How longs a piece of string question : Volvo Penta TAMD41 inu dp 90 fuel consumption

Found another HSO 30 .......

  • Length: 9.25 meters.
  • Beam: 3.25 meters.
  • Draft: 0.90 meters.
  • Bridge Clearance Height: 3.90 meters.
  • Displacement: 4,000 kg.
  • Material: GRPM (Glass Reinforced Plastic).
  • Engine: Volvo Penta KAD 42 (1 x 200 HP / 147 kW).
  • Fuel Type: 350 liters Diesel.
  • Engine Hours: 890 hours.
  • Propulsion: Sterndrive.
  • Cabins: 2.
  • Beds: 5.
  • Bathrooms: 1.
  • Fresh Water Tank: 150 liters.
Seems the 200hp option is the one ...

At 4MT displacement .... that puts her over the legal towing weight for the RR ... even though the RR is rated to snatch load of 7MT. So launch and recover is fine .. but not road travel.
 
ylop said:
So I asked ChatGPT the following question:

What would you expect the fuel consumption to be on this boat? Motorbåt HSÖ 30 1981 säljes på Gotland | Blocket

I thought that is a good test of intelligence - can it work out the link is about the boat, can it find the engine in the spec, can it then tell me a sensible answer.

It answered in Swedish! Now that makes sense to the extent that the website was .se but I asked my question in English. The answer does appear to be discussing fuel consumption. So I asked for an answer in English…

It does give values which seem sensible in a neat little table. It then goes on to explain the working like a diligent student. It slightly oddly begins by discussing the number of pounds of fuel it would use, then calculating the number of gallons (they are US gallons although an intelligent system would know I was in the UK so use appropriate units!). It does explain that Volva Penta TMD41 uses 0.4 pounds of diesel per horsepower per hour.

I suspect that number is a generic value for all diesels rather than specific to the TMD41.

So I asked it:

Can you tell me where you found the 0.4 pounds/hr/HP for this engine and how does it compare to other models?

And it replied:

This figure is a general benchmark used in marine diesel engine performance calculations. Specifically:
  • 0.4 pounds of fuel per horsepower per hour (lbs/hp/hr) is a typical Brake Specific Fuel Consumption (BSFC) value for older, naturally aspirated or early turbocharged diesel marine engines running at or near peak efficiency.
It’s not specific to the Volvo Penta TMD41, but it’s a reasonable average used when exact BSFC data is not published by the manufacturer.
…
…

And then provided more rule of thumb data and waffle about why fuel efficiency wasn’t the be all and end all but then, and this bit really makes me laugh it finishes off with:

If you’re looking for real-world numbers, you could:
  • Look up the Volvo Penta TMD41 workshop manual (some versions include fuel consumption tables).
  • Ask owners in boating forums like Boatdiesel.com or MarinForum.se.
  • Install a fuel flow meter (e.g., NMEA 2000 system) for precise measurement onboard.
Whilst some people use AI like a search engine, you need to be careful. Large Language Models like ChatGPT are not actually as intelligent as the seem. The use statistics to guess what the most likely words are in the answer but that doesn’t necessarily mean that everything written comes from the same source or belong to be combined together. It is not truely intelligent, it doesn’t learn from its mistakes. It bears a lot of resemblance to a politician - it will provide a long confident answer to a question, which if you know no different might make you sure they know what they are talking about. But if you know which questions to probe with might suddenly seem flimsy. It might even “accept” its answer was not what you wanted and give a better one. But Ask it the same question the following day and you’ll likely get some variation of the partly line.
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One thing you didn't get from AI, but you will get from this internet forum, the TMD41 statement in the advert is almost certainly an error. It would be highly unlikely that any manufacturer would fit a 150HP engine to such a boat, i'll bet it had the TAMD41 @ 200HP and even that will be underpowered.
 
PaulRainbow said:
One thing you didn't get from AI, but you will get from this internet forum, the TMD41 statement in the advert is almost certainly an error. It would be highly unlikely that any manufacturer would fit a 150HP engine to such a boat, i'll bet it had the TAMD41 @ 200HP and even that will be underpowered.
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Interestingly ChatGPT based its sums on 200Hp however if I understood the advert correctly it is a 1980s boat reengined in 2006 so depends what the owner was trying to achieve.
 
ylop said:
Interestingly ChatGPT based its sums on 200Hp however if I understood the advert correctly it is a 1980s boat reengined in 2006 so depends what the owner was trying to achieve.
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I missed that it has been re-engined. If it was fitted with a 150HP engine i'd run away.
 
