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

simonfraser

simonfraser

Well-Known Member
Joined
13 Mar 2004
Messages
7,609
Location
Outboards 4 mobo’s, unless you do a lot of miles
Visit site
I am still looking for a 26ft mobo, hard top, diesel, with a good rear seating area - some of facing towards the stern.
NO rear fishing area, plastic tub MF etc.

Not many about, the only ones i can see, Aquador 26 HT, are quite old.

So, just thinking, why not 'just' find an old petrol boat like the above, suggestions please, and re-engine it.
Yes that will take a lot of time / money, but a totally new Cancun 260 is 100k+ and has a fabric 'hard top'

Shoot me down.
 
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
 
Key issue for me is availability of fuel. If petrol is available in your chosen cruising area, don't write it off...if you are in a diesel-only area, then you have no choice. I re-engined my Fairline 21 with a Mercruiser petrol, but we have availability on the marina in SoF. Cost of a replacement Diesel engine would have made the project excessively expensive.
 
If you re engine with used engines would that be any different to buying an old diesel boat? If you are thinking new, I would think the cost wouldn't be far off a new boat anyway.
 
simonfraser said:
I am still looking for a 26ft mobo, hard top, diesel, with a good rear seating area - some

So, just thinking, why not 'just' find an old petrol boat .....
Click to expand...

And just use it.
IMHO with single engine under 28 ft, petrol is just fine, provided you can avail of it.
Over this size and two engines, diesel all the way.
The money you save will buy a lot of petrol.....
 
Suppose it depends on the boat you buy and if you are going to keep it for ever.
If you buy a petrol boat with an outdrive and convert to diesel, it can be an expensive excercise, depending on how you want it to perform.
Plenty of people get rid of the gm v6 and v8 petrols and stick transit engines in hem relatively cheaply, but they would only be suitable for river cruising.
Even if you were to replace with a more powerful diesel equal to the petrol...the chances are that you would need to change the outdrive ratio or buy a new outdrive. The gearing would not be suitable for the lower revving and different power curve of the diesel.
The exception to the rule here might be if you replace the petrol gm engine with a diesel gm, like a 6.2l or there is a chap in the north of England who specialises in replacing the gm petrols with the bullit proof BMW 6 cylinder engine, which actually has similar rev range to the gm petrols....all that said, this may not be the type of boat you are looking at.
If you are thinking of a hard top shaft drive, I've always wondered about the Arvor fishing derived boats. They seem quite affordable recently.
Perhaps worth noting....the petrols gm engines, especially the v6 4.3, are great things and aren't rediculous on fuel if used wisely. The cost of replacing this with a diesel would far out weigh what you would save on fuel by doing so. They save a fortune on service costs too. All service items are available from most motor factors are tiny costs. The later MPI gm engines are better on fuel again. My 5.0 MPI costs roughly a pound £ per mile at a cruising speed of 20mph and 2200 rpm. That's perhaps at the best end of the scale, being a light boat with a big engine, but you get the idea.
At the risk of droning on...a few years ago, my friend and I had similar boats (I had a Sealine 218 with 4.3 petrol and he had a cruisers 224 with a tamd31 diesel) with similar weight. The Sealine would perform brilliantly, refined, quiet and smooth at 20 knots cruising....his would be almost flat out at 20 knots and noisy, smelly and rattling. He used about the same quantity of fuel as I did. Fair enough the fuel was cheaper for him, but the extra 30-40p per litre was worth the refinement and general feel of the boat. Not to mention the bags of extra power I had in reserve !
Perhaps of no use to you at all, but just a general food for thought.
 
Forumite purchased a stereotypical small petrol powered boat with outdrive which had at some point had considerable amounts of time and money spent on on it by its mature and careful long term first owner.
The entire conversion was done using components from well known and respected marinising outfit on the South coast.
The result may well have extended the working life of the boat for a short period but afterwards was a catalogue of expensive and dispiriting disasters for its new owner.
In quick order everything that could fail did and of course the entire thing being a collection of custom modified components,almost every part was difficult to source and or replace.There are only so many times you can be towed back, once by a bright orange boat, before it dawns that it is time to unload the boat on some new unsuspecting owner.
 
