Silette Sonic Outdrive.

[nebeluk]

Hi, has anyone experience with the Silette Sonic outdrives on smaller cats driven by a Vetus diesel inboard engine eg Prout 31. 8/9 meter Catalac, or 8m Heavenly Twins. Sailing solo so don't need a bigger boat. Or what is the thinking of a single outboard about 18hp for Coastal Cruising in the Mediterranean. I don't really care for the idea of petrol (gas) storage on-board, but if needs must

[smj]

We have owned a cat with a sonic drive coupled to a diesel and also a few cats with outboards. We would much rather have outboards as long as they are well placed on the boat. Gasoline on a boat is safe as long as it's stored in a vented exterior locker. Probably 90+% of the boats in the world are gasoline powered outboards and they have a great safety record.


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[valhalla360]

We have a Gemini which came with both options. Ours has a 25hp Fuel Injected Outboard.


From friends with the Stilette, we are glad we have the outboard. While it works OK, it requires religious maintenance. The main advantages:
- Hot water heating off the engine coolant.
- Big alternator to charge batteries (but with solar panels it's not really needed)
- Slightly better fuel economy (but 4 stroke engines have closed the gap to a large degree)


The fuel tanks are on the bridge deck and bottom vented to the water and the engine is completely clear of the hull. This addresses 99% of the concerns with having gasoline on board. The problems with gasoline in monohulls is because the fuel tanks are typically down in the hull and any leak will result in fumes in the bilge. This is why it is critical to run the blower on a gas powered boat (which is still safe if you follow proper procedures). With bottom vented tanks and outboard engine, this issue goes away.


The outboard starts quickly, is quiet and efficient. While it is electric start, it is still easily pull started in the event of a low battery. We replaced the old 2 stroke for $5k. That was entire new drivetrain fully installed. You will be lucky to get the diesel for that without installation. Anywhere you go on the water, there will be a guy who works on outboards. Get away from major marinas and marine diesel techs get a little harder to find and likely come at a higher hourly rate.


I wouldn't not get a boat with a stillette but given the choice, I would take the outboard.

[Pete7]

Those Sonic drives have been in production for years and there are thousands of little boats on the UK canals powered by them.

sonic_100_sterndrive

The problem I suspect is they don't get the maintenance that any drive needs, in fact probably no maintenance at all for years . If you can do this then the diesel engine has a number of advantages as stated above, plus diesel will be easier to obtain at the waters edge rather than trips ashore with cans for petrol.

Pete

[atoll]

Originally Posted by nebeluk

Hi, has anyone experience with the Silette Sonic outdrives on smaller cats driven by a Vetus diesel inboard engine eg Prout 31. 8/9 meter Catalac, or 8m Heavenly Twins. Sailing solo so don't need a bigger boat. Or what is the thinking of a single outboard about 18hp for Coastal Cruising in the Mediterranean. I don't really care for the idea of petrol (gas) storage on-board, but if needs must

the vetus,M3.10,M41.4 series were built by misubishi,reliable industrial engines easy, to get spares for in Europe from vetus.

the sonic drive is also robust and easy to get spares from Silette Marine Propulsion Systems

regular greasing and routine maintance should provide reliable service.
the leg is also steerable in fwd and reverse,for close quarters manovering,not as versatile as twin engines,but sufficient in most conditions.

earlier models had the gearbox in the leg so the leg needs to be dropped to run the engine,but the more common 1:1 drive uses a standard marine gearbox off the engine flywheel that allows battery charging with the leg lifted.

twin outboards,are generally lighter,but do suffer from issues with dirty/old fuel if not run regularly and cavitation at higher revs in rougher conditions.

on the prout fitting twin outboards would require significant modifications.

fitting a single steerable high thrust 18hp on the models you mentioned has been done with fairly good results,apart from some cavitation issues.

[valhalla360]

Originally Posted by atoll

regular greasing and routine maintance should provide reliable service.

Far less margin for error based on comparisons on the Geminis.

the leg is also steerable in fwd and reverse,for close quarters manovering,not as versatile as twin engines,but sufficient in most conditions.

Outboard provides similar benefits and I agree, it's almost as good as twin engines (but not quite).

earlier models had the gearbox in the leg so the leg needs to be dropped to run the engine,but the more common 1:1 drive uses a standard marine gearbox off the engine flywheel that allows battery charging with the leg lifted.

twin outboards,are generally lighter,but do suffer from issues with dirty/old fuel if not run regularly

Are you suggesting diesels like dirty/old fuel?

and cavitation at higher revs in rougher conditions.

Really not any more of an issue unless you put a shorter shaft outboard on. Assuming similar length leg in similar mounting position, no real difference.

on the prout fitting twin outboards would require significant modifications.

fitting a single steerable high thrust 18hp on the models you mentioned has been done with fairly good results,apart from some cavitation issues.

We know people who have switched to as low as 15hp but you are giving up capability when fighting a strong headwind or current. With 25hp, we have been flat out against a 35kt wind and were only making around 3kts. Not sure we would have made headway with 15hp (on the ICW so there were no waves).

[nebeluk]

thank you everyone for the input.....now just have to choose