1968 50' Hatteras Motor Yacht FOR SALE $79,900

[Finalee]

Not sure I agree with that as in 1989 I owned a 1978 40C Egg Harbor with 6n71 naturals where previous owner managed to harm both to the extent they needed complete rebuild at around 5,000 hours.

He was pretty meticulous type too so can't imagine him not changing the oil.....but I can imagine him running the boat flat out most of the time as he kept it in Rudy Inlet (Virginia Beach) and was thus close to the offshore fishing action.

Different motors and type of use. Terrible comparison! Felicity appears to be a Super deal for someone, and those motors have a fantastic track record.

[Milacron]

Different motors and type of use. Terrible comparison! Felicity appears to be a Super deal for someone, and those motors have a fantastic track record.

6N71 is same engine with 2 less cylinders. As to type of use you made what sounded like a blanket statement about the motors regardless of type or use. Plus we are both guessing about the use....for all we know this one was WOT most of the time and the Egg was not ! But we are probably guessing correctly.

[oscarvan]

6N71 is same engine with 2 less cylinders.

Correct me if I'm wrong, but I believe the 6N71 is a straight six, whereas the 8V71 is a V-8.....

https://en.wikipedia.org/wiki/Detroit_Diesel_Series_71

[Milacron]

Correct me if I'm wrong, but I believe the 6N71 is a straight six, whereas the 8V71 is a V-8.....

https://en.wikipedia.org/wiki/Detroit_Diesel_Series_71

No, you're right.... plus I mean 6-71, not 6N71. Still, I heard from many mechanics the 6-71 was best engine Detroit ever made...so the comparison is still valid...if anything the 6-71 should last longer...and yet they don't always...

[SKYCHENEY]

We owned many of them in industrial applications that got that kind of life. One example otherwise is less than convincing.

[Walter P]

I think that applications such as Sky's are much more friendly to the long life of a DD 6-71 than on a boat, especially one that is not used a lot and when it is, it's run hard and put away wet. My first Hatteras was a 43DC with JT6-71's rated at 310 HP ea. By the time it had about 4500 hrs they smoked quite a bit so they were rebuilt...great job, ran like new again. I usually ran that boat at about 2200 - 2250 rpms which is probably a bit too hard.

About 25 years ago we became friends with a couple with a 1968 50MY. It had 8-71 Naturals (I think they were 325 HP ea) and that boat was usually run on the pins and still got well over 5000 hrs on it.

My conclusion is that there is no hard fast rule as to how many hours a 71 series Detroit can get before it needs to be rebuilt. The 6-71TIB's @485 don't seem to get many hours between major overhauls. Detroit diesels were/are great engines and would probably still be used if they were able to meet emissions standards. The only sure way to be sure of their condition is to have a very competent DD mechanic do a complete survey, including compression test etc...

Walt

[Milacron]

I think that applications such as Sky's are much more friendly to the long life of a DD 6-71 than on a boat, especially one that is not used a lot and when it is, it's run hard and put away wet.

Exactly...industrial applications a whole 'nuther ballgame. Boats are possibly the harshest conditions for an engine there is. It would be interesting to know what is the highest hour non rebuilt Detroit engine on a boat that still specs out ok as far as oil pressure, WOT and low smoke goes in each Detroit model on a personal yacht. Not a piling driver barge used nearly every day, but a personal yacht used sporadically like they usually are.

The highest hour diesels I have noticed in Yachtword ads are typically trawler style yachts using relatively small Alaskan or Ford Lehman diesels. But I haven't been following Yachtworld ads all that long ...some marine mechanics here will probably have a better feel for this.

[Finalee]

Exactly...industrial applications a whole 'nuther ballgame. Boats are possibly the harshest conditions for an engine there is. It would be interesting to know what is the highest hour non rebuilt Detroit engine on a boat that still specs out ok as far as oil pressure, WOT and low smoke goes in each Detroit model on a personal yacht. Not a piling driver barge used nearly every day, but a personal yacht used sporadically like they usually are.

The highest hour diesels I have noticed in Yachtword ads are typically trawler style yachts using relatively small Alaskan or Ford Lehman diesels. But I haven't been following Yachtworld ads all that long ...some marine mechanics here will probably have a better feel for this.

This is another "For sale" thread that has gone sideways .
The boat sure looks great. I have not seen anything better in that price range.

[Walter P]

Fred, With all due respect, you are wrong. The thread is about a members boat for sale and an important component is the engine hours. We have been posting regarding the pros and cons of the engines, including examples from various applications.

Walt

[SKYCHENEY]

Exactly...industrial applications a whole 'nuther ballgame. Boats are possibly the harshest conditions for an engine there is. It would be interesting to know what is the highest hour non rebuilt Detroit engine on a boat that still specs out ok as far as oil pressure, WOT and low smoke goes in each Detroit model on a personal yacht. Not a piling driver barge used nearly every day, but a personal yacht used sporadically like they usually are.

The highest hour diesels I have noticed in Yachtword ads are typically trawler style yachts using relatively small Alaskan or Ford Lehman diesels. But I haven't been following Yachtworld ads all that long ...some marine mechanics here will probably have a better feel for this.

Boats are a great application. They get to warm up before hard use and they get to cool down before shut down. The air is clean which is not the case in most land based applications. The only issue for a naturally aspirated marine version is salt. In freshwater, they can sit without much issue. In salt air, they will corrode the liners that are exposed to air if they sit for long periods. But don't compare naturals to any other version. They will a last a very long time.