Electric propulsion

30boat

30boat

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A friend of mine who lives aboard had the,self inflicted,misfortune of having his boat sink.The engine was completely submerged and stayed so for at least a month .Being an old BMC it's not worth rebuilding and he wouldn't be able to afford it anyway .
So we are thinking of the possibility of fitting a DC motor ,maybe from a golf buggy and connect it to the shaft with belts or chains.
He's not going anywhere far but needs to be moblle because he's lying to a swinging mooring and sometimes has to move the boat.He has solar panels already and a good portable generator.
The boat is a 33 feet 9 ton displacement motorsailor.
Any tips and suggestions will be welcome

Thanks
 
Get a secondhand BMC engine, leccy power for that size of boat in tidal waters is going to be a BIG motor and lots of batteries, solar wont do it.
I also doubt a small portable genny would do it either.
Plus its not going to be easy or cheap to fit, with thrust plates, mountings, cables, switch gear etc etc.
Electric propulsion is for small river boats, (designed to be leccy powered) or diesel-electric for big/medium ships.
Sorry, believe me, I dont want to piss on your parade, but it will be cheaper and better in the long run, to replace like with like. IMHO
 
Sad but true an electric motor from a golf buggy will not move a 9 ton boat very far .. My engine is a 15kw 21hp and it drives a 4.5 ton boat at max 6 knots .. So all your electric motor will do is act as an egg whisk .. /forums/images/graemlins/frown.gif
 
How much power does he need?

Say 20 HP? i.e. 15kW?

For how long?

Maybe an hour at a time??

So he would need about 2500 Ah of 12V battery capacity (at 50% useable). Whether he used them as a 12V bus (~1200 amps) or went for a higher voltage doesn't affect this calculation.

At about 20kg / 100 Ah this is about 1/2 tonne of batteries

Maybe £1 / Ah for deep cycle batteries is ~£2500

If he got 5 amps average charging current from his wind generator on the mooring, and the charging was 80% efficient, then he'd fully recharge in about 2 weeks, provided he didn't have any domestic use /forums/images/graemlins/smile.gif

Insert own numbers as appropriate. Not totally out of the question, but a small-ish outboard on the transom looks a better bet than a golf buggy motor if he can't sort the inboard.

Andy
 
With all due respect, your catalac, is not the same as a 33 foot, 9 ton monohull.

I would have thought a better bet was to strap a dinghy with a decent sized out board say 10hp alongside and use that.
 
By the time you'll finish fitting the electric motor and batteries it would have costed the earth. The best options are to fit an outboard motor minimum of 10hp; but by far the best way is to find another BMC engine; few second hand around. Even better, get an old Ford diesel engine from a scrap yard and do the bear minimum to marinise it.
 
can not see that being completely submerged would do much damage to the engine ?,have you tried to turn it over,if it moves change the oil,remove the injectors and crank it till all the water spray stops comeing out of the injector holes,change the oil again and start up ,run till hot ,change the oil again,if ok take of starter motor,remove backplate drain any water,flush with fresh water and place in warm oven to dry out,check the brushes have not stuck before puting back together,if it w'ont turn over, all is still not lost just a bit more to do if you need step by step help just "pm" me
 
I'd go along with Cap Fantastic/Ocean Pilgrim. We have a 36 ft 10 ton /+ sailboat. A few years ago we were some 60 miles off shore the USA and when the crankshaft said 'howzit' and broke in half, we put our 10 hp outboard onto the bracket on the stern. got back to FT Lauderdale sailing or motoring then up the ICW to Jacksonville with the out board only. So if dis-assembly and cleaning etc doesn't work I suggest the cheapest option would be to get a s/h 10hp o/b and for your friends limited need that should suffice
 
Boat sank and stayed down for a month - as far as the engine is concerned - so what? It certainly isn't a write-off. Like the man says, remove injectors, as two or more valves were likely to have been partially or fully open and crank engine by hand to eject water. Put some oil down each hole to keep cylinder walls lubricated and replace injectors. Empty sump, suggest you flush that with parrafin before refilling, change all filters. It is highly unlikely water will have found it's way into the fuel system if it's a diesel as it is already full of diesel so that is not likely to cause a problem. If a petrol engine there's more work as that system will have to be cleaned out. Either way the fuel tanks will need to be emptied and flushed, diesel floats on water so that can be recovered and used once water is out of the tank. Electrics - silt will probably have found it's way into starter and alternator, solution I'd say is hose pipe, flush clean, airline to blow out the worst, and a day or so in a warm place to dry out. An oven very low heat would do the job. After that - check or refill batteries and off you go! Costs - very little really.
 
Looks like pretty negative response on electric propulsion. I'm sure you've checked out electricyacht.com where they claim success with a Cal 40 (15,500lb, that must be about 7 1/2 ton?).

I am considering tossing the diesel in my 36ft S&S in favour of an electric motor. She's not a heavy boat like yours. Power would be from shore power, a wind turbine and a generator. I recon with a gen set I might be able to fit air con as well but maybe that's a bit optimistic.

I haven't researched this much yet, I would be interested to hear from anyone who has used electric propulsion - is there anyone out there?

Cheers John
 
I can see two issues:
1) Energy storage. For even an hour's running, battery capacity needs to be quite serious.
2) Thrust. You don't need much power for cruising along at below hull speed, but starting, stopping, turning in a small space, preventing the windage on the bow from taking charge use a lot more power.
There have been many successfulelectric launches, but I don't think it's trivial to achieve.
The least aggro and surest low(ish) cost route will probably be to strip down the old engine and either recondition it or transfer the marinising components to a good used motor.
The other way to look at it is 'how would a new Beta (etc) improve the value of the boat?' The extra cost now may look cheap when you come to sell or after 10 years of owning something that is as it should be.
 
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