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Old 20 June 2006, 18:38   #1
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What happens if.....

....you biff an outboard on something solid?

My Johnson manual has a reference to some means by which if you smack the engine on something it will tilt back up and the tilt ram will act as a shock absorber, but does this work/what happens in practice?

In other words what can you get away with - an impact at 5kt? 10kt? I presume any high speed impact is going to be terminal because of the inertia of the thing, so if you go over a partially submerged log at 30 kt you will be definitely looking for a new engine and transom....?

really just wondering at what point you do terminal damage and pull the engine up out of the water to find the bottom half has disappeared?

Glad to say I have not smacked it on anything yet (though there was a bit of a clang from the prop one day when I was trying to get it off the trailer in not quite enough water, which I think may have been a stray rock!)

Just really wondering what people's accident experiences have been so I know when to be careful and when to be really really careful

Thanks

Stephen
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Old 20 June 2006, 18:45   #2
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hit a submerged tree on the thames crossing a wier around 10 years ago in our first boat. a big bang, we stopped, all flustered i tilted up the engine and it was all fine. so at around 5-6 mph you should be fine in a light ish boat, ours at the time was a shetland saker with a suz dt85

however if you are on the plane doing some speed i would hate to think what would happen....maybe some others will share their experiences

also would far rather hit wood than a rock any day
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Old 20 June 2006, 20:41   #3
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thanks - I'd be interested in hearing any more real world experiences of what actually happened in other situations.

I guess I am worried about two things, firstly hitting a submerged rock in unknown shallow water, which is likely to be fairly low speed as I have an echo sounder and charts so will be cautious in shallow water. Second thing is hitting a bit of semi submerged waterlogged timber at high speed in open water, there are many old wrecks in the harbour and bits of timber periodically fall off them and float away. The local harbour launches quite often recover biggish bits, I have already fished one out of the water since I have had my boat, it was only about 3 foot square by an inch thick but would have hurt at 30kt I am sure.... some of the biggest timbers are 12 x 12 inches by however many feet long and waterlogged prob weigh a ton though they are thankfully rare .... just wonder what would happen if I hit one on the plane, if it was submerged the hull might just ride up over it but I hate to think what would happen to the engine
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Old 21 June 2006, 07:14   #4
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Got to admit workin in shallow water most of the time i've clipped the odd rock and submerged tree with no real problems. the main concern with these contacts for me is the damage to the prop itself. If you manage to take a chunk out of the prop or turn the edges there is every possibility that without attention any resulting vibration could eventually effect the bearings. Beside when you feel or hear the knock you'll probably knock her out of gear pretty quick before the engine gives up of it's own accord.

As for high speed impacts obviously they are more serious. most of the time the smaller branch type bits (few feet long inch or so diameterr) you find probably won't do any real damage as in most cases (from my experience anyway not that i'm suggesting you drive over them when you see them) the hull pushes them away from the leg. the larger peice ar ethe ones which will cause trouble but it also depend on the type of material you hit. Personnally I've hit a pallet at about 30knts which resulted in one hell of a bang, and the engine jumping out of the water but now real damage apart from a bit of paintwork. Admitadely it was a cheap pine on e not one of the heavy duty jobs.

Over the past 5 years i've also see atleast 3 RIBS that have had the misfortune of meeting submerged objects at high speed, from 8in x 4ft logs to entire trees. the results range from a cracked leg to the removal of the entire transom and leg withobviously terminal outcomes for the engine.

