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aneal000

Drop in Diesel Replacement for the 8.1

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aneal000

Found this interesting.

Marine Diesel

The more time I spend on their site the more I find. It looks like they also do small block replacements and have already done a Response LXi...

Boat Model: Malibu Response LXi

Weight as Tested: 2700 Lbs

Drive System: ZF 1.20:1 Gear Ratio

Propellers: 14 x 23P

Cruise Speed: 43.6 Mph at 3000 Rpm

Top Seed: 52.3 Mph at 3600 Rpm

Diesel in a Response LXi

Edited by aneal000

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aneal000

"The MarineDiesel product line is the only True Ski Boat/Tow Sport Marine Diesel Engine offering superior acceleration and packaging characteristics than that of competitive small displacement , inline marine engines. Serious ski boaters demand serious low end acceleration and top speed performance that only MarineDiesel offers."

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aneal000

I made a phone call - their 330HP "Hammerhead" (interesting name huh) Inboard motor sells for $21,300.

Edited by aneal000

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aneal000

Group buy anyone? :)

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RTS

I was just skimming through the above site, and came across something that's worth considering...

I'm far from an engine expert, but my understanding is that diesel engines produce great torque and turn much lower RPM's during normal operation. We have a diesel at work that redlines around 3K RPM, if I'm not mistaken.

So this leads me to assume that the prop piches and sizes will change dramatically when you go from a gas to a diesel, it would be greatly increased (the pitch)

How will this affect the idle speed of a towboat. I for one would not want to be idling around at 7-8 MPH. Not only would it make it more dangerous to pick up a downed skier and make docking more difficult, but at those speeds the boat would be producing wake that would most likely be unacceptable in a no-wake-zone.

Other than feathering the transmission in and out of gear (not the best solution in my opinion) how will this problem be handled?

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RTS
I made a phone call - their 330HP "Hammerhead" (interesting name huh) Inboard motor sells for $21,300.

At roughly 3-4 times the cost of a gasoline powered 350, I don't see why this diesel is being seen as a practical replacement for what's currently available.

Are they just laying the groundwork for if/when these engines become less pricey?

Even at the 30-50% savings in fuel costs, it would take a very long time to break even on something like this.

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aneal000
How will this affect the idle speed of a towboat. I for one would not want to be idling around at 7-8 MPH. Not only would it make it more dangerous to pick up a downed skier and make docking more difficult, but at those speeds the boat would be producing wake that would most likely be unacceptable in a no-wake-zone.

Other than feathering the transmission in and out of gear (not the best solution in my opinion) how will this problem be handled?

Yeah you're right about the idle speed/prop pitch. The website says that they typically increase prop pitch 1 for evey 200rpm's of lost engine speed. Whcih they also say typically means most use a prop that's about 5 pitches higher than what it started with.

Unless idle speed of the motor was extremely slow the actual idle speed of the boat would be pretty quick. I've seen some big boat tests that use diesels and they "idle" at 8 knots (~10mph) at 800rpm. Way too fast for a ski/wakeboard boat. Would be interesting to see what idle speed is on oh, say the RLXi they tested.

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WakeGirl

I suspect that the only way it would work would be to put in a multi-speed tranny, ala MB Sports.

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mrothwell

You can generally idle a diesel slower than a gas, so they might just screw down the idle. Would be a fun experiment.

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BlastRlxi

From the picture, it looks like they had to seriously increase the size of the engine cover. It sticks way up to cover the diesel.

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SacRiverRat

what is the 'upside'? Dontknow.gif

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bevans

Finding diesel stations for the truck is hard enough let alone trying to find that stuff on the water!!! No thnx!

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GoldschlagerVT
From the picture, it looks like they had to seriously increase the size of the engine cover. It sticks way up to cover the diesel.

Looking at the 3rd picture down, it looks like they took the factory cover, but made a base for it that is 6-8 inches tall. IMO, in the sunsetter it wouldn't look bad. In the response, with how low it sits, it'll probably look funny.

Looking at this picture, how are you supposed to see your skiier when the engine is almost as tall as the window. Guess you have to get a mirror that sticks up.

post-1521-1149780282_thumb.jpg

Edited by GoldschlagerVT

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gonorth

The idle thing would be the big hitch, my pickup has a cummins diesel and and you don't need to put your foot on the petal much in town, it idles at about 25MPH, and that's in low gear. You can coast a long way decellerating from 65 to 30 with your foot off the 'gas'.

At first I was gonna say the fuel savings would be offset some because diesel fuel has been running 10-20 cents a gallon more than 89 octane gas. But then it occured to me that you could get by on off-road diesel fuel in a boat and that varies by state, in general probably 40+ cents a gallon cheaper than gas. Even still, you would have to run a LOT of hours per year to make up the cost difference in fuel savings. Add to that the fact that some people just don't appreciate diesel exhaust smell, or spilled fuel on their boat, and black soot all over your swim platform. Also, hard enough to find a good gas engine mechanic, diesels don't require much maintanence but when they do they need specialized skills. You would really have to appreciate the 'tone' of a diesel to want one in a performance boat.

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