Small diesel wing engine for 33ft motor boat

[blampied]

I'm toying with the idea of fitting a small diesel wing engine to my single engine (370hp Volvo) Aquastar motor boat.
We are living on the boat travelling around the western end of the Med (currently in Spain) but also includes slow canal and river use as we duck in and out of the French canal system. I am aware that using the main 370hp for long periods at or just above tick over (despite quick blasts when no ones about) is not ideal.
The Aquastar is semi displacement between 7.5 and 9 tons

Objectives:-
A get us home option if the main engine fails whilst at sea.
To be fitted with a large alternator for battery charging & to run through the inverter doing away with the genny
Allow us to travel at slow speed on the canals without constantly running the 370hp Volvo.

There looks to be easy installation access room in the lazerette

Looking for opinions on are my expectations realistic:-

What are the ball park costs likely to be for the motor and installation
What size hp motor should I be looking for? (I'm guessing about 30hp?)
Assume it will need to be a folding prop, would 2 blade do or would 3 blade be better, (smaller diameter closer to hull?)
As main motor is TAMD Volvo.
should I stick with looking for Volvo (D1-30 or similar)
i understand other makes can be cheaper? Cost would be a big decider.
As I'm in Spain (thinking about Cartagna for winter) I'm in no position don't have anything more than basic hand tools on board to do fitting an engine, so would need to be a boat yard job.
Any recomendations of a reputable boatyard in the area.

Thank you for looking.

 

[Monique]

It is doubtful a wing diesel engine would prove very beneficial. The boat will also get a list to the installed side etc.

Consider a 30 HP petrol outboard? Should be enough for pooling and charging batteries.. if you are frugal "leccy" wise.

GL

 

[Davy_S]

There was an article in PBO earlier this year (cant remember which month) I think it was a small Aquastar, he fitted a Beta engine around 14hp, it showed most of the detail and costs involved, sorry I cant be more helpful but a search will find it. The weight of the engine to one side can be offset by a fuel tank and battery on the other side with a bit of calculation.

 

[PCUK]

You'll need 30hp if it's going to get you home. I had a 30hp BMC 1.5 in my 14 ton steel flybridge. It gave 6 knots on a 3 blade folding prop'. The main engine at 300hp gave 12 knots. You could probably expect about 7.5 knots on your boat. Well worth the effort in my opinion having had experience of having a wing engine.

 

[Davy_S]

The article I mentioned was in the July 2015 PBO, the boat was a 27ft Aquastar, a beta 14 was fitted. the owner said it was well worth doing.

 

[Tranona]

D1 30 would be OK. You can get it with a down angle gearbox which might help the installation. The biggest amount of work will be building the engine beds and installing the stern tube and P bracket. Engine and box around £7.5k with a standard 115 amp alternator. Propeller (3 blade Flexofold) about £1200. Controls, shaft, exhaust, electrics around £1.5k materials plus independent fuel tank. 100l will give you around 50 hours motoring.

 

[Billjratt]

If you already have a generator would an electric drive be an option?

 

[William_H]

What a horrible idea IMHO fitting another diesel engine and prop. I think if you carefully maintain the main engine for reliability then it should be OK for long periods at low speed. If it does need dismantle and decoke etc then this will be cheaper than fitting anothe rengine. I might be wrong of course.
What might be practical is an electric motor to run off your generator that with gear box can be conected to drive the main prop.
good luck olewill

 

[duncan99210]

The best yard in Spain (imo) is in Sant Carles de la Rapita, between Valencia and Taragona. Well run yard and there are people there who can do GRP work and a Volvo Penta main agent. Not the cheapest but certainly one of the best run I've come across.

 

[fisherman]

We once entertained the idea of a low hp aux drive, and would have fitted a hydraulic, possibly multi belt drive, onto the main shaft. Our object was to be able to go really slowly. You would remove the belts for normal running. Gearbox must be able to freewheel. Could you use a stern drive on the wing, less work fitting and better for normal running.

 

[michael_w]

What about using a saildrive?

 

[blampied]

Thank you all for your replies, a lot of conflicting opinions.
It has given me a lot to think
I'm sure finding a Spanish boatyard that gives me confidence and a reasonable quote will be the deciding factor.

 

[PCUK]

What about using a saildrive?

That reminds me, A friend had main shaft drive and an outdrive for the wing. Worked fine but looked a bit odd.

 

[prv]

If you already have a generator would an electric drive be an option?

The problem is what you do about a propeller.

If the main engine is well maintained, then the disabling problem is just as likely to be damage or entanglement of the stern gear. Someone considering a wing engine is seriously concerned about reliability, which means a) the main engine will be well maintained and b) they don't want to take the chance on the prop and shaft.

So a wing engine really needs its own prop. A simple solution from an installation point of view is a saildrive - comes with its own beds ready to be trimmed and glassed into the hull, and the leg can protrude through the bottom without any building of stern tubes and P-brackets. Seems a bit inelegant to have a leg sticking out on one side, even with a folding prop, but I know it is done.

Pete

 

[Keith-i]

A small jet drive would be the most novel solution would it not?

 

[ianc1200]

Straight Across has had a wing engine from new in 1951; then a mk2 Morris Vedette as a wing engine, now a 8hp Yanmar 1GM which got us home when the 62hp Nanni destroyed itself. The Yanmar will push us along at just over 5kts in still water. It has it's own separate rudder but I have fixed it it the striaght ahead position. SA is 30' and 7.25 TM net about 5.25.

 

[pvb]

An outdrive would surely be the ideal transmission to use, as it can be steered easily. With a shaft drive or saildrive you'd need to install another rudder too.

 

[Davy_S]

An outdrive would surely be the ideal transmission to use, as it can be steered easily. With a shaft drive or saildrive you'd need to install another rudder too.

Why would you need another rudder? surely the main rudder would steer the boat.

 

[blampied]

Thank you all for your responses.
I haven't considered sail drives before but am now coming around to that suggestion.
Strange that the sail drive legs look to be so much longer than would be needed for the propellor to swing.
As ianc1200 mentions he has only 8hp auxiliary on a similar weight boat. I'm starting to think my original assumption of needing 30hp to be excessive.
I like the idea of Volvo D1 as they seam to have the biggest alternator 115amp compared to other makes, (maybe the D1-13 would be suitable)
one of the main uses I would be hoping to put the engine to would be as a generator, run through an inverter to power our air conditioning unit, as the air-con would need something like 90 amps at 12v I'm thinking that even a 115 amp alternator would only provide 115 for a peak of a few seconds and not be expected to provide it long term so overheat through running long term at close to capacity. I need to look at if bigger alternators (150 ish) are available to fit the D1 and if the small D1-13 is man enough to run such an alternator.

 

[pvb]

Why would you need another rudder? surely the main rudder would steer the boat.

For slow speed manoeuvring, prop wash over the rudder is important. If you don't have that, the boat won't be very controllable.