i tried to attach a photo of the Jolly Drive but it looks like I am not allowed to do so under new rules so if anybody's interested, PM me.

Rik, I believe those GM blocks are marinized in Sweden. I had those in a client's Sunseeker and the problem was that they simply were not any good. We had a twin-turbo 400+ hp version and it was a nightmare. Pity though because as far as repowering a gas V8 boat with diesels goes, it didn't get any easier than that. Take the gas motors out, drop the diesels in on same engine mounts, end of story! As for the inline ASD8s, the problem is very practical in that case. It is really suited to boats 40' and + in length which means that you would have to go for triples instead of twin to get any respectable speed which would not leave a previous owner of 500s very frustrated. And then, you have an extra engine, an extra drive... and even if the drive is only 12K, the comparison gets more difficult.

What is the size and weight of a 440 Yanmar compared to a BBC?

The Yanmar 440 has a weight of 1,136 lbs minus gear and water! Rigged with marine gear and with its fresh water coolers full of water the engines have a weight of about 1,500 lbs ea.

The weight of a BBC? Depends upon setup, blown or non blown? But most likely even the biggest powered BBC will be lighter than the Yanmars. This does not make them best engine for the cats.

As for needing triples, that's not accurate. The 42' Fountain Lightning uses twin engines as well as the Hustler 388. The 38 Power Play also used twin Yanmar 440’s and the Outer limits 37’ used twin 420 CAT’s. etc. etc.. The large cruisers use triples with the Yanmar 440 engines due to the low power of the engines. (48’ Fountains)

Now the Buzzi drives have four engines to make the Hustler 50 run. Practical? It’s all about the application not about a conversion from gas to diesel.

No one is really going to be converting a fast gas pleasure boat to diesel engines. OEM will be where the sales are and the need for two, three or even four engines will depend upon application, not drive make.

The Konrad 540 I would think would fall in between the Bravo and the #6.
I wish Ford would move more into the marine market with their PSD.

Rik, the problem with Yanmars is the fact that they are longer than a BB due to their inline-6 configuration. They also need a trannie which makes the whole assembly too long for standard engine room space. For example, a Hustler 388 with Yanmars has to have a specially-made longer engine space and consequently a smaller cockpit. So it's not really a stock Slingshot. To put in Yanmars without manipulations of that sort, you need to go to the 40' Sport in Hustler's range which will do 68 mph with that setup. And my point is that this is too slow for people used to 85 or more mph provided by 500s or 525s. I am not so familiar with other boats you mentioned but I believe they all had a bit of trouble to fit Yanmars+trannies+drives in standard engine compartments. And for manufacturers to readily offer diesel options, this switch to diesels must not involve redesign efforts of that sort. Thus, what is needed is something like the new ASD6 where the trannie is in the extension box outside the hull which takes takes the trannie out of the engine compartment and makes a Yanmar fit without problems. Trouble is, an ASD6 cannot take the 440's torque. Therefore for people to really take up diesels, they need to be 1) easily adaptable into standard engine compartments and 2) offer performance close to that of stock gas motors. And we're unforunately not there just yet. Hustler has the performance but not the ease of rigging, Fountain 42 did 82 mph but that was not really a production boat plus they also played around with the engine space, the Outerlimits with twin Cats probably does not come close to 80... I was not necessarily talking about conversions, I was talking about comparisons... which people inevitably make when shopping for a boat.

WAS a gap. Now there is this package, available right now, today. It is currently offered only in the 310 hp (298 prop) version, but there will be a 350 hp (336 prop) version next fall, and possibly a 400 shortly after that. The 400 will have a peak torque of 718 ft-lbs, and the drive is rated for commercial use. The entire package is brand-spanking new from the crank pulley to the prop nut, full electronic control, common rail electronic injection, four valves per cylinder, servo shifting, direct hydraulic steering, and emmisions-legal for 2006 already. It's only 5" longer than an 8.1 Gas V-8 (46" vs 41"), and weighs about 375 pounds more. 310 hp @ 3500, 555 ft-lbs @ 2500.

Volvo-Penta D6-310 with "up to 50 mph " drive (DP-H):

With "over 50 mph" drive (DP-R):
Full specs are here. Both of these drives are shiftable, so there is no transmission required, as is the case with Arenson/TriMax/Konrad/Merc #6/BPM, etc.

Better shot of the drive:

So the verdict for a 30' single is?

It looks like you can fit it in your engine compartment -the added length requirements that is- your choices are:

1) Buy a Merc-Yanmar 315HP package.
2) Buy a Yanmar 440HP and find your own drive. Call Arneson, IMCO, Teague, buy a #6 -it's your choice.

The constant knock I am hearing is that with a single, the steering with an ASD at slow speeds and docking is a nightmare. You simply don't have the range of thrust (side to side) that an normal outdrive can provide, but the trade-off is the added performance and efficiency and rooster tail.