Diesel outboard engine... could an actual inboard diesel be next?

[UNSTUCK]

Liability should be better with diesel as it's the safer fuel.

Turbo spooling has little to do with RPM and more to do with the blower vane pitch. You can make a turbo spool at pretty much any RPM.

[IDBoating]

I think the problem with diesel is that until you get the rpm up to the point the turbo kicks in you don't have much power. So not great for a tow boat!

Hmm... I'm not an engine expert, but I have two diesel engined vehicles and they have LOTS of grunt at low RPM's. One is turbo, the other not, but both can drag a lot of load up a hill in pure idle... my foot off the pedal, the ECU just increases the pulse width to the injectors. The RPM doesn't change but you can hear the engine working harder.

I'd think boating would be an ideal application for a diesel. Torquey environment, engine is constantly loaded (unlike a land vehicle where steady speed doesn't require nearly as much power as initial acceleration), and often a relatively constant RPM (think surfing or boarding, in cruise control).

[ChrisSnow]

Hmm... I'm not an engine expert, but I have two diesel engined vehicles and they have LOTS of grunt at low RPM's. One is turbo, the other not, but both can drag a lot of load up a hill in pure idle... my foot off the pedal, the ECU just increases the pulse width to the injectors. The RPM doesn't change but you can hear the engine working harder.

I'd think boating would be an ideal application for a diesel. Torquey environment, engine is constantly loaded (unlike a land vehicle where steady speed doesn't require nearly as much power as initial acceleration), and often a relatively constant RPM (think surfing or boarding, in cruise control).

what size diesels do you have? to give you an idea what's "normal" in the UK, a 2.0 turbo diesel would be 130-200hp, and a 3.0 heading for 300hp.

in my 2.0 175hp the turbo kicks in at around 1250 RPM, and then you start rapidly accelerating, before then you don't have much power, now obviously in a car this doesn't matter as you just down shift to accelerate and get into the power band of the turbo and shift up for fuel economy. now with a boat you only have a clutch so you need to get out of idle and get to the point the turbo kicks in, and that i think is the issue whereas a petrol (gas) has more power coming out of idle.

no doubt if you just have a massive diesel this probably doesn't matter!

[IDBoating]

I have a inline four cylinder 3.9L normally aspirated (loader/backhoe), and an inline six cylinder 5.9L turbocharged (one ton pickup truck). The latter does have a marinized version available and is often seen in seagoing vessels.

You're undoubtedly correct that a gasser has more punch off idle compared to a normally-chipped diesel (though some of the aftermarket chips do amazing things). I suspect that a marine version would have its curves modified to correct for that, for exactly the reasons you stated. But that would only be a very temporary lag... with ~600 ft-lbs of torque turning the prop, the engine would spin up VERY quickly and you'd soon be hearing from the turbocharger.

[Timmy!]

Mastercraft has tried a diesel option a few times:
VW diesel's
http://www.waterskimag.com/ski-boats...agen-tdi-225-6

http://www.boattest.com/review/maste...945_csx-265-ss

Yanmar
http://www.thesuperyachtreport.com/p...diesel-package

[Booms]

Did you guys not watch the video review of the 2016 Epic with a turbo diesel I posted yesterday?
No turbo lag, uses less fuel and is slightly slower than the gas equivalent.

[IDBoating]

I definitely watched it and liked what I saw!

[lee]

How about a Tigé 22i with a diesel engine?

[dom w. forte]

You still cant compare a diesel in a truck to a boat , trucks have multible ratio trans allowing for the acceleration , versus a fixed ratio trans, in a boat, here is where the problem comes in, you have to work with the prop, and it becomes a compromise, either it rips your arms off on the take off or you drag until the turbo spools up, they have gotten a lot better.

[IDBoating]

So you're saying it's a min-to-max RPM ratio thing? Gas engine with redline of ~6500 RPM is about 10:1 (~650 min, ~6500 max). Diesels are commonly ~3500 RPM max, so that would be a ratio of only 5:1 or 6:1. Presuming the prop was chosen for the proper max RPM's at WOT, that means when the transmission was engaged at idle its idle hull speed would be faster than with a gas engine.

Other vessels use diesels all the time. Do they have a smaller slow-to-fast speed range? Do they all have two-speed transmissions? If idle speed isn't the problem, what is?

[lee]

The Tigé in the above picture has a supercharged diesel engine in it.

[dom w. forte]

So you're saying it's a min-to-max RPM ratio thing? Gas engine with redline of ~6500 RPM is about 10:1 (~650 min, ~6500 max). Diesels are commonly ~3500 RPM max, so that would be a ratio of only 5:1 or 6:1. Presuming the prop was chosen for the proper max RPM's at WOT, that means when the transmission was engaged at idle its idle hull speed would be faster than with a gas engine.

Other vessels use diesels all the time. Do they have a smaller slow-to-fast speed range? Do they all have two-speed transmissions? If idle speed isn't the problem, what is?

My dads boat had twin detroit V653 diesels thet worked just fine , but bare in mind we were not concerned how fast we got on plane , thats where the issue with a wakeboard boat comes in , Im the dealer here in Fla, I was down at the lake back in 2003 through 2006 when MC and Yenmar were doind all the testing , they experimented with a 260hp and 300hp diesel, they prefered the 300hp , they tested with over 12 props, trying get a happy medium , but still couldnt get it perfect, also of interest I got to see the fuel consumption charts and they were burning on there best runs 8.5 gals, per hour , and at a 25,000.00 cost wouldnt have a good pay back in my opinion.

[IDBoating]

And yet we have that Epic diesel video.

[Stingreye]

Off topic but.... I didn't realize Epic was adding FAE to their boats from the factory.


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[Booms]

Off topic but.... I didn't realize Epic was adding FAE to their boats from the factory.

It could be because of the diesel fumes....