The tamd41 ceased production in the early nineties which is what alerted me to query the engine type. we get 22 knots absolute max on our 9m Nimbus with a semi displacement hull and tamd41a and its design displacement is 3500kg.
 
ylop said:
However VP usually do provide fuel consumption data in terms of L/h at particular revs - eg is this the engine you have? http://goldcoastpower.com/brochures/VOLVO TAMD41M Brochure Specifications.pdf
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No it doesn't. It provides fuel consumption at particular loads.

What load your engine is under at particular revs will spend on whether it is in gear, and if it is in gear by (b) your particular boat, and (b) the weather, wave etc. conditions and any hull and prop fouling.

Your engine control level doesn't control the amount of fuel going into the engine, it sets the revs. The governor automatically delivers as much or as little fuel required to first reach and then maintain those revs.
 
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colhel said:
The tamd41 ceased production in the early nineties which is what alerted me to query the engine type. we get 22 knots absolute max on our 9m Nimbus with a semi displacement hull and tamd41a and its design displacement is 3500kg.
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TAMD41 engines were still being made until 2005 I believe.

My 760 built in 2005 has a 200hp TAMD41p and consumption appears to be about 24l an hour at 16knts doing 3200rpm if that helps.
 
On the subject of AI, I have just spelt a fruitless 30 minutes trying to find out using AI.Where on earth the coolant drain plug is on the starboard side of my tamd 41 because i'm scuppered if Ihear find it. Contributors to this topic may be pleased to know that AI was absolutely 0 use - if any of you reading this could help me by telling me what it's next to that would be most helpful as I'm pulling my hair out !
 
LittleSister said:
No it doesn't. It provides fuel consumption at particular loads.
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Yes , but assuming you have props that make the engine reach the same rpm,s at wot , the published propeller load curve will fairly closely fit at any boat installed , a heavy semi planing hull as well a light full planing hull .

The load at lets say 3000 will be similar and so the fuel flow in ltr/h in both applications , the difference is that the light boat uses a way higher pitch prop and travels at 3000 a lot faster .
 
Under - Over powered .... IMHO - these depend on the intended use of the boat.

For me - such a boat IF I BUY .... would spend 90% of its time on the river with general speed limit of 8kts in lower reaches in / near Port and in upper reaches - with care to respect other users and people fishing from dinghys etc.
 
Refueler said:
Under - Over powered .... IMHO - these depend on the intended use of the boat.

For me - such a boat IF I BUY .... would spend 90% of its time on the river with general speed limit of 8kts in lower reaches in / near Port and in upper reaches - with care to respect other users and people fishing from dinghys etc.
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But, if it's been re-engined (as someone suggested) with a 150HP TMD41 it isn't likely to get on the plane, so you may as well rip the engine out and fit an outboard to push it around at 8 kts.
 
Loggo said:
On the subject of AI, I have just spelt a fruitless 30 minutes trying to find out using AI.Where on earth the coolant drain plug is on the starboard side of my tamd 41 because i'm scuppered if Ihear find it. Contributors to this topic may be pleased to know that AI was absolutely 0 use - if any of you reading this could help me by telling me what it's next to that would be most helpful as I'm pulling my hair out !
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this may help, picture top-left Page2.png
 
LittleSister said:
No it doesn't. It provides fuel consumption at particular loads.

What load your engine is under at particular revs will spend on whether it is in gear, and if it is in gear by (b) your particular boat, and (b) the weather, wave etc. conditions and any hull and prop fouling.

Your engine control level doesn't control the amount of fuel going into the engine, it sets the revs. The governor automatically delivers as much or as little fuel required to first reach and then maintain those revs.
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Did you open the link? It provides consumption at different revs for two different load conditions - one max load and one a theoretical prop. Essentially a good working asssumption would be that the consumption is somewhere between the two. But worst case no worse than the max load the provide.

I don’t think refuelled is trying to work out his expected consumption to the nearest mL - he just wants to check that he’s not going to be burning ridiculous amounts of euros to go on a plod along the river.
 
ylop said:
Did you open the link? It provides consumption at different revs for two different load conditions - one max load and one a theoretical prop. Essentially a good working asssumption would be that the consumption is somewhere between the two. But worst case no worse than the max load the provide.

I don’t think refuelled is trying to work out his expected consumption to the nearest mL - he just wants to check that he’s not going to be burning ridiculous amounts of euros to go on a plod along the river.
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Yes, i did open the link. That's how I knew that the graph showed consumption against load, not revs. Volvo (and other engine manufacturers) don't know what load you're putting on the engine, and at cruising revs this will usually be way below the maximum load the engine can meet at any particular revs, and the consumption will only be that required to meet the load applied.

As a guide to fuel consumption, what others get with the same model boat with a diesel engine at a similar speed will be much better than peering at manufacturers graphs. Which diesel engine it is won't make a lot of difference.
 
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