petrol to diesel conversion.

[Portofino]

I have often wondered why when repowering a small petrol why not use a car engine air cooled and just mitigate the cooling by fitting a bigger rad and enough "fan age " if that's the word .Size and position as suited
Thinking inner city buses etc or just a car stuck in atraffic jam !

Is all this "marine " stuff really necessary ,I mean REALLY !
A jack shaft to conect to outdrive .
Dry insulated exhaust ,or fit a belt driven water pump (like an alternator ) on the block to add seawater into a custom SSteel conection piece into the exsisting sterndrive exhaust exit hole ,

You could get a 150-180 hp VW /Audi 2.0 D from a totalled car for a peanuts compared to a Volvo penta D4 .

 

[Mr Googler]

There was a guy doing it with BMW straight 6's.

Looked quite a nice marinisation and from memory £2k a pop.

Having said that, I had a boat with 2 samurai gm v8 diesel conversion engines........that was not so great

 

[hg2016]

Not sure if diesel conversion is worth it, but given the low running costs of big modern outboards, they may be a better choice.

Pete

Thank you Pete,

 

[hg2016]

I may be many things but right up myself isn't one of them.

If it was a cost effective or easy job then many more people would be buying cheap petrol boats and converting them to diesel.

It isn't cost effective or easy. Hence my answer to your question.

Sorry, my comment wasn't directed at you or anybody in particular. just sometimes one can pick up a tone, even from a typed msg.
I thank everybody who has replied, without exception. There are clearly many very experienced and knowledgeable people out there.
Personally, I cant wait for the day when I have enough experience to help someone out.
Thanks to all.

 

[scottie]

How many people convert a petrol car to diesel?

 

[hg2016]

I have often wondered why when repowering a small petrol why not use a car engine air cooled and just mitigate the cooling by fitting a bigger rad and enough "fan age " if that's the word .Size and position as suited
Thinking inner city buses etc or just a car stuck in atraffic jam !

Is all this "marine " stuff really necessary ,I mean REALLY !
A jack shaft to conect to outdrive .
Dry insulated exhaust ,or fit a belt driven water pump (like an alternator ) on the block to add seawater into a custom SSteel conection piece into the exsisting sterndrive exhaust exit hole ,

You could get a 150-180 hp VW /Audi 2.0 D from a totalled car for a peanuts compared to a Volvo penta D4 .

This is something that has crossed my mind many times. I do think that the marine side of it is a little pricey.
The problem as far as I can see is that a car engine cooling system has air flowing into the rad. On a boat this would be more of a challenge. If you have a massive rad and fans then you have extra weight at the back of the boat. Also the engine on a boat is in a heavily insulated bay (especially on a diesel) and sound insulation will also equal heat insulation. It's almost encapsulated if you like. The key is to get fresh air into the engine compartment and onto those rads.
What a great project that would be though. (4l TD audi engine) yea haa!

 

[Mr Googler]

There's a classic saying.

"Experience is something you get after you needed it"

There are so many great people here that are worth listening to but at the end of the day, if you have the motivation, time and money, nothings off the table really. Someone has to do something the first time. The forum in my experience however will always guide you to the proven path for success. Thats the path i like but we are all different and i wish anyone well with something out of the box as it where.

"Ive put an audi engine in my boat" would be a great thread title

 

[Portofino]

This is something that has crossed my mind many times. I do think that the marine side of it is a little pricey.
The problem as far as I can see is that a car engine cooling system has air flowing into the rad. On a boat this would be more of a challenge. If you have a massive rad and fans then you have extra weight at the back of the boat. Also the engine on a boat is in a heavily insulated bay (especially on a diesel) and sound insulation will also equal heat insulation. It's almost encapsulated if you like. The key is to get fresh air into the engine compartment and onto those rads.
What a great project that would be though. (4l TD audi engine) yea haa!

What got me thinking about sans sea water cooling for the engine was certain Mase generators ,air cooled in a sound and as you infer "heat insulated " - box .This is allready in a hot ER .

What they do have is a water pump belt driven --think adding a water pump to the engine ?
That pump pumps cold sea water through a rad ( sized accordingly ) .
The cooler air is fanned though the fins on the air cooled engine ,and windings -- important stuff never gets wet .

So you could have a two rad compact set up .
Open duct or scoop on the side (s) or front ,under a seat -air first passes through the sea water cooled rad then fanned through the hot engine rad ,and a suitable gril at the back high up to let used air escape .
Or just a huge sucking type fan over a normal grill ,like a rear engined coach or bus .

But the Mase system is enclosed the box or your ER is cooled by the sea rad circulating round and round the cold rad .
Air vent for the engine can be remote -cos they will need a seperate air supply of course ,
What I,am saying here is the ER could be relatively enclosed ,cool and sound proofed

You don,t necessarily need large apertures

The seawater rad will need an anode ,but could be a Ford somthing or other -from "cheap parts direct " for £-100 every 5 years or what ever as opposed to £100 for a Volvo penta gasket ,or 6 inch,s piece of wiring loom ! every few weeks !!

And of couse as you said get a 4 L v8 D out of a totalled Porshe Panamera or Bentyga .
Which is actually a v quiet engine to start with .

 

[Seastoke]

a mate put a 4.2 turbo out of a land cruiser in a

 

[Mr Googler]

Yamaha Sti 420 was a Toyota base engine I think

 

[bluetooth]

Morning all,
has anyone done a petrol to diesel conversion on a 7.5/8m sports cruiser before. Is it a tough job if at all possible. looking for any advice about this.