Last edited:
oldgit said:
Forumite purchased a stereotypical small petrol powered boat with outdrive which had at some point had considerable amounts of time and money spent on on it by its mature and careful long term first owner.
The entire conversion was done using components from well known and respected marinising outfit on the South coast.
The result may well have extended the working life of the boat for a short period but afterwards was a catalogue of expensive and dispiriting disasters for its new owner.
In quick order everything that could fail did and of course the entire thing being a collection of custom modified components,almost every part was difficult to source and or replace.There are only so many times you can be towed back, once by a bright orange boat, before it dawns that it is time to unload the boat on some new unsuspecting owner.
Click to expand...

On the other hand, Neale stuck a KAD32 into a petrol Bayliner, and it worked well for several years.
 
FlowerPower said:
On the other hand, Neale stuck a KAD32 into a petrol Bayliner, and it worked well for several years.
Click to expand...

To be fair though, it did cost me more than the boat was worth :eek:

A professional conversion is a wonderful thing. But I can't see how it could ever be financially worth doing. I offset the cost by enjoying some serious extended cruising that I would never have done with the old V8 petrol. I also helped to justify it with some man maths, but i cant remember the exact equation I used now :D

Buy the boat with the right engine/s would be my advice. In the long run it will be cheaper.
 
I can never understand this obsession with costs. Power boating is a waste of money however you do it. So why worry about profit and loss? I have always built or rebuilt my own boats because in the end I get the boat I want regardless of cost, which has always worked out far cheaper then buying and selling production boats.
 
Omega 2
You will need to explain...why do you consider the straight 6 BMW turbo diesel as such ? Have you had a disaster with one ?
 
PCUK said:
I can never understand this obsession with costs. Power boating is a waste of money however you do it. So why worry about profit and loss? I have always built or rebuilt my own boats because in the end I get the boat I want regardless of cost, which has always worked out far cheaper then buying and selling production boats.
Click to expand...

Time? ......Boating vs Fiddling :)
 
QBhoy said:
Omega 2
You will need to explain...why do you consider the straight 6 BMW turbo diesel as such ? Have you had a disaster with one ?
Click to expand...

Not personally but a friend of mine had an early bmw 180 straight 6, with a bmw outdrive, and had no end of trouble, Mainly with overheating, the marinising was rubbish one really bad thing was the turbo being lower than the intake, and getting flooded with sea water, the separate cylinder heads (sounds like a good idea) but if you disturb one you still have to renew the whole gasket set, and to top it all the engine was made by a firm called VM who have no connection with BMW in the slightest. Google it and see what the rest of the world reckons.

NO need to go that wide read this
http://www.ybw.com/forums/showthread.php?260509-BMW-Diesels-Avoid/page3
 
Last edited:
omega2 said:
Not personally but a friend of mine had an early bmw 180 straight 6, with a bmw outdrive, and had no end of trouble, Mainly with overheating, the marinising was rubbish one really bad thing was the turbo being lower than the intake, and getting flooded with sea water, the separate cylinder heads (sounds like a good idea) but if you disturb one you still have to renew the whole gasket set, and to top it all the engine was made by a firm called VM who have no connection with BMW in the slightest. Google it and see what the rest of the world reckons.

NO need to go that wide read this
http://www.ybw.com/forums/showthread.php?260509-BMW-Diesels-Avoid/page3
Click to expand...

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.
 
Omega
These are different engines. The engines I referred to are the BMW 2.5l to car engine, which have been marinised. They are bullit proof, by all accounts.
Read the post you copied and pasted for more details ?
 
You must log in or register to reply here.

Share this page

Top