If you do have the misfortune of hitting anything solid at speed that isof any real size it's worth checking the engine, transom and hull full for damage before you go out again. Might be worth getting it check professionall if it's a good clout.
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Old 21 June 2006, 07:41   #5
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probably worth having a spare prop on board with tools etc incase you clout something
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Old 21 June 2006, 08:37   #6
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what if,!!

a few years ago i had just a speedboat (not rib) with a suzuki 40 on it, and i hit a submerged wall at high speed, the egine completely detached for the transon at the bracket part, the only thing holding the engine from going swimming was me and the gear linkage rod and the fuel pipe!! cost me about 500 (back in 1989) to put right!!
thanks to SARA LIFEBOAT,all was ok!!
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Old 21 June 2006, 09:14   #7
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Hit massive rope at 45kts, tore off entire blade of stainless steel prop...no other damage
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Old 21 June 2006, 09:43   #8
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Quote:
Originally Posted by Hugh Jardon
probably worth having a spare prop on board with tools etc incase you clout something
Don't forget your spare battery, spare engine, spare fuel tank, spare steering wheel, spare hull, spare crew, spare helmsman and spare ... ... ... ... ...

Hugh your paranoia about failure at sea is always good for a chuckle - but then I guess I would probably be the same if I had to cruise around in the wild and savage solent where you can go months without sight of land or another boat.

In all seriousness - a spare prop is not a bad idea - but changing one at sea is nigh on impossible.

I tried changing the prop from within the boat in the comfort of my own driveway and decided it was a fruitless exercise - I imediately removed my prop spanner and spare prop from the boat and made room for extra beer
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Old 21 June 2006, 10:07   #9
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roy me old mate, i have brads garmin chart he gave me to give you here so will post it in the next day or so. i did not want to give it to you while you were eating as you might have eat it as well!!!!!

as per our deep discussion at 2 in the morning around the pros and cons of having a twin battery set up. i honestly do not believe that there is any credible argument against a twin battery setup vs a single battery, remember you cant start your engine, use radio or gps or lights if one battery failed completely, losing enough power to start the engine but the radio and gps are still working is still not a helpful situation. paranoia nooo common sense...yes i believe so. my opti takes quite a bit to start it as they all do so having a second battery for the cost of 100 quid all in is not a bad backup in my book.

spare prop is useful to get you home....if jumping in the water to change a prop meant i got home and kept the family safe then i would do it with no hesitation.would be incredibly difficult i agree but not impossible as long as you dont drop the tools and washers etc

now young roy, lets get on to the kill cord discussion and driving without killcord etc etc.....not sure a defence on that one would stack up either, i do believe you have purchased a second so if you did get spat out the kids could drive the boat back to you. i have a spare but not needed as on mercury they use a flick up/down switch so can motor back without a killcord but a second means the best possible safety scenario.

paranoia.....hopefully not......being safety conscious and not blazzay yes, remember some of us were not born on the back of a fishing boat like you good old salty sea dogs in lovely cornwall

ps that new bruce anchor is the dogs and a very good investment so you cant take the piss there.

all i need to do now is replace my bailer twine before you say it
Quote:
Originally Posted by roycruse
Don't forget your spare battery, spare engine, spare fuel tank, spare steering wheel, spare hull, spare crew, spare helmsman and spare ... ... ... ... ...

Hugh your paranoia about failure at sea is always good for a chuckle - but then I guess I would probably be the same if I had to cruise around in the wild and savage solent where you can go months without sight of land or another boat.

In all seriousness - a spare prop is not a bad idea - but changing one at sea is nigh on impossible.

I tried changing the prop from within the boat in the comfort of my own driveway and decided it was a fruitless exercise - I imediately removed my prop spanner and spare prop from the boat and made room for extra beer
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Old 21 June 2006, 11:47   #10
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Quote:
Originally Posted by roycruse
In all seriousness - a spare prop is not a bad idea - but changing one at sea is nigh on impossible.

I tried changing the prop from within the boat in the comfort of my own driveway and decided it was a fruitless exercise - I imediately removed my prop spanner and spare prop from the boat and made room for extra beer
I would regard the advantage of having a spare prop on board being that you could toddle in to the nearest suitable beach on the aux engine, pull it up on the beach, change it and then carry on using the main engine to wherever you were going rather than chugging along at 4 knots.

I've even wondered how you would get on taking a rope off the prop if you were at sea, I think it would be very difficult, and if there was rope in the water you couldn't even use the aux....

Any more broken boat stories please?
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