More dumb Detroit questions

[keyzcaptain]

one more question if anyone can stand it, i just purchased a 43 DC with 6-71 TI's the sea trial was just done and i was told that the engines top rpm rating is 2100, I was under the impression they should max at 2450 under load any ideas on this?

 

[dfirst hatt]

My 871 naturals are at 2100 also,my engine surveyer said they are de-tuned.Different fuel rails ect.less hp.equalls potentially more total engine hours.rpms equates to 1 mph per every 100 rpm on my 45c.Good luck and congratulations on your new Hatt.

 

[Passages]

That does not sound right. My 6-71 TI's pumped to 410 were rated 2650 no load, 2500 loaded.
I believe they need to spin to design rpm regardless of tuning.

If they were detuned with smaller injectors, you'll need to adjust prop pitch to balance it out.

 

[saltshaker]

That does not sound right. My 6-71 TI's pumped to 410 were rated 2650 no load, 2500 loaded.
I believe they need to spin to design rpm regardless of tuning.

If they were detuned with smaller injectors, you'll need to adjust prop pitch to balance it out.

x2 2500rpms is what I've seen on most 671TI's. The naturals are 2300rpms and I think some of the early TI's may have been but 2100rpms seems too low for recreational use engines. Did they tell you the engines were rated at 2100rpm max or was that what they achieved at sea trial? Either way it sounds like you need to do some verifying to get the correct answer and most likely do some work to get the rpms where they should be.

 

[Xmeter]

My 1989 J&T 671 TI's are also rated at 2650 no load and 2500 loaded.
I'll never forget the first time the no load rpm was checked. These engine make a bit of noise compared to their gasoline counterpart that I was used to.

 

[Passages]

My 1989 J&T 671 TI's are also rated at 2650 no load and 2500 loaded.
I'll never forget the first time the no load rpm was checked. These engine make a bit of noise compared to their gasoline counterpart that I was used to.

LOL, same here. I remember my sea trial when the surveyor pushed it to no load WOT. I thought the engines would come flying out the ER.

 

[jim rosenthal]

That is called the "high idle". High as in noise level. Where the term "idle" comes in is anyone's guess. It never sounds like it to me.

 

[keyzcaptain]

wow thanks so much, it was my impression as well that they should have topped out higher, next step i'll contact the last know engine repair center, paint the bottom and re run the boat, hoping the bottom is the big issue here. thanks again to everyone very helpful.

 

[Bayside Bert54]

Eventually you will be able to zero in on the approximate horsepower (once you document which turbos and injectors are being used) and you might find an indication of who marinized the engine ... like J&T, Covington or Key Power. Adding to the confusion is the fact that the original injectors are no longer available and have long since been replaced with a different model number. Which new injectors approximately match up with the output of the ones used when the engine was new?? My 12V71TI engines use the 9215P injectors. They have 800 hp.

The surveyor should have been pretty unhappy with the 2100 WOT number.

Pay close attention to your oil, coolant, sea water cooling and engine zincs. You don't want oil in your coolant, coolant in the oil, fuel in the oil, sea water in the oil or sea water in the coolant All these are possibilities with the Detroits .. so take your time, take notes and pay attention to those engines.

 

[captddis]

That is called the "high idle". High as in noise level. Where the term "idle" comes in is anyone's guess. It never sounds like it to me.

"High Idle" is a Caterpillar term. DD uses ' No Load".

 

[Avenger]

Adjective

idle

1.(obsolete) Empty, vacant.
2.Not turned to appropriate use; not occupied.
3.Not engaged in any occupation or employment; unemployed; inactive; doing nothing.


It's not just Caterpillar, but I believe the concept is "not engaged in doing work" = no load.

 

[Boatsb]

Seems like a government to term to me. High and idle.

 

[keyzcaptain]

Well finally some good news, after cleaning and painting the bottom, low and behold, she came up to 2450 maybe not optimum but a darn sight better. Everything seems to have fallen into place, only thing left to mess with when i get there are the stabilizers, seems no one knows where the power swithc is and current owner hasn't had boat out for 3 years. just bought my case of 2040 filters for the trip to the Keys. Bought the wife her Hatteras shirts just to make sure the boat was rigged out properly. I'll do the alignment and repack the stuffing boxes, two new 8D's, garmin autopilot & chartplotter, and we're on our way to Cape May. Wonder how Paul is making out with his project in Rhode Island.

 

[GJH]

The "power switch" for the stabs is typically one of the ignition switches; look for a line coming off one of them with a fuse holder in it.

 

[saltshaker]

I have a separate switch with an indicator for mine. Always seen them mounted at the main helm. Make sure you call ahead and find out if the channels are marked and have been cleared before you go. There is a major project currently under way here in NJ to clear the waters from debris and dredge channels. Stay out of Barnegat Bay. There have been a lot of boats hitting debris in the bay. There's still a lot of debris washing up on the beaches so don't run too close to the beach. I would run her at least 5 miles off the beach from PT. Pleasant and not go in until Cape May. There wasn't that much of an impact at Cape May so they should be fine. Absecon should be fine if you wanted to stop in AC.

 

[omecojh]

I thing Detroit Diesel rated the engines at 390 brake HP at 2300 rpm but
JT got to 410 brake HP by rating them at 25/2600 rpm.

 

[captddis]

I thing Detroit Diesel rated the engines at 390 brake HP at 2300 rpm but
JT got to 410 brake HP by rating them at 25/2600 rpm.

No. the Covington 671 TI is 410 brake and 390 shaft @2500 RPM full load.

 

[GJH]

I have a separate switch with an indicator for mine.

Jack, you mean the "center-off-on" switch? Or do you have another switch that sends power to the system, and to which the fuse or breaker is attached?

On my boat and some others I know, the system gets turned on through the starboard ignition key and is fused there. The Naiad switch panel merely controls what the system does as noted.

Perhaps a "tell" is that a factory installed system has a separate power switch and breaker which would be easier to understand and more professional. Mine is obviously an after-market job as there is no mention of it in the "as builts" from Hatteras for my specific boat.

 

[Paul Gwiz]

I just bought a 1979 43dc W/ 671n , The survey said they are 238hp per ? I Am going to see it on monday.

 

[Paul Gwiz]

Got a clean biil of health on the dd's , They need impellers , I am just going to replace them both.

It may need cutlass beariongs ? Should I replace them both or Just the one ? I may have to move the boat to a different yard. I ask for the quote to replce them & they were fuzzy about the cost. He said " a couple of grand " to fuzzy on a number . I don't run my business that way. Has anyone had this done & is this a fair guess?

I run a custom Upholstery business in south florida , I do cars boats furniture & of course Boat Canvas. We have a small staff of 8- 12 guys, Right now i am re-doing a 53 sea ray salon , with leather, the guy just wanted leather for bragging rights, the stuff that is on it now is new . No benifit other that the smell of leather.

going to Rhode Island monday for w week to work on the boat , paint oil ect. I'm getting kinda excited to see this gem. What have I done ?