New Cummins/Mercruiser Project
11-04-2008 | 09:26 AM
#163
SeaRay Sundancer
Joined: Nov 2005
Posts: 2,914
Likes: 0
From: SW Missouri
How does she sound? Bad Azz! 
http://www.youtube.com/watch?v=FqVMk...eature=related
Like a couple of heavily juiced dodge cummins.
http://www.youtube.com/watch?v=FqVMk...eature=related
Like a couple of heavily juiced dodge cummins.
11-04-2008 | 05:54 PM
#165
Registered
Joined: May 2006
Posts: 33
Likes: 0
From: Highland, CA
Demo rides were being offered and I was lucky enough to get a spot on one in Ft Lauderdale. It was enlightening to say the least, and overall, I thought it was a nice package. The installation looked very nice.
The drives are at 1.35 now, I think they're going to try a 1.25 this week with a stop by X site on the way back to CA. It should help a bit with allowing a reduced prop pitch. It didn't exactly jump up on plane though. Idle speed (boat, not engine) was higher than I'd expect though backing the boat into a tight spot posed no problem on this particular day. I don't think "no wake" would be possible without taking it in an out of gear. Like Joe said, too much pitch.
The ride was 95% 5-10 mph out of the marina/harbor area so I don't have much to go on, but it seemed that it needed CMD participation on the engine calibration side of things. He revved it up in neutral and no load speed was 3450 rpm, but it seemed to take for ever to get there. Might be some cal changes to let it ramp up quicker. I don't know if these had production calibration or something special for the application. It seemed to me that the engines had more in them. Maybe CMD is trying to protect the NXT drives with a nice soft torque curve?
480hp is only 740 ft-lbs at rated speed. Torque limiting to 750 or so would take a lot out of the mid-range power availability.
The drives are at 1.35 now, I think they're going to try a 1.25 this week with a stop by X site on the way back to CA. It should help a bit with allowing a reduced prop pitch. It didn't exactly jump up on plane though. Idle speed (boat, not engine) was higher than I'd expect though backing the boat into a tight spot posed no problem on this particular day. I don't think "no wake" would be possible without taking it in an out of gear. Like Joe said, too much pitch.
The ride was 95% 5-10 mph out of the marina/harbor area so I don't have much to go on, but it seemed that it needed CMD participation on the engine calibration side of things. He revved it up in neutral and no load speed was 3450 rpm, but it seemed to take for ever to get there. Might be some cal changes to let it ramp up quicker. I don't know if these had production calibration or something special for the application. It seemed to me that the engines had more in them. Maybe CMD is trying to protect the NXT drives with a nice soft torque curve?
480hp is only 740 ft-lbs at rated speed. Torque limiting to 750 or so would take a lot out of the mid-range power availability.
11-04-2008 | 06:35 PM
#166
Registered
Joined: Jun 2004
Posts: 1,395
Likes: 16
From: Freehold, NJ
mthill,
My thought is 1:15 or something close to that. Those gears may not be avail, but that's the range you need.
The faster the prop rpm the smaller the dia of the prop and that helps idle speeds tremdenously because you have lots of slip with the little dia prop and a big heavy boat. Big prop, big bite can't idle slow.
Was CMD able to tell you how much power they were putting out with those props on?
That was always my first test on a boat (pre electronic days), record the boost at each 100 or 200 rpm and go back and put a similar engine on the dyno and load it to that boost at those rpm's. I could see right away how much Hp we had left.
That was always a problem with diesels, you run up against the governor and you don't now where you at. Props are expensive and time consumimg, you know how much HP is left and you know where to go from there with less guess work.
I'm sure with all the electronics they know exactly where that engine is at?
Joe Gere
My thought is 1:15 or something close to that. Those gears may not be avail, but that's the range you need.
The faster the prop rpm the smaller the dia of the prop and that helps idle speeds tremdenously because you have lots of slip with the little dia prop and a big heavy boat. Big prop, big bite can't idle slow.
Was CMD able to tell you how much power they were putting out with those props on?
That was always my first test on a boat (pre electronic days), record the boost at each 100 or 200 rpm and go back and put a similar engine on the dyno and load it to that boost at those rpm's. I could see right away how much Hp we had left.
That was always a problem with diesels, you run up against the governor and you don't now where you at. Props are expensive and time consumimg, you know how much HP is left and you know where to go from there with less guess work.
I'm sure with all the electronics they know exactly where that engine is at?
Joe Gere
11-04-2008 | 07:46 PM
#168
Registered
Joined: Jun 2004
Posts: 1,395
Likes: 16
From: Freehold, NJ
obrien,
I have to debate your remark about larger dia.
People have 43 Nortechs, 42 Cigs with Bravo drives on them, what dia props do they run?
Why when someone says diesel do people automatically jump to "larger dia"?
Diesel race boat after diesel raceboat run small dia props - my personal experiences aside how can they all be wrong?
I'm not disputing you, I want to know what experiences do you that have that make you say what you said?
Joe Gere
I have to debate your remark about larger dia.
People have 43 Nortechs, 42 Cigs with Bravo drives on them, what dia props do they run?
Why when someone says diesel do people automatically jump to "larger dia"?
Diesel race boat after diesel raceboat run small dia props - my personal experiences aside how can they all be wrong?
I'm not disputing you, I want to know what experiences do you that have that make you say what you said?
Joe Gere
11-04-2008 | 10:46 PM
#169
Registered
Joined: Mar 2008
Posts: 529
Likes: 14
Most of the stuff we have played with have been in the 18-21 range.
Most recently we have been doing a few 50' boats with twin 480s running 21x32 Acme props for speeds in the 64-67 mph range. Granted we have been running ASD8's so we are not limited in diameter.
the 39 nortech that the boss has is running 18X32's I believe and that boat runs in the 80-83 range consistently.
The only Nortechs running the bravos and diesels are the 43's with triple 6lp 315s. those are limited on diameter as well.
All I am getting at is the majority of stuff we run, perform better when you can take advantage of the larger diameter.
Most recently we have been doing a few 50' boats with twin 480s running 21x32 Acme props for speeds in the 64-67 mph range. Granted we have been running ASD8's so we are not limited in diameter.
the 39 nortech that the boss has is running 18X32's I believe and that boat runs in the 80-83 range consistently.
The only Nortechs running the bravos and diesels are the 43's with triple 6lp 315s. those are limited on diameter as well.
All I am getting at is the majority of stuff we run, perform better when you can take advantage of the larger diameter.
