chuzzlewit
Well-Known Member
The boat is a Merry Fisher 805, about 27ft. I aim to fit an outboard bracket on the bathing platform before going to the Channel Islands.
What HP for an emergency get-you-home outboard?
- Thread starter chuzzlewit
- Start date
rustybarge
Well-Known Member
Iv'e got a Tohatsu 6 hp saildrive extra long shaft outboard on my 25' 1.5 ton catamaran....very pleased with it
Light enough to lift on and off the transom at 26 kg.
Great grip in the water with high trust prop.
Extra long shaft 25" stays in the water even in choppy conditions.
Cruises at about 5-6 knots even against the wind and waves.
Bad points:
Cheap low quality mouldings ( same as the competition)
Extra long shaft is really really long.....don't ask how I know
Needs lots of choke to start even in hot weather.
Hood is made from paper thin plastic, catch has fallen off already.
Overall: 9/10. Gutsy little O/B, runs well at all revs.
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Canopy Locked
Well-Known Member
I'd suggest that an 805 weighs a little more than 1.5T
From my experience, I used to have a Hardy 24 (around 4t weight - very roughly). When I bought the boat the previous owner had fitted a 15HP Yamaha long shaft to a bracket on the swim platform. I tried it out when doing the sea test (on the clyde) and it moved the boat. I tried it out in the North Sea one day, on a relatively calm day - waves and swell, but by no stretch of the imagination could it have been called rough! - The O/B could not move the boat.
I took off the outboard and sold it.
If I was you, rather than waste your money on buying an outboard engine, that will have doubtful practical use and will require you to carry a 2nd fuel supply, invest in some good primary fuel filters that can be changed at sea. Most diesel engine problems occur due to fuel problems.
MarieK
Well-Known Member
Is your main engine petrol or diesel? If diesel and you have to carry petrol for the outboard then you will not be able to carry enough to carry you home from mid channel!
Oscar24
Well-Known Member
Had a mate with a 21ft 3Ltr inboard petrol bayliner cuddy, conked out once off old harry rocks.
No problem he says, ive got an outboard.
Outboard was a 7 1/2 Hp mercury long shaft.
We managed to limp back into Poole, but it was painfully slow cir 2Knots max. Fortunately we had the tide with us.
If we hadn't of had the tide i think it would have been next to useless.
agree totally with robmchugh.
Spend the money on proper servicing, a working radio and maybe for peace of mind Sea Start membership (although i dont know how far of the UK they work)
No problem he says, ive got an outboard.
Outboard was a 7 1/2 Hp mercury long shaft.
We managed to limp back into Poole, but it was painfully slow cir 2Knots max. Fortunately we had the tide with us.
If we hadn't of had the tide i think it would have been next to useless.
agree totally with robmchugh.
Spend the money on proper servicing, a working radio and maybe for peace of mind Sea Start membership (although i dont know how far of the UK they work)
ontheplane
Well-Known Member
The 805 is about 3 tonne (ish) - given that the power required goes up roughly in line with weight (very approx) then for inland use I think you'd need a 5-10hp - coastal I'd want to double that at least - 30-40hp. You would also HAVE to have a sailpower / bigfoot, Hi-Thrust type - a standard outboard of less than about 70-80hp would be useless. Saying all that, I am not sure I agree that it's pointless to have one.
If you had a major failure, at least with an outboard, you could adjust your speed and course, even if you couldn't punch against wind and tide. So rather than aimless drifting, you could use the o/b to use wind and tide to help you get somewhere safer rather than deeper in the mire.
If you had a major failure, at least with an outboard, you could adjust your speed and course, even if you couldn't punch against wind and tide. So rather than aimless drifting, you could use the o/b to use wind and tide to help you get somewhere safer rather than deeper in the mire.
rustybarge
Well-Known Member
Totally agree, at least a small O/B will give you some sort of steerage, even if you do have to turn downwind to make headway.
maby
Well-Known Member
Practical experiments published in Yachting Monthly last month demonstrated that ii is possible to tow a surprisingly large boat with a 2.5hp outboard on a small inflatable dinghy if you know what you are doing.
