8v92

[edward]

Horse power , 550 ,600, 720 ? What standard ?

 

[jim rosenthal]

I think all of the above, depending on who marinized them and what state of tune. Bearing in mind that the higher the wick is turned up, the shorter the life will be, all other things being equal.

 

[Seapig100]

I think all of the above, depending on who marinized them and what state of tune. Bearing in mind that the higher the wick is turned up, the shorter the life will be, all other things being equal.

I have read several places to avoid the 720. No experience just what I have read not even sure if that’s accurate.

 

[jim rosenthal]

It seems like the more power you pull out of an engine, the shorter the life expectancy will be, even assuming the maintenance is done and the engine is not ill-treated. I have read that fleet operators perform diesel maintenance based on the number of gallons of fuel that have gone through the engine. This makes sense to me, as the number of gallons of fuel burnt seems to equate roughly to the amount of work the engine's done. From what I've read and heard, 550hp for the 6v-92 and 720 for the 8v-92 is considered the upper limit of what you can get out of them.

Of course, you can always run them at lower loads, but I suppose the temptation is sometimes too much to bear...

 

[edward]

8v92 displaces 736 cubic inches. That is less than 1 hp per cubic inch. That is not unusual today ,but maybe too much in 1986? I guess they just increased the turbo pressure to up the hp. If the engine life is say 4000hrs before overhaul ,would the overhaul be reduced to say 3500 hours on the high hp motors? I am guessing that these 720hp 8v92s in the 56 motor yacht,would never be run too hard (maybe in a sport fish). Sure would be nice to have some gritty up when you need it. Edward

 

[jim rosenthal]

At the time, I think this was considered a high specific output. They did it by increasing the boost, fitting larger injectors, and altering the cam and injector timing. But since the engines aren't common-rail or electronically controlled, there is a limit on how much of all that you can do. 1hp/ci is about it.

As far as how long they last, you'd have to ask a DD mechanic. So much of it has to do with how they are treated- run regularly, not overpropped, maintained carefully, etc. Another way of saying it is that there are probably 8v92 naturals out there that are all used up at 2500 hrs, and turbo ones that are still strong at 4000- so much is in how they are cared for, like any piece of machinery.

For a long time, big DDs (the two cycle ones) were pretty much alone in the marine market. There wasn't a lot of competition for them, especially over about 450 or 500 hp. As boats got larger and needed to go faster, DDs just had the pressure and fuel turned up. Not a great long-term strategy, but it was what they had to work with. Later on, DD/MTU built some very good four-cycle diesels, some of which are still around. I think emissions did them in, but OBX charterers used to LOVE Series 60 DDs.

 

[edward]

Yep! Many charter boats out of Oregon inlet use to run a single 12v71. Edward

 

[Cricket]

Yep! Many charter boats out of Oregon inlet use to run a single 12v71. Edward

Running plank on frame or cold molded boats that are very very light, with no frills interiors, push super easy with their flat aft sections can't be compared to the weight and hard to push fiberglass Hatteras's. There's less and less single engine charter boats every year fishing daily out of OI, Hatteras, Morehead, etc, many of them are running the mechanical CAT 3412 @ 1000hp or less, there's a few CAT C18 ones too, really not many DD boats left.

 

[jim rosenthal]

Yes, they aren't exactly plush inside, unless you enjoy sleeping on plywood.... but they aren't yachts, they are day boats, and they do serve their purpose well. And, yes, they would be a lot lighter.

I remember hearing that a lot of those skippers loved Series 60 Detroits and were really sorry when they stopped making them.

 

[Seapig100]

The mechanics that service our fleet of trucks love the 60 series. All our trucks are now coming with 550 horsepower Cummins and they are beasts, I believe the torque is around 1800 pounds. A set of those would go nicely in my old 45c.

 

[jim rosenthal]

Which Cummins? some of those blocks are available in marine versions, I think.