Petrol to diesel conversion, stay with me ....

[QBhoy]

That 2.5l BMW TD engine is used and abused in many applications...including being tasked with hauling the old range rovers about...and still are. The Range Rover usually falls to bits round about the engine !

 

[omega2]

That 2.5l BMW TD engine is used and abused in many applications...including being tasked with hauling the old range rovers about...and still are. The Range Rover usually falls to bits round about the engine !

Fair comment, read the thread I posted, I had a Vauxhall Omega 2.5 TD, BMW ENGINE AND AS YOU SAY it was bombproof. If that is now marinised then it should be fine. But avoid the VM DERIVATIVE.

Also you failed to mention the age and description of the engine you recommended.

 

[lambohill]

The Range Rover straight six diesel is prone to timing chain failure

 

[omega2]

As they stopped making those in 1989 I doubt that has anything to with Qboy's post about current BMW engines.
For what its worth I had BMW straight six petrol and BMW outdrive for 10 years (a 1989 boat) and it was easily the best outdrive and engine combination I have owned, although yes the diesel by VM were troublesome.

Your final comment "IS WHAT I AM TALKING ABOUT"

 

[Rusty1953]

Can anyone advise of a suitable Diesel engine to replace my old Volvo penta aq130 that would bolt straight onto a penta 270 outdrive. Any advice would be gratefully received.

 

[Assassin]

IMHO its a value issue.

You buy the new boat for 100k, fews years later its worth say 80K+ and you have used it loads with only minor issues hopefully.

You buy an older for 10k, pump 20-30k into it, have all the issues associated and time spent getting it right but still have an older boat worth say 15k.

Personally, i dont have the option of the 100k boat and most days enjoy the maintainence side so I'm in the do up club. I wouldnt however ever do a petrol to diesel conversion as the economies of scale just arent there

This is a quote which I agree and disagree with and understanding there are many factors at play here is crucial and the first is ability closely followed by contacts and availability, and finally your objectives.

In reality it comes down to what you can get at what price and what work you can do yourself as anything marked as marine is expensive and if you can get a solid hull which has been well maintained and fit your own engine you will be making immense savings on labour costs alone and labour is expensive as good marine engineers charge due to being in high demand, but can save you money through this experience.

 

[BruceK]

I could not have afforded boating if I hadn't done this. Admittedly I bought a raggety old boat with sound diesels already in. They had been completely dealer rebuilt. But the rest of the boat was a sorry state. I have pumped a lot of money into her bringing her back to her former glory not least of which was rectifying and overhauling drives and electrics. But she is now a fine vessel fully refitted, with a gradual and complete replacement of all carpets, drapes, vinyls, canvas etc including new paint striping and detailing. She was revalued and surprisingly I have lost little in the way of the refit so would recoup most of what I spent fixing her up. Using a generous helping of man-maths I am only 25k under which equates to 5k a year cost of ownership less fuel and berthing fees for the 5 years I've had her and that with any luck should now tail off as the boat is where it should be.
Fixing old boats isn't for everyone though, mine has given me a lot of grief over the long winters fixing it all up, constantly fettling and fine tuning and tearing my hair out because every job takes 5 times as long as you budgeted for it. But we are out all season right alongside all the new boats that never give problems but cost their owners a helluva lot more. Horses for courses I suppose.

 

[Divemaster1]

Saga 26 HT may be an alternative for you ... Scandinavian build, Usually Diesel .... on shafts etc., but will not satisfy you if you are after performance ....

https://www.nya.co.uk/boats-for-sale/saga-26-ht/

 

[moresparks]

I wonder if the "man maths " today add up in comparison to just a few years ago.
I have a twin petrol sportsboat and although I would have preferred diesels at the time, in the sub 30 foot cruiser market they were rare and expensive. Now look at today... the tide has turned against diesel fuel, Forecourt pump prices are up to 10p a litre dearer for diesel and goverments are just itching to seek ways to progresively increase taxes further.
Looking at reports at say a 28 foot single engine diesel semi displacement suggests around 2 MPG, I get that at cruising speeds of say 22 knots. Sure If I increase the loudness control to 11 my fuel consumption wil increase!!!!
So is it all now worth it - who knows what the costs will be in a few years time.
O/K I know about safety issues, 60/40 split and availability of petrol which alone will persuade many. But more and more new boats in the sub 30 foot market are going for high powered outboards so maybe availability will improve.
Now just got to look out for a sub 30 foot twin shaft drive hardtop with around 4 mpg in my price range as my next boat!.

