   #26
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Proper Prop

Quote:
jleonard wrote:

Lucky for him, my buddy had a prop that was close to his, and I had a prop puller. We both had dive gear.
*
It sounds like (for obvious reasons) that folks with twin screws can get their boats into port with one damaged prop.*For those with single engines, do you normally carry a spare prop and gear and could you change a badly damaged prop while*underway? If you were*in a remote area or quite a distance from a tow or in danger of a lee shore and*your prop was useless, what would be your plan of action?**** KJ*

ps* this is in way meant to reignite the eternal "single vs. twins" debate.*

*


-- Edited by KJ on Tuesday 15th of February 2011 06:01:13 PM
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Old 02-15-2011, 05:35 PM   #27
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RE: Proper Prop

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KJ wrote:

what would be your plan of action?
Around here where being blown or carried ashore generally means going onto the rocks as opposed to onto a mud or sand bottom, the often-recommended practice if your boat loses power where you are in danger of being*pushed into the shoreline*is to first let your anchor all the way out to the end of its rode and secure the rode.* The water is often very deep almost up to the shoreline around here, so letting your anchor all the way out increases the chances of it catching on something and holding before you end up against the shoreline.
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Old 02-15-2011, 07:08 PM   #28
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RE: Proper Prop

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Marin wrote:


KJ wrote:

what would be your plan of action?
Around here where being blown or carried ashore generally means going onto the rocks as opposed to onto a mud or sand bottom, the often-recommended practice if your boat loses power where you are in danger of being*pushed into the shoreline*is to first let your anchor all the way out to the end of its rode and secure the rode.* The water is often very deep almost up to the shoreline around here, so letting your anchor all the way out increases the chances of it catching on something and holding before you end up against the shoreline.
Yes, I am aware of the recommendation to let the anchor out and hoping it catches before landfall.* In fact*I had to do just that*when the engine in my sailboat crapped out on the lee side of Angel Island.* No wind, late in the evening, radio not working, current setting me to shore.* Fortunately,*my anchor grabbed not too far from shore (just happened to be a designated anchorage), and*I spent*a* pleasant night on the hook.* In the morning I was able to get the engine going (replaced the stupid water impeller) and had a nice cruise back to port.
Anyway, part*of my original inquiry was kind of like if a singe engine boat suffered severe damage to the prop (and dropping anchor was not an option, say like crossing the Gulf Stream),*would*the operator (skipper)*be capable of changing the prop themselves.***KJ

*
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Old 02-15-2011, 07:17 PM   #29
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RE: Proper Prop

Quote:
KJ wrote:

if a singe engine boat suffered severe damage to the prop (and dropping anchor was not an option, say like crossing the Gulf Stream),*would*the operator (skipper)*be capable of changing the prop themselves.***KJ



If the boat was set up for it, sure, assuming someone on the boat was an experienced diver.* Famous (and true) story about a GB42 owner who wanted to move his boat from Hawaii to the mainland under its own power.* He removed the prop from one shaft and went half the distance to the mainland on the other engine and prop.* At the halfway point he dove on the boat, removed the prop he'd been running on, installed the other prop on the other shaft, and ran the second half of the trip on the other engine and prop.

I believe Carey of this forum had a prop replaced underwater by a diver in Nanaimo or some such place up north.

From what I have observed in the boatyard in our marina, the trick is going to be getting the prop off because they can jam themselves on pretty tightly.

*
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Old 02-16-2011, 12:03 AM   #30
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RE: Proper Prop

A properly designed, single-engined trawler should have a full keep to protect shaft, propeller, and rudder.* What proportion of twin-engined boats are similarly protected?
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Old 02-16-2011, 12:07 AM   #31
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RE: Proper Prop

Outside of custom installations the only twin-engine production boat I'm aware of that puts a skeg-like keel in front of each prop and rudder as protection is the Great Harbor.
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Old 02-16-2011, 10:27 AM   #32
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RE: Proper Prop

"the trick is going to be getting the prop off because they can jam themselves on pretty tightly."

Never had a problem when using*my prop puller. It works very well.
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Old 02-16-2011, 11:08 AM   #33
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RE: Proper Prop

Quote:
this gave more range? less fuel burn, enough to make a difference?






Marin wrote:
Famous (and true) story about a GB42 owner who wanted to move his boat from Hawaii to the mainland under its own power.* He removed the prop from one shaft and went half the distance to the mainland on the other engine and prop.* At the halfway point he dove on the boat, removed the prop he'd been running on, installed the other prop on the other shaft, and ran the second half of the trip on the other engine and prop.