CaptainMike1970
Well-Known Member
A little 2.5 or 3.5 outboard will probably get you around in the marina on a calm day but as a rule of thumb, I would have thought you would need 10% of the main engines power to make any sort of slow progress. As others have said anything that helps you steer out of trouble / use the tides / wind to make some sort of progress away from deeper mire is a good thing. Don't forget petrol goes "off " if not used and left in the tank.
maby
Well-Known Member
Try to find a copy of the article - it made fascinating reading!
AndieMac
Well-Known Member
Not so much if the tank is sealed and not vented, as in the 25 litre plastic outboard tanks with the vent screw closed.
You can add a stabilising product to the fuel also, but if the fuel is new at the start of the season, kept sealed, it should be fine for a few months.
Then at lay-up time just tip the remainder into the car tank, even if premixed with oil 50:1, and top up the car tank to dilute the oil further.
chuzzlewit
Well-Known Member
Thanks for your comments. I think I'll go on a Get to Know Your Diesel course.
runner911
Active Member
I run a Merry Fisher 655 out of Plymouth.
About 3 months ago I had a total and unexpected engine failure . The boat is fitted with a Volvo Penta D3110C ( not too impressed with it to be honest ). I was very lucky not to end up on rocks and had to be towed back to my berth at Yachthaven .
It transpired that the high pressure fuel pump had failed. To say the engine is pampered by me is an understatement , and I can think of no reason why the pump gave up other than sods law.
Anyway, having been scared witless by the close shave I had experienced , I decided to have an auxiliary outboard fitted. The chap who carried out the work was very honest insofar as he explained that the engine he recommended , a Mercury 6HP would not bring me home from 20-30 miles out . What it would do however is to get me away from rocks/danger etc. in the event of another engine break down.
The engine pushes the boat along at 4-5 knots in a calm sea. Any other slightly adverse conditions and it slows down to about 2 - 2.5.
I would think that with an 805 you would need at least double the power around 12-15 HP for the engine to effectively move the boat.
Hope this helps.
About 3 months ago I had a total and unexpected engine failure . The boat is fitted with a Volvo Penta D3110C ( not too impressed with it to be honest ). I was very lucky not to end up on rocks and had to be towed back to my berth at Yachthaven .
It transpired that the high pressure fuel pump had failed. To say the engine is pampered by me is an understatement , and I can think of no reason why the pump gave up other than sods law.
Anyway, having been scared witless by the close shave I had experienced , I decided to have an auxiliary outboard fitted. The chap who carried out the work was very honest insofar as he explained that the engine he recommended , a Mercury 6HP would not bring me home from 20-30 miles out . What it would do however is to get me away from rocks/danger etc. in the event of another engine break down.
The engine pushes the boat along at 4-5 knots in a calm sea. Any other slightly adverse conditions and it slows down to about 2 - 2.5.
I would think that with an 805 you would need at least double the power around 12-15 HP for the engine to effectively move the boat.
Hope this helps.
AndieMac
Well-Known Member
Think about adding a parachute sea-anchor to the kit as well, especially if planning decent off-shore cruises. Not to confused with small drogues yachties trail astern to maintain steerage in heavy following seas, a boat your size will require a parachute opening of at least seven feet.
A properly designed parachute anchor (google fisherman's para anchor or drift anchors) will hold your vessels head directly to weather, slow your (wind effected) drift rate down considerably and give you time to get yourself organised with either main engine repairs, readying the auxiliary engine or calling for help.
Don't underestimate the effect on the crew of rolling beam-on in the sea for an extended period of time, which is the normal way a boat will lay when dead in the water with a sea running, especially with your head in the bilge dealing with filter changes etc....
A properly designed parachute anchor (google fisherman's para anchor or drift anchors) will hold your vessels head directly to weather, slow your (wind effected) drift rate down considerably and give you time to get yourself organised with either main engine repairs, readying the auxiliary engine or calling for help.
Don't underestimate the effect on the crew of rolling beam-on in the sea for an extended period of time, which is the normal way a boat will lay when dead in the water with a sea running, especially with your head in the bilge dealing with filter changes etc....
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Sheppy
Well-Known Member
Hi Chuzzlewi,
An interesting thread. There are some very good points made here, and as usual, some pretty stupid ones too. It really doesn't matter how much you spend on maintenance, engine parts can fail at any time, fuel problems can start at any time, and of course no amount spent on maintenance can prevent a fouled/damaged prop etc etc.....
