Swapping diesel engine for petrol

[MarkHez]

The Perkins 4cyl diesel in my Creighton has packed up (suspected fuel pump), due to it being a large engine in a small engine bay, it's bloody awkward to work on and it looks like im going to have to lift the engine out to do the pump.

 

This got me thinking - maintenance on the engine is damn near impossible, and firing up a 40hp engine to move at 4mph seems a ridiculous waste of a big engine, so why not replace the engine with a 13hp single cylinder petrol honda general purpose engine? Transmission would be through twin A section V belts onto the current velvet drive gearbox. I'd be using a 4 groove pulley at the engine end, and should be able to run a 100A alternator at the same time as propulsion, but use an idller pulley to take tension off the alternator if required. The 4th groove on the pulley would be a spare, possibly used to run a pressure washer/water pump/second alternator through a similar tensioning clutch.

 

The engine could be lifted out and worked on by me on my own, it would free up a large space in the engine bay (to store coal, with a shovel hatch inside the front cabin) and it opens up easy opportunities for engine swaps in the future and would also allow me to use my 5.5hp genset engine (that has spare pulley grooves) to propel the boat in an emergency, i could easily make it up to be swapped in under 20mins.

 

Is there any reason that the BSS won't allow me a fuel swap? Can anyone think of any reasons why my plan wouldn't work?

 

Cheers for any advice

 

Mark

Edited January 16, 2015 by MarkHez

[Robbo]

Keep to diesel, it's safer and cheaper to run. The size of the engine (with in reason) doesn't really make much of a difference in the fuel consumption.

[Naughty Cal]

Keep it diesel.

[John Williamson 1955]

You may have problems with getting the revs right for best efficiency with the petrol engine, as they tend to need to run faster than diesels. They also use more fuel per horsepower hour.

 

Other than cost, is there any reason you're not considering one of the smaller diesels? They start at £250 on Fleabay at the moment.

[GUMPY]

One thing to be wary of is the frigde, gas fridges are a no no with petrol.

You will need to fit a bilge blower to evacuate amy fumes frpm the bilges before you start and for 15mins after you stop the engine. Also you will need better breathers on the tank vents.

There is more but that's all I can think of at present

[MarkHez]

You may have problems with getting the revs right for best efficiency with the petrol engine, as they tend to need to run faster than diesels. They also use more fuel per horsepower hour.

 

Other than cost, is there any reason you're not considering one of the smaller diesels? They start at £250 on Fleabay at the moment.

 

Hence using a Vee belt transmission from the engine - can easily downgear it.

 

I can't see any diesels around the 10hp mark for anything close to £250, my expertise also lies in petrol engine not diesel injection. Not that I cant teach myself, but it just makes things simpler.

 

One thing to be wary of is the frigde, gas fridges are a no no with petrol.

You will need to fit a bilge blower to evacuate amy fumes frpm the bilges before you start and for 15mins after you stop the engine. Also you will need better breathers on the tank vents.

There is more but that's all I can think of at present

 

Aiming for negative pressure on the engine bay using fans to clear the fumes and aid the engine in cooling.

[ditchcrawler]

 

Hence using a Vee belt transmission from the engine - can easily downgear it.

 

I can't see any diesels around the 10hp mark for anything close to £250, my expertise also lies in petrol engine not diesel injection. Not that I cant teach myself, but it just makes things simpler.

 

 

Aiming for negative pressure on the engine bay using fans to clear the fumes and aid the engine in cooling.

Positive unless its an ignition proof fan. blow clean air in not suck petrol fumes out

[NB Alnwick]

A diesel engine is generally far better suited to boat use for many reasons. Have you costed out the the repairs in terms of parts and labour. I would expect that it will be cheaper to repair your existing engine than replace it.

[MarkHez]

A diesel engine is generally far better suited to boat use for many reasons. Have you costed out the the repairs in terms of parts and labour. I would expect that it will be cheaper to repair your existing engine than replace it.

 

£400 to get the pump refurbed, £300 for a 13hp honda + pulleys etc, comes to about £400 and it makes it a damn sight simpler to work on in future. For negative pressure I'd use an engine driven fan instead of electrical.

[Guest]

 

£400 to get the pump refurbed, £300 for a 13hp honda + pulleys etc, comes to about £400 and it makes it a damn sight simpler to work on in future. For negative pressure I'd use an engine driven fan instead of electrical.

Somebody will hopefully correct me if wrong, but I think you should vent the bilges before firing the engine up.

 

If I understand the proposed gearbox drive with belts correctly, would this not put undue side load on the gearbox input shaft? Just a thought.

Edited January 16, 2015 by Guest

[cereal tiller]

Somebody will hopefully correct me if wrong, but I think you should vent the bilges before firing the engine up.

 

If I understand the proposed gearbox drive with belts correctly, would this not put undue side load on the gearbox input shaft? Just a thought.

Yes,the Gearbox input Shaft should be protected by a pair of chunky bearings with the driven pulley(s) placed between them.

 

Another engine option would be a single cylinder air cooled Diesel,many available at reasonable cost,Exhaust would be noisy and need to be insulated and protected from excess vibration.

 

CT

[MarkHez]

Yes,the Gearbox input Shaft should be protected by a pair of chunky bearings with the driven pulley(s) placed between them.

 

Another engine option would be a single cylinder air cooled Diesel,many available at reasonable cost,Exhaust would be noisy and need to be insulated and protected from excess vibration.