I did it about 10 years ago on a Fairline Sprint. Cost about 4k for secondhand Yamaha engine/leg, 2k for transom alteration, 4k for engineer and materials etc. Whilst my conversion was the same as an article in MBM and was good to use for 5 years it was not worth it on reflection as all lost on resale although sale was v easy. The petrol engine was pretty shot when bought boat cheap though so plan made sense. My advice - don't; just buy a working diesel boat.

 

[tico]

Ok, I'll bite....yes, done it several years ago in a 26' Sunfury. Swapped 2x knackered petrols for 2x 140hp diesels.
in short it'll never make financial sense unless you get the boat and engines for nothing and you are a pretty able engineer with access to fabrication facilities.
However it resulted in a great package and took me about 3 months.
Not to be undertaken lightly.

Forget air cooling/automotive engine ..... the air requirements are enormous. Consider that a car engine rarely develops full power for more than a few seconds compared with marine engines running at 80%+ for long periods together with car cooling having great ram-air cooling (the fan only cools when stationary - hence engine idling at vv low power)

in short... forget it, as has been said before buy a diesel boat if thats what you want.

 

[oldgit]

A long time ago a Thames forumite with some considerable practical marine engineeering experience ( and plenty of time) fitted a marinised Mercedes diesel to a motor launch.
The main drawback despite some jiggery pokery with props and gearboxes was the thing was doing about 2000 rpm on tickover.
It created a very "busy" enviroment when boat was on the move.
Need to consider all sorts of stuff when altering any original drive components. ?

 

[snowbird30ds]

About 10 years ago I had an old RLM31 with smelly old bmc 2.5's sitting on rotten engine bearers so the engines had to come out and I didn't want to put them back in, never planning on being a fast boat I got a pair of 1.9l peugeot engines (one still in the car,one on a garage floor) rebuilt and marinised them re-using what I could and making what I couldn't, end cost of about £2.5k for two rebuilt and marinised engines on new glassed in iroko engine bearers, obviously no hours included in cost, enfield outdrives also rebuilt in that cost.
Didn't look too bad either and worked well.

 

[hg2016]

About 10 years ago I had an old RLM31 with smelly old bmc 2.5's sitting on rotten engine bearers so the engines had to come out and I didn't want to put them back in, never planning on being a fast boat I got a pair of 1.9l peugeot engines (one still in the car,one on a garage floor) rebuilt and marinised them re-using what I could and making what I couldn't, end cost of about £2.5k for two rebuilt and marinised engines on new glassed in iroko engine bearers, obviously no hours included in cost, enfield outdrives also rebuilt in that cost.
Didn't look too bad either and worked well.
View attachment 65027

Yes Snowbird, that's the sort of project I'm talking about. A bit of everything involved in that one. Engineering, Fabricating, laminating and lots of thinking. That's a really tidy and clean looking engine bay.
I work in engineering so I have access to lots of good stuff and machinery. I've worked for Fairline in the past and I've made loads of other patterns. moulds and components from grp and carbon fibre. Sometimes its not about the economic viability, its about the challenge and satisfaction. you can never count in your time, I know, but if you treat it as a hobby I think its great.
Hats of to you mate, nice job.

 

[hg2016]

A long time ago a Thames forumite with some considerable practical marine engineeering experience ( and plenty of time) fitted a marinised Mercedes diesel to a motor launch.
The main drawback despite some jiggery pokery with props and gearboxes was the thing was doing about 2000 rpm on tickover.
It created a very "busy" enviroment when boat was on the move.
Need to consider all sorts of stuff when altering any original drive components. ?

surely the 2000 rpm tick over would have just been a fuel metering issue would it not?

 

[Ferris]

You might like this thread then. A guy in the US developing a home brew marinising kit for the VW 1.9tdi engine.

http://forums.tdiclub.com/showthread.php?t=413125&page=10

He successfully mated it to a mercruiser gen1 outdrive too. Some nice engineering examples, such as casting a watercooled exhauset manifold along with remapping ecu's. Lots of work however and it seems that he has given up further developing the kit.

 

[robrennie]

Hi,

If you are going to do it, buy a complete engine and leg tougher that has already been re-furbished - or you will break your heart buying odd bits and pieces.

A KAD32 refurbished with a leg will set you back £15K or so - the job will be many times easier if you replace volvo with volvo of the same era, else you will get into some expensive engineering with the installation of the shield and engine mounts.

 

[hg2016]

Hi,

If you are going to do it, buy a complete engine and leg tougher that has already been re-furbished - or you will break your heart buying odd bits and pieces.

A KAD32 refurbished with a leg will set you back £15K or so - the job will be many times easier if you replace volvo with volvo of the same era, else you will get into some expensive engineering with the installation of the shield and engine mounts.

Thanks robrennie,
yes, I've had a look at the prices for recon engines and legs. All very eye watering. I think you would have to get the boat for nothing to make it viable, like many folks have said.

 

[piston]

I did it about 10 years ago on a Fairline Sprint. Cost about 4k for secondhand Yamaha engine/leg, 2k for transom alteration, 4k for engineer and materials etc. Whilst my conversion was the same as an article in MBM and was good to use for 5 years it was not worth it on reflection as all lost on resale although sale was v easy. The petrol engine was pretty shot when bought boat cheap though so plan made sense. My advice - don't; just buy a working diesel boat.

I don't recall charging you £2k for the transom work.....