 

[BruceK]

Semi displacements are dearer on fuel if you give them welly. In my 34 foot, 8 ton twin diesel sports cruiser I am averaging 2.2 litre per nautical mile or 1.1 litre per engine with a split of 2/3rd planing speed and 1/3rd displacement. Planing speeds being at circa 3k rpm (3.9 WOT on KAD 42's) and 23knts through water. This is for a fully bunkered boat carrying 4 for weekends out.
Friends Regal 28 on a single KAD 32 gets much the same at ~1 litre per nm and never gives it anything but full throttle.
This is the same sort of consumption I was getting on a Merc 3.0GL in a 19 foot speedboat. I know the latest outboards are remarkably economical but for inboards I just cant see there ever being a fuel equivalency. This affects range as well. My boat was originally designed with big petrol V8's in mind. As a result my fuel tanks are enormous by comparison giving me nearly double the range of my fellow boaters on diesels. Apart from being a nice extra for me now it just highlights how much more petrol the big V8's would have needed.

 

[Cavalierbond]

Sorry to tack onto this .. but am toying with but a 32 ft cruiser with two. Volvo 5.7 .. but am out off by the size of the engines .. what approx cost do you reckon to put two recon diesels in .. and would a shop take the old petrols in trade .. thanks

 

[BruceK]

Sorry to tack onto this .. but am toying with but a 32 ft cruiser with two. Volvo 5.7 .. but am out off by the size of the engines .. what approx cost do you reckon to put two recon diesels in .. and would a shop take the old petrols in trade .. thanks

Dont jump to the diesel horse just yet. You may soon regret it. Given the choice in hindsight I'd have preferred my boat to have the big petrol V8's in her were it not for the scarcity of petrol in my neck of the woods

 

[julians]

Dont jump to the diesel horse just yet. You may soon regret it. Given the choice in hindsight I'd have preferred my boat to have the big petrol V8's in her were it not for the scarcity of petrol in my neck of the woods

Why's that? Simplicity/Less to go wrong?

 

[BruceK]

In that size boat better performance by far and diesel could very soon be more expensive at the quay than petrol. It is on the forecourts and if white diesel goes through replacing red as on the books........ thCavelierbond will be kicking his heels

 

[julians]

In that size boat better performance by far and diesel could very soon be more expensive at the quay than petrol. It is on the forecourts and if white diesel goes through replacing red as on the books........ thCavelierbond will be kicking his heels

Diesel could be more expensive than petrol, but its unlikely diesel would become so much more expensive than petrol that it ends up costing more per mile, given how much more efficient diesels are compared to petrol. Isn't it?

I think there definitely a simplicity advantage to petrol, ie no turbos, no superchargers, no expensive mega high pressure fuel pumps etc, but not sure theres much of a performance advantage for normal boats with normal power.

I had a 21 foot boat with a 5 litre v8 mpi petrol at 260hp, then I swapped to a heavier 25 foot boat with a 3.6 litre 4cyl 260hp diesel. Top speed of the diesel boat is 23-4 knots lower than the smaller boat with the petrol, but the acceleration is similar. the fuel economy of the diesel is fantastic compared to the petrol though.

 

[BruceK]

If your petrol engine power is marginal then yes. But if you're not labouring a big V8 then the fuel usage is far more palatable. Your old V8 was probably also a carb version which wouldnt have helped. Not that petrol will be more fuel efficient but could be equivalent on the sum of total costs.
As for power and power to weight mine came with twin diesel 230 hp as the biggest they could fit. Good for 30 knts. Then the petrol variants up to 350 hp, not only lighter but that could damn near double that speed (460 total vs 700) . If I was to re engine now, petrol would be a very serious contender if not no brainer.

 

[julians]

Your old V8 was probably also a carb version which wouldnt have helped.

It wasn't, it was the fuel injected mpi version. The fuel costs of a 30+ foot boat with twin petrol will be horrific imo. Petrol are OK in smaller boats, but once you go up to a size where twin engines are required I'd have thought thst deisel would make more overall sense.

anyway back to the op question. I cant imagine it will be economically viable to swap to diesel, prob easier to buy diesel if that's what you want.

 

[BruceK]

According to www.boat-fuel-economy.com the difference at WOT between a V8 220 TKS and Penta 260 D4 as 15.9 gph vs 11.4 gph but 8.3 vs 7.4 at cruise revs. Hardly enough to make much difference when maintenance and repair bills start knocking

 

[julians]

My old 5.0 v8 mpi 260hp used to burn 35 litres per hour at 25knots, my current boat, volvo d4 260, burns 25 litres per hour at the same speed. So that's 10 litres per hour more, that about £13 per hour more at road fuel prices. So £26 per hour more for twin engines. Over a 100 hour season thats an extra 2600 quid on fuel. I guess if you don't do many hours then it's not a big deal.

 

[BruceK]

Me? No Im a marina queen, never go out. Fuel costs too much. :encouragement:
Now for maintenace and repair costs.... that 2.6k slims down some. If it hasnt for you, its just on back order