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Diesel powered pumps

Hi all, anybody got any thoughts on using diesel motors on dredges?
Im looking at a diesel to run a 5". Dredging around 4-5 metres down.
Any advice or thoughts would be great.

whats wrong with the standard petrol engine?

Diesels are quite a bit bigger and heavier for equivilent horsepower and for a 5inch it wouldnt pay for itself in fuel cost savings.
if its because of power at that depth youd be better off to add an extra pump with a booster jet half way down the hose but even then any half decent dredge should still have good power at 4-5m.

Hi
We run 2 diesels on out 6" with p500
Cheap as chips to run

For any of you commercial / serious dredgers running petrol engines, it might be worth your while claiming back the excise duty on the petrol you use.

Of the $2.30 per litre you pay at the petrol station, approx 70c goes to the government to pay for roads etc. Your gold dredge isn’t a vehicle so you can claim it back.

https://www.nzta.govt.nz/vehicles/licensing-rego/road-user-charges/ruc-rates-and-transaction-fees/excise-duty-refunds/

As long as you have your receipts etc, its pretty straight forward.

2 Likes

what hp are they i have been thinking about doing the same and what make are you using liters per hour to thanks for any advice

65c per litre rebate. on the farm we buy bulk and with the rebate theres only a few cents between petrol and diesel.

even paying townie prices for fuel I really dont see the point in changing to diesel to save a few bux a day if youre a rec dredger.
if its more then a hobby and youre burning thousands of dollars fuel you should be gst registered and paying income tax (gold gst exempt so none to pay unless other income source)

Diesel 8 hrs 8lt
Petrol 8hrs 15lt
Same hp pumps
Math is easy
Does depend on how much usage for us we are dredging 2/3 days a week for 6 month.
Price diesel to petrol motors buying was 600$
So for us there was a easy fuel saving cost
Hope this helps

20bux a day not really a gamechanger tho, maybe if new build dredge or a motor blows but not really worth the effort just to do randomly.

guess this is a forum of tight arse scrouge mcducks tho :slight_smile: what more could one expect. just out of intrest do they perform the same? Rpm, power etc

I’m working 4/5 days a week for 6 months. Seems a no brainer to me. diesel it is.
Seems I must be a tight arse scrooge. Or I just don’t like chucking money away.

Mostly it’s the weight issue for me iv been wanting to go diesel but not many options under 150kg most stationary engines are around 250-300 kg for a 40-50 hp engine then by the time a sub frame is made & pump housing the cost doesn’t seem worth it for smaller dredges mite be ok but for example a 5-6 inch Keene likely wouldn’t handle the extra weight of a diesel engine(s) unless you added more floatation.

Need a bit more info on what sort of pumps and compressor your running and is this a dual pump setup. Do you need to breakdown dredge also are you working at altitude and do you need the ability to get extra suck in the deeper holes?

Diesel kills it in the high hp 8 inch dredge applications generally (40+hp)

Actually something else I discovered in my diesel quest is not the Hp but the Torque some of these engines don’t have a high Hp or revs but high in Torque which is really the driving power .

I was looking to use a 12hp diesel on the 5", unsure of pump at the moment.
Compressor is a Keene KAC1. Working at 5m above sea level.
A mate uses a 12hp diesel on a 6", no compressor & it does struggle below 3m down.
But 5 litres of diesel Vs 20l petrol got me wondering if I should convert.
The diesel inc pump weighs about 70kg.

I’m working 4-5 deep. Its a bit of cash to convert so I don’t want to screw it up!.

70 Kg for a pump and engine for a 5 inch dredge is pretty bloody heavy. For a 5 inch id be running a petrol setup the extra cost involved with converting to diesel is not going to realize the savings in fuel. You also have to factor in increased servicing costs for oils and filters and the need to ensure fuel is very clean for a diesel setup. For small stationary engines reliability and ability to do repairs in the bush is important. Petrol engine are a lot easier to work on and maintain and parts are easier to procure.

The other point to bear in mind is a petrol engine can more easily be modded to increase power so if you need to get into those deeper holes running them at higher rpm is easier. There is also a lot you can do to a petrol engine that makes them a lot more fuel efficient for a cheap price. Happy to give away my secrets about this

HP is a function of torque x rpm divided by a value co-effecient. For a pump you need HP as it is a measure of work done over time.
2 pumps run at the same rpm but with differing torque values will have exactly the same suck

All I have to say is… Diesel. Have you ever spilt that shit on you. Its impossible to wash off. And all you can smell all day is Diesel. And you want to gold mine with it. On a small dredge. If you could stand on it to re fuel you might be alright. But it’s only a 5. So you remove your portability right away and to add a stinky, dirty, smelly diesel. Just the thought of a diesel dredge would make me not want to go near it. If you have a Honda motor, your fuel savings on a diesel will be paid for by going Honda. You don’t even have to factor in oil and filter. It’s a Honda. Drop it in the water, turn up side down, dry spark plug, pull cord, dredge. Bet you could never do that with a diesel.

I run dual 6.5hp Honda’s on a 5inch. Average about 1L each and hour. So let’s say $5 an hour. If your only getting 1 gram and hour at $50/g. Your fuel cost is 10% of your earning. Find any other “business” that makes 90% profit, and I’ll invest.

4 Likes

All good valid points, thanks.

I run a similar setup but on a 6" , two 6.5 Honda’s uses around $20 gas a day wouldn’t bother changing that setup as you pointed out it gets to a stage where your loosing the portability & seen as how a lot of us are solo it,s rather important to be able to move the dredge by your self .