Rib/engine advice

[John Kennett]

John

The Ribcraft should serve you well -- and you will certainly appreciate a diesel engine when it come to filling up!

What is the engine you are going for?

John

[Powerboat]

Hi John ,

As a Diver myself , I would be concerned about the intrusion on valuable deck space of an inboard diesel , especially on a relatively small dive boat ( 6.8M ).

Have you considered twin 4 strokes with underfloor tanks ? Twin 100 hp outboards would equate to a single 150hp .I have a Yamaha 100 hp 4 stroke behind one of Lough Ree Powerboat School's training craft ; a Lencraft Lynx 6.5M RIB . It has been terrific .One days hard driving training 3 students on an ISA / RYA Powerboat course costs only £IR12 ( £STG9 )in fuel .

I have two similar boats except with single 115hp Yamaha 2 strokes in the Army Boat Squad which use £IR70 per day during similar training . I am firmly convinced that 4 stroke is the way to go for cruising and dive RIBs . Great economy and great torque to get that load on the plane in the first place and not too heavy to tow . True , 4 strokes lack the 0 to 60 of a two stroke but who needs blistering acceleration in a dive boat ..

The only real advantage I can see for diesel these days is that diesel is more readily available around the coast than petrol (which is almost impossible to obtain around the Irish Coast as well as on the Shannon .)

Hope this is of help .

Best wishes,

Stuart


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[John Hayes]

My diving club is looking at purchasing a Ribcraft 6.8m with 170hp inboard diesel. We are drawn to diesel by fuel savings (as we will use the boat most weekends), reliability and it just falls within our budget. Be grateful if anyone has any knowledge of the boat and engine, its performance , reliability, servicing costs and whether you believe there is a better alternative.
Many thanks

[John Kennett]

Stuart

What are the prices for petrol vs diesel in Ireland these days? I know that petrol is cheaper than in the UK.

I absolutely don't agree that there is no cost advantage of diesel over petrol in the UK -- even if a four stroke outboard may do the same mpg as a diesel, the difference in price (30p/l for diesel, £1/l for petrol) makes a huge diffence.

John

[Powerboat]

Hi John ,

I never said that 4 stroke petrol is "more" economical in mpg than Diesel .

What I did say was that all things considered , ( economy , engine weight , ease of towing and intrusion into deck space ) that 4 stroke is in my opinion the best all around package for a dive boat.Twin engines give redundancy in the event of engine failure at sea and also make the craft very safe and easy to close quarter manouevre around divers in the water .Another often overlooked safety feature is that diesel engine throttle controls are usually not fitted with a safety lock for neutral . This safety feature is vital when you have divers in close proximity to a running engine . All it takes is one careless person aboard to knock against the morse lever to put the boat in gear and mince a diver .

Petrol over here is substantially dearer than in the UK .( although we still find it expensive ! )

For information , in Ireland , Petrol is about Stg0.58 perlitre and Diesel is about Stg0.50 per litre at forecourt pumps . Commercial tax free diesel which can be used in boats over here is about stg 0.32 per litre .These are very much worst scenario prices . The general trend at fore courts is that diesel has been gaining on Petrol and we expect that by next year there will be parity .

Best wishes ,

Stuart

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[John Hayes]

John, thanks for the reply. The power unit we are looking at for the 6.8m Ribcraft is a Volvo Penta KAD 32 DP diesel Inboard (170 hp) wih a duo prop stern drive. Towing is not really a issue for us as we have an Avon searider which we can easily tow and plan to use the diesel as a boat that with provide for local diving out of Brighton

[John Hayes]

Thanks for the reply Stuart

Ideally if funds were not an issue we would go for a large diesel but are budget at around £25k simply does not stretch to it. The issue of space in a diesel is one we have pondered for some time and our objective of carrying 8 divers offshore we think will be met by the Diesel

Its very interesting what you say on the fuel savings side as that aspect has been an important consideration for the club. Our generally held view was that four strokes would still be considerably more expensive than diesel engines to run - has there been any comparative studies undertaken does anyone know? The other consideration on 4 strokes is the reliability is we have heard is questionable particularly for the larger units - this I must add is in the main heresay and revolves around the cooling system - whay your view on this?. Again we felt a diesel would score much better.

Regards

John

[Powerboat]

Hi John ,

Quick correction first !

It will be obvious from the context of my last message that what I should have said is that Petrol is substantially " Cheaper " over here in Ireland ! I mistakenly typed "dearer" ( years of looking at you guys across the water drinking cheaper juice during the 70s and 80s ! )

On the subject of 4 stroke reliability - I only have my engine for about 4 or 5 months so it is probably too early to say .

However, In many years of experience I have generally found that most unreliability stories about Outboards of one make or another , Sterndrives , etc. originate because of poor or non existant routine servicing by the owner . I have owned or used 20 or 30 new engines of various makes and age in the last 10 years and have never had a problem with any of them . Why ? I like to think that it is regular maintenance and good driving habits .

On the whole diesel is going to be better on mpg especially on UK prices , however you must also consider the greater initial capital cost of the engine and the other factors we mentioned . There is also of course a price premium on 4 strokes .

For info , my own boat Ally Cat which you can see on our website www.powerboat.org cost about £stg 25k .This included LCD Radar , Gps colour plotter - sounder 4 seats , long range tanks a 2 wheel Rollercoaster with winc / brakes and a few other goodies . I have two sister ships of her fitted with dive racks instead of the extra seats with the Army Boat Squad . We reckon on carrying a Cox plus 4 divers on these 6.5 m boats equipped with Yamaha 115's

Feel free to contact me off list if you like .

Best wishes ,

Stuart


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[aladdin]

With regards to the inboard/outboard engine issue, I thought I would share my own experience with you.

My diving club has a 6.7m rib with an inboard petrol unit and forgeting the fuel discussion, the engine housing does nothing but get in the way! I have a 5.25m rib with twin outboards which has more deck space!

As a diver my advice would be to go with outboard and keep the space for the divers.

One further comment, please don't place the cylinder rack across the deck, place it bow to stern, not only does it prevent the coxwain accessing the rest of the craft but also causes back trouble when lifting cylinders over the rack.

good diving,
Kevin.

[gaelforce]

If I were you I would go for the more reliable inboard diesel engine. A possible solution to the space problem is to mix the divers up with 1 or 2 water-skiers. Water-skiers don't take up any space in the boat. Alternatively, some divers could volunteer to waterski to and from the dive site. Hope this helps!

[John Kennett]

If you do go for the diesel option, then a bench seat on the engine box can make good use of some of the space. Ribcraft do a lovely wraparound "bucket sofa" which is really comfortable!

John