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Old 02-16-2011, 11:26 AM   #34
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RE: Proper Prop

Per,
That's a single engine boat pack'in another engine around all the time.
Here's a better mousetrap. Notice the engines.

http://www.yachtworld.com/core/listi...g_id=1709&url=


Mark,
I think Krogen builds twins w a short but full depth keel for each propeller shaft. It really would'nt be that difficult to add keels to each shaft.
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Old 02-16-2011, 11:42 AM   #35
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RE: Proper Prop

Quote:
nomadwilly wrote:

Per,
That's a single engine boat pack'in another engine around all the time.
Here's a better mousetrap. Notice the engines.

http://www.yachtworld.com/core/listi...g_id=1709&url=

lost me on that one, looks like a regular twin GB?
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Old 02-16-2011, 12:11 PM   #36
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RE: Proper Prop

Quote:
Per wrote:

*
this gave more range? less fuel burn, enough to make a difference?


Marin wrote:
Famous (and true) story about a GB42 owner who wanted to move his boat from Hawaii to the mainland under its own power.

He ran on one engine for more range and removed the non-running prop to eliminate drag.* He switched props and engines at the halfway point so that both engines would have more or less the same amount of time on them at the end of the trip.* I have never heard if he carried additional fuel or not. I would have thought he'd have had to.* A GB42 can't come anywhere near to covering that distance on two engines and standard tankage and I would be surprised if it can do it on one engine and the standard tankage.

It was something of a stunt and nobody I've talked to on the GB forum thinks it was a smart or clever thing to do since a GB is totally unsuited for open ocean cruising.* Fortunately the weather cooperated for him.

*
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Old 02-16-2011, 01:45 PM   #37
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RE: Proper Prop

Quote:
markpierce wrote:

A properly designed, single-engined trawler should have a full keep to protect shaft, propeller, and rudder.*

So, you would*not prepare for an unforeseen event that could possibly damage your prop,*like carrying a spare and gear/tools to change it?* You would rely solely on the design of the boat to avert a potential disaster?* Is this the common*practice among single engine/prop skippers?*** ***

*
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Old 02-16-2011, 02:01 PM   #38
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RE: Proper Prop

Quote:
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You would rely solely on the design of the boat to avert a potential disaster?* Is this the common*practice among single engine/prop skippers?*** ***
We don't run a single engine boat anymore--- well we do, if you count our outboard powered Arima fishing boat that cruises at about 30 mph--- but I think relying solely on the design of the boat is a foolish practice.* You have already seen some posts by the owners of single engine boats who had their props damaged.

As important if not more important than the design of the boat is the vigilance and skill of the person on the helm.* Given the staggering number of twin engine boats that are operated in the PNW, the number of running gear strikes is, I'm willing to bet, very low.* The secret to not damaging a boat is to not run into anything with it.* That doesn't happen because of the design, it happens because the person steering doesn't let it happen.* Or perhaps better wording is does everything possible to prevent it from happening.

Carey and his wife have a single-engine lobsterboat.* They run in the same water we do, often, if we're going to the same place together, on the same basic course we're following. They put every bit as much effort into spotting and avoiding logs, branches, lumber, crab-pot floats, kelp and eelgrass mats, and all the other crap we get in the water here as we do even though his boat's prop is protected by a keel and rudder shoe.* I think Carey has a spare prop for his boat at home, but he doesn't carry it on the boat.

The boat's just a tool.* How effectively and safely that tool gets used is up to the person using it.* Yes, sh*t happens, but there's a whole lot a person can do to minimize the chances of sh*t happening * Relying on a keel and rudder shoe to keep you out of trouble is probably a pretty sure way of guaranteeing that someday, you'll get into trouble.

*
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Old 02-16-2011, 04:08 PM   #39
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RE: Proper Prop

I thought I was about as vigilant as anybody out there but running up Clarence Strait we heard a big BOOOMMM. Neutral and idle as instantly as I could. Didn't fell anything that felt like a prop strike but it must have kissed it as we did feel a new but very slight increase on vibration. We saw the log 14" X 14' about. Could have sunk us. If we had had a twin it may have been more than a kiss. When hauled we found no marks.

The 36 GB has two 4JH Yanmars* 55hp each.
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Old 02-16-2011, 10:06 PM   #40
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RE: Proper Prop

Quote:
KJ wrote:

So, you would*not prepare for an unforeseen event that could possibly damage your prop,*like carrying a spare and gear/tools to change it?* You would rely solely on the design of the boat to avert a potential disaster?* Is this the common*practice among single engine/prop skippers?*** ***


No I would not.* I've not the skills to install for example.* And if I was really worried, I wouldn't bother taking up boating.

*
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