Having some kind of aux engine is a commendable solution and one that offers additional safety and peace of mind. That said it does have to right for the boat. A general rule of thumb is 1hp per metre but hull type and weight do have factors here too. It's also worth looking at engine types, storage, fuel etc..
I would suggest initially that you have a decent aux mount fitted, if not already done, and borrow a couple of different engines from friends, or people willing to help, and test what works best. Depending on your mount height you may need a long or extra long shaft - note that a long shaft may stay in the water in calm seas but spend half its time out of the water in larger swells. Also think about how to control from over transom - fitting, safety line, starting, steerage, etc.. It's not just a case of fitting the mount as low as possible either as the engine could just get swamped, maybe try to assess a suitable position when out in some slightly rougher seas?
You'll probably be looking for around a 10hp (9.9), being a twin will be an advantage with easier starting and less vibration stress on the mount. 4-strokes are heavy and don't offer that much torque so look for an older and lighter 2-stroke. A good 10hp 2-stroke for example will offer around the same grunt as a 13/14hp 4-stroke. I suspect that if you go much higher to about 15hp, you'll struggle to install the engine on the mount when needed, unless of course you intend to store it on the mount permanently.
A sail drive unit is also a good idea but not all come with extra long shafts. The main advantage with a sail drive is the prop, they use high thrust props that not only get heavier boats moving better but, and just as importantly, they offer significantly better thrust in reverse allowing for better stopping - easily overlooked. Many sail drives also have a charging system too which could help with a flat battery. But if the extra length and charging loom aren't important to you, just buy a long shaft and change the prop to the high thrust one.
Also note that some engines are the same whether they offer 8 or 10hp for example, so don't just assume a larger engine always weights more. IMO 2-strokes make much better aux engines, they're lighter, more reliable, store better and offer more grunt per hp.
Yes, fuel will be a problem, especially if you're planning on a CI crossing, can't really help with that one but you could just take lots of fuel on that one trip. But under normal conditions the engines you'll be looking at will have external fuel hookups so you can store say ten or fifteen litres quite easily, more if you cruise further off shore. You can test how much fuel your chosen aux will use and plan for fuel more effectively. If you go with a 2-stroke, don't mix the fuel with oil until you need it - but make a note of that on the fuel can as it might not be you hooking it all up.
And just remember to add an 'aux' plan to your normal regime - run the engine up at least every three months, two might be better, rotate the fuel every six months, carry a spare prop and pin, plugs, 2-stroke oil etc.. It's not much to add to your boating lists when you consider how much peace of mind it offers.
I do think that for the CI, it won't necessary get you there should you suffer the worst, although you never know
, but as said by others, it'll certainly allow you to keep your bow into in the waves, wind etc keeping you significantly safer than just drifting at the mercy of the waves.
Hope my rambles help in some way.
An interesting thread. There are some very good points made here, and as usual, some pretty stupid ones too. It really doesn't matter how much you spend on maintenance, engine parts can fail at any time, fuel problems can start at any time, and of course no amount spent on maintenance can prevent a fouled/damaged prop etc etc.....
Having some kind of aux engine is a commendable solution and one that offers additional safety and peace of mind. That said it does have to right for the boat. A general rule of thumb is 1hp per metre but hull type and weight do have factors here too. It's also worth looking at engine types, storage, fuel etc..
I would suggest initially that you have a decent aux mount fitted, if not already done, and borrow a couple of different engines from friends, or people willing to help, and test what works best. Depending on your mount height you may need a long or extra long shaft - note that a long shaft may stay in the water in calm seas but spend half its time out of the water in larger swells. Also think about how to control from over transom - fitting, safety line, starting, steerage, etc.. It's not just a case of fitting the mount as low as possible either as the engine could just get swamped, maybe try to assess a suitable position when out in some slightly rougher seas?
You'll probably be looking for around a 10hp (9.9), being a twin will be an advantage with easier starting and less vibration stress on the mount. 4-strokes are heavy and don't offer that much torque so look for an older and lighter 2-stroke. A good 10hp 2-stroke for example will offer around the same grunt as a 13/14hp 4-stroke. I suspect that if you go much higher to about 15hp, you'll struggle to install the engine on the mount when needed, unless of course you intend to store it on the mount permanently.