 

CT

 

Good thinking, hadn't thought about that, wouldn't be too hard to mount the shaft in a bearing, but it has got me onto the idea of lister single diesels, they're simple enough for me to get my head round!

[ditchcrawler]

 

£400 to get the pump refurbed, £300 for a 13hp honda + pulleys etc, comes to about £400 and it makes it a damn sight simpler to work on in future. For negative pressure I'd use an engine driven fan instead of electrical.

You really need to ventilate the bilge both before and after starting the engine, but you seem determind to go down this road regardless of what is said here so good luck with the project. By the way I am an old Norfolk Boy and am old enough to remember Broads Cruisers going up when the engine was started.

[Kieron G]

Diesel is King. I would save up and get the perkins repaired , without a doubt.

[craftycarper]

I never bought a creigton for the very reason you say that ridiculous great landrover engine under the cockpit floor was almost un maintainable unless you can do an unassisted handstand whilst hands free, plus the lack of conversation whilst driving because you could,nt hear anyone speak, most of the people on here have narrowboats so the engine is outback under the deck and not in the middle of the boat between bedroom and lounge, will also say the fact that petrol is between ten and twenty pence a litre cheaper than derv and honda engines are brilliantly efficient the running cost of a monster ancient diesel and a modern efficient jap petrol is negligible especially as you are only moving around 3 ton as apposed to 12-15 tons , so I would say go for it and if that fails stick an outboard on it and be done, don't know if you have a 26 or 32 but on my 34ft centre cockpit I get through a maximum of three litres an hour and that's on the severn pushing against a strong current

[Alan de Enfield]

Petrol availability on the canal system is not particularly widespread, you may need to moor and walk to a petrol station to 'top-up'.

 

Have a look at your proposed cruising area and see how available petrol is.

 

I have a small 3 cylinder Yanmar diesel (about 18hp I think) with very low hours that I took out of a ride-on lawnmower.

It would need marinising but the price will be 'right'. (It'll be less than the Honda)

If interested send me a message and I'll dig into the shed, get it out, and get more details and a pic or two.

[Bee]

Would the Honda cope with the existing propeller? No idea what prop. is fitted but I would think it could be a problem matching the different power / rev bands of the very different engines.

[John Williamson 1955]

 

£400 to get the pump refurbed, £300 for a 13hp honda + pulleys etc, comes to about £400 and it makes it a damn sight simpler to work on in future. For negative pressure I'd use an engine driven fan instead of electrical.

Normal practice is to run the bilge blower for some time before and after the engine is running to clear any fumes, which an engine driven fan can't do. You also need to sort out the little details such as a carburettor tray to catch any petrol leaks. You will also need to revise your fuel storage, with either an outboard tank or a bunded tank with a bund which drains overboard. the costs of installing all this may make it cheaper to buy a second hand diesel setup or think about ways to improve your current setup. From the installation requirements of the Boat Safety Scheme:-

 

"Petrol can overflow as a result of a flooded carburettor, and this means there's a danger of petrol leaking onto a hot engine or exhaust and potentially starting a fire or causing an explosion. To reduce this risk, carburettors (apart from the down draught type) must be fitted so that they allow any overflow to drain into a spirit-tight metal drip-tray.

The top of the tray has to be covered with a flame arresting mesh, made of copper or brass gauze, which is soldered to the rim of the tray. The tray must be removable or fitted with a fuel cock for emptying. A flame trap or air filter must be fitted to the air intake of petrol, petroil and paraffin engines. This will help to intercept flames produced as a result of an engine backfire. [2.19]"

 

When I bought this boat, I considered installing or using the small petrol generator which came with her while cruising, but the rules for installing it were so strict, I decided an inverter was the way to go. I would have needed the equivalent of a second gas locker just to store it, and to run it on board needed a sufficiently ventilated space completely sealed off from the rest of the boat. Just running it on the back deck would not be acceptable.The generator is still sitting in my mobile shed if anyone wants it.

Edited January 16, 2015 by John Williamson 1955

[Murflynn]

there are many good reasons why diesel engines are almost universal in boats of all types these days.

 

if you go back 50 years petrol engines were the norm, in small cruisers, open launches and speedboats, but lessons were learned and diesels became the norm.

 

............. don't even think about petrol unless it's an outboard mounted on the transom.

[Arthur Brown]

The cost of the BSS compliance conversions will greatly exceed any possible savings fitting a petrol engine. Petrol is hard to find on or near the cut but diesel is retail at marinas and lots of other boaty places and available from travelling fuel boats.

 

Petrol is best kept in a basket off the stern by an outboard motor if you must. Cycling to a petrol station with two plastic 5l fuel cans can't be fun either.

[Neil Smith]

Petrol availability on the canal system is not particularly widespread, you may need to moor and walk to a petrol station to 'top-up'.

 

Have a look at your proposed cruising area and see how available petrol is.

 

I have a small 3 cylinder Yanmar diesel (about 18hp I think) with very low hours that I took out of a ride-on lawnmower.

It would need marinising but the price will be 'right'. (It'll be less than the Honda)

If interested send me a message and I'll dig into the shed, get it out, and get more details and a pic or two.

Hi Alan, My mate could be interested in your yanmar, could you get the model no and year and pm me with how much you want for it.

 

Thanks Neil

[Alan de Enfield]

Neil - PM sent