Looking for a pair of 671n

[bobdemauro]

I am looking for a pair of 671N to repower my 1979 58 Yachtfish. Will also look at Cummins 6BT's
Call Bob at 305 395-1089

 

[Dean B Luther]

i know were theres a pair of 853 ns great running motors still in a dry docked 41

 

[SeaEric]

Bob, I gave your # to a friend of mine Walt who has a pair. I asked him to call you.

 

[jim rosenthal]

I gather this is about to become a trawler? PM me if you want info on where to find Cummins 6BTAs, if you want.

 

[Boatsb]

No one wants the 8v71n boats because they are underpowered. I think you should look at future resale issues before making such a change.

 

[bobdemauro]

Bob, I gave your # to a friend of mine Walt who has a pair. I asked him to call you.

Thanks for the responce and help Eric
Bob

 

[SeaEric]

Old 871 N's are 350 HP each. The typical 671 N's are 310 HP. In a 58 YF, what are we're talking now a 12k cruise instead of a 13k cruise? It sure will make the enginerooms nice with skinnier engines!

 

[bobdemauro]

Thanks again Eric. I talked to Walt and sounds like he has a great deal for me. 671n's are 175 to 240 HP FYI. Yes 871n's are 350HP and what I have in the boat now are 871ti's 450 HP that are tired and fuel pigs! To go 16 knots with these engines they burn 28 gals. per. hour each The 671's at 10 knots burn 7.4 to 8 gals. per. hour each. Most people that have these Hatteras's 53' to 63' run them at 9 to 10 knots anyway. That is all I am looking for.

 

[SKYCHENEY]

Johnson & Towers converted 671n's that were 310hp. We had them in our 1975 43DC.

Also, I think your fuel burn numbers are off. On our 53, the total fuel burn at 16kts is about 40gph, not 56. And at 10kts, it is 12gph, not 16. Slow down to 9kts and it drops to 10gph.

I don't think you will gain any efficiency with the 671's.

 

[Boatsb]

Johnson & Towers converted 671n's that were 310hp. We had them in our 1975 43DC.

Also, I think your fuel burn numbers are off. On our 53, the total fuel burn at 16kts is about 40gph, not 56. And at 10kts, it is 12gph, not 16. Slow down to 9kts and it drops to 10gph.

I don't think you will gain any efficiency with the 671's.

Sky its not worth arguing when he already knows the answers. Especially when they are wrong. The refit with the longer engines and all the work will be paid off in 30 years at 200 hours a year at 9the kts.

I think its well thought out and a wonderful redesign like the 36 volt conversion.

 

[jim rosenthal]

Well, the advantage is that they won't cost much. And they are out of the boat so if they need majors they can be done easily. If they are only 30hp per side less it probably won't make much of a difference in performance- fresh 6-71s are probably as much power as tired 8-71s.

The length may be a problem, but I think the engine areas on that boat have some room in front of the engines, so more than likely they'll fit okay. And the weight is similar, so the boat won't need to be reballasted to correct her trim. The 6-71s are shorter in height than the 8-71s, and not as wide nearly, so engine access will be better- at least over top and on the sides.

But I still think that he'd be just as well served if not better by looking for more modern 4-stroke diesels. Cummins C series, which are easily found in 350hp rating, are much smaller than either of the GMs we're talking about, and would use far less fuel than either.

If this is a project he's doing himself, and the cost of the engines and gears is the big hurdle to jump, then maybe it makes sense.

Are 32v starters and alternators available for 6-71s? Might be worth finding out about. Maybe the ones from the old engines will fit. Most of the 6-71s I've ever seen were 12 volt.

 

[Boatsb]

Him I believe the 671 is as tall or taller than the 8v71. 2 cylinders or about 1/3 longer and quite a differently shape. By the time it's done I would think rebuilding the 8v71 rebuild makes sense. Then again as I said before it already decided without all the pertinent information being correct and confirmed.

Fwiw I think the 1510 hulls make lousy trawlers in comparison to real lrc and trawler hulls. Without stabilizers there is too much roll.