A sail drive unit is also a good idea but not all come with extra long shafts. The main advantage with a sail drive is the prop, they use high thrust props that not only get heavier boats moving better but, and just as importantly, they offer significantly better thrust in reverse allowing for better stopping - easily overlooked. Many sail drives also have a charging system too which could help with a flat battery. But if the extra length and charging loom aren't important to you, just buy a long shaft and change the prop to the high thrust one.
Also note that some engines are the same whether they offer 8 or 10hp for example, so don't just assume a larger engine always weights more. IMO 2-strokes make much better aux engines, they're lighter, more reliable, store better and offer more grunt per hp.
Yes, fuel will be a problem, especially if you're planning on a CI crossing, can't really help with that one but you could just take lots of fuel on that one trip. But under normal conditions the engines you'll be looking at will have external fuel hookups so you can store say ten or fifteen litres quite easily, more if you cruise further off shore. You can test how much fuel your chosen aux will use and plan for fuel more effectively. If you go with a 2-stroke, don't mix the fuel with oil until you need it - but make a note of that on the fuel can as it might not be you hooking it all up.
And just remember to add an 'aux' plan to your normal regime - run the engine up at least every three months, two might be better, rotate the fuel every six months, carry a spare prop and pin, plugs, 2-stroke oil etc.. It's not much to add to your boating lists when you consider how much peace of mind it offers.
I do think that for the CI, it won't necessary get you there should you suffer the worst, although you never know
, but as said by others, it'll certainly allow you to keep your bow into in the waves, wind etc keeping you significantly safer than just drifting at the mercy of the waves.Hope my rambles help in some way.
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ontheplane
Well-Known Member
Not always strictly true - many saildrive type outboards actually have a different bottom end, gearbox casing, and the higher thrust prop is often a larger diameter which won't fit on the normal model without fouling the cavitation plate. These outboards are designed to do a TOTALLY different job - a standard 8-10hp outboard is designed to drive a small, very light boat to as high a speed as possible (think dinghy, small inflatable or rib) whereas the saildrive type are geared/designed to drive a large, heavy boat at displacement speed and as such are much better for the job you want.
See if your local outboard dealer will let you try one?
Sheppy
Well-Known Member
Thanks Ontheplane, that's pretty much what I thought/assumed, but after speaking to a few dealers about sail drive units, they all pretty much said the same thing, that the gearbox's and ratios are the same and it's just a different prop. It's certainly worth more investigation as I feel these units are better suited to larger boats. Can any dealers offer some conclusive info?
longjohnsilver
Well-Known Member
That's a good move. Forget the outboard. It's just not practical.
Spi D
...
Give this some consideration:
Your main engine will, at idle, push the boat at a given speed. Driving an optimal prop etc. the hp & torque created in other words accomplish this.
Compare to an outboard. Way less prop/blade area and less usable thrust. Any small outboard will struggle under anything but ideal conditions.
Take a look at non planing boats of similar size and note their smallest recommended hp.
Agree with the maintenance & education route. Add to this a few important spare parts eg, impeller, alternator belt, filters etc. and good quality tools.
Your main engine will, at idle, push the boat at a given speed. Driving an optimal prop etc. the hp & torque created in other words accomplish this.
Compare to an outboard. Way less prop/blade area and less usable thrust. Any small outboard will struggle under anything but ideal conditions.
Take a look at non planing boats of similar size and note their smallest recommended hp.
Agree with the maintenance & education route. Add to this a few important spare parts eg, impeller, alternator belt, filters etc. and good quality tools.
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rustybarge
Well-Known Member
Taking the weights of outboards into consideration:
Up to 6hp about 25 kg
8hp- 20hp 40-50kg ( new suzuki 20hp is 44kg)
25-50hp about 75-100kg
Me, i'm weak, I can only lift on and off the 6hp......
Just out of interest the classic choices on quite big Cats up 35' are twin 10hp Yamaha's high trust.
Next available saildrive is the 40hp Yahama.
Up to 6hp about 25 kg
8hp- 20hp 40-50kg ( new suzuki 20hp is 44kg)
25-50hp about 75-100kg
Me, i'm weak, I can only lift on and off the 6hp......
Just out of interest the classic choices on quite big Cats up 35' are twin 10hp Yamaha's high trust.
Next available saildrive is the 40hp Yahama.
