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Author Topic: Good HP/ weight VW diesel for a jetboat project  (Read 959 times)

October 21, 2016, 04:03:28 pm


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Good HP/ weight VW diesel for a jetboat project
« on: October 21, 2016, 04:03:28 pm »
Hey guys

I am a marine engineer with mostly big diesel engine experience.
As a hobby project I would like to build an aluminum Ridged Inflatable Boat powered by a jet pump.

Since I'm using a jet pump I don't need a gearbox and I need approximately 100hp at 3500 - 4000 RPM
The engine will be fresh water cooled trough a tubes system welded to the inside of the aluminum hull.

What engine should I use?
The lower the weight the better.
It has to be easy available in Europe in case I blow one up.
If I use a modern common rail engine can I wire the ECU to normal boat controls (start switch, emergency off switch, hand throttle)

Thoughts about a car engine for marine use:
The engine will have far less running hours then in a car. maybe 100h a year.
It will be at a continuous high load.
It will have better cooling then in a car.
I will fit it with a water cooled air cooler thus air intake temperature after turbo will be less then 20C. Like in a marine engine.
It will never run high RPM unloaded.
It will experience higher G forces and running at an angles. Maybe I need a deep sump or a dry sump and separate oil tank. (I can try and see what the oil pressure does)

As to why? A 1.9TDI engine costs 3000 at the scrapyard. A 100hp marine engine weighs double and costs 15 000??
(It weighs double because of the gearbox and seawater cooling circuit I don't need)

Reply #1October 22, 2016, 04:15:02 pm


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Re: Good HP/ weight VW diesel for a jetboat project
« Reply #1 on: October 22, 2016, 04:15:02 pm »
An ALH would probably be the simplest way to go. Those were found in the Mk4 platform up until around 2004. They're simple, dependable and common. They put out 90 HP bone stock at around 4500 but that can be increased very easily.

I believe the ASV is around in Europe too, those were more like 110 HP stock.

Either of those engines can be run with or without the electronics. They are drive by wire in stock form - the accelerator pedal is connected to the ECU which in turn controls the injection pump. A Land Rover injection pump is nearly a direct bolt on and eliminates all the wiring.

Larger injector nozzles and a Land Rover pump would easily give you the power you are looking for. The stock turbos would work - they are variable vane turbos with ECU control but given your operating parameters just finding a good static point to set them would work fine.

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