 

[bigbill]

my 58 yf with 450hp in line 6 cyl. john deeres cruises at about 17 knots at 27gph wot about 21 knots at 40gph and at 9 knots burns 8gph total. there is limited access in front of the engines, but plenty on the sides. the top is not a problem on the 58yf, there is plenty of height.
if i were doing this job, i would not go back with old school engines, i would use modern engines. it is the same amount of work to replace with old or new engines
if all you want to do is 9 knots, why not leave the tired 8v71's in there? they will probably out last you at 1000-1200rpm's

 

[bobdemauro]

Thanks for your response. I have been looking at John Deeres and Cummins. JD is very proud of there engines with the price they want. Cummins is a bit better, but I only an looking at the sleeved engines. Will keep looking for the right match.

 

[Boatsb]

Thanks for your response. I have been looking at John Deeres and Cummins. JD is very proud of there engines with the price they want. Cummins is a bit better, but I only an looking at the sleeved engines. Will keep looking for the right match.

Cummins 450c should work if the engine is not too long. They are sleeved and very affordable with the demand program. Look at the mounting angle as some installs require a down angle transmission. That engine is a long lived and efficient workhorse.

 

[Boatsb]

By the way I should also state that I am a cummins dealer at port Canaveral Florida. Even though I have detroits in my boat.

 

[jim rosenthal]

I agree. Especially at those power ratings they are widely available, and don't forget the "Recons" which to me look like new engines. And you would have room for a tool box in each engine room, not that you would be likely to need it.

There is a 53MY in our boat club that is repowered with 480Cs, and MUCH faster than stock. And more economical in the bargain.

 

[OBXTucker]

Are 32v starters and alternators available for 6-71s? Might be worth finding out about. Maybe the ones from the old engines will fit. Most of the 6-71s I've ever seen were 12 volt.

Yes. The LRC's came with 6-71N's. Standard on the 65' and optional on the 58's. Both were obviously 32V systems. Johnson and Towers still stocks parts (starters, Alternators, etc.) for them.

If/when it comes time to a repower on my LRC, I'll probably go with JD. Their reliability seems pretty amazing these days.

 

[jim rosenthal]

It IS amazing, although they cost like crazy. But they run and run and run. No accident that JD core engines are used in NL/Lugger products. You might look at Luggers, too, when you get there. Which is hopefully a long time off.

I would not doubt that the 6-71 is as tall as the 8-71, or close. All these old DDs are BIG engines. The 6-71 has the blower on the side, I think, but in-line sixes are taller since the cylinders stand up straight.

Cummins C series are also out there on the used market. I still think they would be a better choice if time and finances permit.

 

[dgltrader]

Hello there,

Had not seen the thread until now...

I am very interested if anyone can give a realistic cost for someone actually switching out to either of the Cummins options?
ReCons or otherwise, I assume the gears would also be part of the cost...and perhaps other running gear as well?

Are there CAT or other options forum members have taken? Can you fill in the costs for me?

I am aware the costs are high.
And the prospect daunting...at every level.

There are a lot of nice older 53-58's on the market, and yet many are at a point where it is hard to ignore this possibility or necessity if you are planning to buy one, live aboard and actually cruise it 5-10 years.

Reading the forum, it is clear that the costs of overhauling/rebuilding DDs is growing dramatically.
Some parts seem to harder to count on...either finding, or holding up (Reliabuilt injectors?).
And it seems gears can be even more of problem (in some brands).

Even getting the job done, being sure that it will hold up, and that someone will "stand behind" the work seems to be more problematic now.

So...if you love the boats, and are about to make it your traveling home for significant amount of time, it seems I need to consider all of the options when looking.

Also, I think that a 53 MY Lady Kristen sold recently in Annapolis (walczak yachts) that had been re-powered with... (from listing)
"Twin NEW "out of the box" 671's were installed in 2001 before embarking on the Great look trip.
Owner has operated this boat as a trawler and reports 10 gph at 10 mph (or 1 gallon per mile) and at 7.5 mph an amazing 4.4 gallons per hour (or .6 gallons per mile).
With this upgraded power is also reported she is able to cruise 20 mph at 2150 rpms.
Hours are 1751 on these engines."

...I wonder if anyone knows anything about how she performed overall?

anyway, please share any and all cost information to help in planning if you can.

also...was just at TrawlerFest Baltimore and managed to get a photo of "big" Skooch way over on the side of the harbor (hopefully it posts), really, really nice boat!