Twins with Twins, Anyone?

kidturbo

kidturbo

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Jul 21, 2010
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malibu795 said:
Side track... what cause the crankshaft failure? Alignment pin shear, bearing spin or shear power? I've broken one each with the first two mentioned
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On Daves LMM boat I think it was like hitting 00 on the roulette wheel.

His stock LMM had 4 times the hours in same setup with no failure. Build a better bottom end, and it lasted under 8hrs. Only noted change was timing bumped up right before it snapped..
 
04LB7yz

04LB7yz

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Not sure if I am out of line here but that sounds like a lot of money to put into a less than ideal hull. Baja's are built well and handle big water very well but speed and performance are definitely not their strong points... :confused: but then again I am not the one flipping the bill :thumb: None the less it will definitely be unique and one of a kind! And maybe it will spark some interest in some other people of the offshore community to build some nasty diesels! :woott:

Having a Baja that does 100+ in its self is pretty impressive! :thumb:

Those Weismann drives are pretty impressive, but my knowledge on them is not very good. What kind of benefit do they offer over a #6? The only failures that I have heard of with the #6 was when mercury was testing the 1650's and were twisting splines when turned up closer 2000HP I believe that's why they came out with the M8.
 
SmokeShow

SmokeShow

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Sorta unrelated because its based on a cummins, but I thought this was an interesting thread over on CompD. IDK if there's any nuggets of info. in there for you or not but there might be. As far as I know, it never got completed. At least its never been updated over there that it has been.

Cummins Poker Run Boat
 
CaptPhil

CaptPhil

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Are those wet sump sixes? getting rid of those will give a nice bump in net power.

I've seen other Bajas with sixes, but they may not have been factory.

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2004LB7

2004LB7

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SmokeShow said:
What's considered a comfortable "load" to be on an engine for an extended time? No engine is made for 100% load 100% of the time, that would be grossly over built or overworked wouldn't it?
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that is not quite true. many engines are designed and run at 100% the whole time. Generators, ship engines, Locomotives, etc. the differences are that 100% for them is like 30-50% for an automotive application.

example, some of the generators i work with are 4.5 liter at 90 HP. that is 20 hp per liter. the Duramax at 397 hp is 60 hp per liter. maybe that is what you meant by grossly overbuilt?
 
kidturbo

kidturbo

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Typically throttle position and load are linked together on a boat. The prop pitch plays largest roll in this value. With my LLY boat if you were at 50% throttle it was typically 45-60% load according to the ECM's calculation. What would vary that number is prop pitch. Bigger pitch = higher load, smaller pitch = lower load values and lower speeds.

On a gas motor you typically try to find a prop that allows the engine to run at peak cam torque curve. Go to big on pitch and you run out of power before reaching full RPM potential of the engine.

With a diesel your obviously not gonna run at 1400R's and have any top speed. So you might only be 30% load at peak torque curve, but then 90% load at 3800R's. So you need to have everything setup to run those high R's all day long loaded, but typically your outside peak torque of the engine.
 
Dozerboy

Dozerboy

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Can't you get the prop over driven enough to compensate foe the low rpms? Even something custom build sounds cheaper/ better then getting the motor to live at that load.
Why are EGTS an issue at those RPMs?

I'm learning here too. I hate the water/boats, but this sounds cool

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04LB7yz

04LB7yz

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When I joined this forum and put that on here i lived in Bagley MN which is south east of you probably a half hour or so... Now I live about an hour north of the cities
 
kidturbo

kidturbo

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Dozerboy said:
Can't you get the prop over driven enough to compensate foe the low rpms? Even something custom build sounds cheaper/ better then getting the motor to live at that load.
Why are EGTS an issue at those RPMs?

I'm learning here too. I hate the water/boats, but this sounds cool

Sent from my SAMSUNG-SM-G900A using Tapatalk
Click to expand...

The drives I've switched to use straight cut gears that you can set to about any ratio you imagine. BUT, imagine your truck having no transmission and only what gears you setup the rear end with. Now hook to a trailer... lol

Hence the 2 spd trans options.
 
SmokeShow

SmokeShow

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It still seems to me that "gearing" via props & transmissions and a build that can make the power you need without being at full load is the only shot. I'd be blown away if there's any duramax on the planet that can live at or near full power over 1000 prop hp for even 10min straight let alone hours at a time. If that's the requirement, I can't wait to see what the build consists of & how long it lasts!!
 
NC-smokinlmm

NC-smokinlmm

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May 29, 2011
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The big blocks can do it so I don't doubt a duramax can as well. I work with 1200 to 1500 hp diesels everyday that run at 80% load for 2+ hours straight. Granted they are huge but so are the boats they push...
 
THEFERMANATOR

THEFERMANATOR

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Wonder if one could find a set of the turbo 400's, and adapt into it. Set them up with no converters to do away with lockup concerns. Everybody says the 4L80E's weak point is OD, the 400 is basically teh same without OD, and theres plenty of drag trucks running them with big HP. It might would allow for dropping into 3rd say for cruise, but use 2nd for acceleration. I know they make the 2 speeds as well, jsut throwing out an idea that may be more advantagous in the long run tuning scheme. The limited RPM range coupled with the added cylinder pressure will be the killer here. Most don't realize just how hard it is to push a boat for hours on end, and have an engine live. Imagine dragging 80K lbs up a 6% grade for HOURS non stop.
 
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