Opinions on DD 8V71TI engines

[Bill Root]

I'm looking at a 53 MY with recently majored DD 8V71TI's. My current boat was repowered in 2003 with factory re-manufactured CAT 3126's. They are smooth, quiet, relatively efficient and use practically no oil between changes. I have no experience with the Detroits.

I'm looking to the expertise on this forum to help me understand the practical differences in daily operation and maintenance I can expect if I were to buy a boat with the DD engines. I've done a search of past threads, but they all seem to deal only with the technical specs of the engine. I get that. Results of a web search seem to get opinions that they are reliable engines but not very pleasant in a pleasure boat. I really want to know what they are like to live with, ie noise, fuel and oil consumption, ease of maintenance, daily operation. Most of our cruising is done at 7 - 10 knots. We do not run on plane very often.

I know there must be many on this forum who have practical experience with these engines, so I'm reaching out for your help. Thanks much.

[bigbill]

bill, they will burn, and leak oil. i was told that if you take a picture of a detriot engine, and hang the picture on the wall, that oil will run down the wall. bigbill

[fissioneng]

Bill,

Depending on the boat they are installed on, they can be very LOUD. Some folks like that. I have several 42C's and a 46C around me and it is hard to talk if any 2 start up at the same time. MY's seem to have more muffling than the C's.

[MikeP]

The good thing about DDs is that they are ancient technology so nothing is complicated and maint is quite straightforward; they are extremely reliable.

The bad thing about DDs is that they are ancient technology and so they are less efficient than modern engines. On a 53 MY at hull speed - around 9.5 Knots, they will deliver about 1NMPG - 9-10 GPH. At 18K, about as fast as you will get a 53 with 8V71TIs to go, 45 GPH would be in the ballpark. In a 53MY they are quite noisy, even at hull speed though that's relative, I guess, to what you are used to or what you expect.

DDs have a reputation for oil leaks but with a bit of work - which mostly consists of un-doing previous bad maint - they can be made to not really leak at all. They also don't necessarily burn much although that's also relative to what you may expect. When we used our boat regularly - which we no longer do - it would use maybe a gallon of oil in a season.

To say they are not very pleasant in a pleasure boat is probably true compared to the modern engines though it is not fair to compare the two. If you are buying a 30+ year old boat, you cannot expect to have the same conveniances and performance that a current boat would have.

It would be like comparing a 1959 Caddy to a 2010 whatever...the caddy was very luxurious, etc in 1959 but compared to anything made today it seems primitive and rough - though infinitely cooler! (No, I don't have one nor am I looking to buy one)

I m quite happy with DDs because of how easy they are to work on and maintain due to their simplicity. I would never replace the DDs with something else unless they were so badly damaged they could not be rebuilt because I don't think the cost benefit would ever support it. However, I have no experience with modern engines in, say a 53MY, so I cannot provide any sort of useful direct comparison.

A few years ago, a 53MY (I'm using that as an example because that's the only Hatt I know much about) would have sold for less if it had been repowered, even with "better" engines. When we were shopping, we found a couple like that and that was the comment from several brokers as well as being reflected in the price. I'd suspect that is not the case any more but at the time it was similar to putting small block Chevy in a 1964 E-type Jag. Yeah, it was a more modern engine but it reduced the price and the number of interested shoppers as far as resale was concerned.

SeaEric on this site would have a realistic view of that as far as a current view in the marketplace.

[TopHattandTails]

Bill,
The DD 871 is an institution unto itself. These motors are great. These are the same motors that the US put into tanks. On a Hatteras - they are great as well. Yes, the leak oil, burn a little, etc. I have found that my 871TI's, when filled properly - need about a half quart between the two of them every 50 hours or so. Not bad. THe trick is finding that "happy" level that each motor likes - no two are the same. So fill em up to the "fill line" and let them go down to the "low" line. Somewhere along the way they will stop loosing oil. Now mark that spot on your dipstick - and fill to that level. My mechanic tells me that due to installation differences (millimeters count) these motors have a sweet spot that will stop loosing oil at some point. Most people don't find it and keep overfilling - hence the mess. The 871TI's with Airseps are the best bet - no soot, and reduced oil leakage due to the vacuum seal action. Just keep a diaper under the motors and fill as above - no issues. These motors sound great, are dependable, and part of the Hatteras experience! I've been told that these motors take quite a lot of abuse and really need to be pretty screwed up (that's a technical term) to quit on you. Although never tested - I've heard you can throw a grenade in those ER's and still have a nice motor to get you home. Having had several motors in several boats over the years I like these old DD's over most of the other brands. Although you need to be o.k. with not having a sparkling white ER all the time... clean ER's - yes, no oil drips - no.

[chris piazza]

Everybody knows Detroits don't leak oil they SWEAT it!

[REBrueckner]

If you are looking at a boat that had a decent engine overhaul done, and especially if they have a few hundred hours to assure a good job was done, you don't need to worry about 8V71TI's.....they will surely outlast you. They ARE a bit noisy, do use more fuel than a modern electronic control four cycle diesel, but would be unaffected by a lightning strike, water sprayings in the engine room, and many have come home at half speed with something wrong that would have utterly stopped a higher HP high precision "modern" engine.

If I have my model numbers correct, CAT 3126's had their own set of problems...I posted about it after seeing a pair at DN Kelley Shipyard, Fairhaven Mass that had been removed because the owner had so myuch trouble with them....apparently CAT acknowledged the problem and gave him a good deal on new engines.....anyway the correct model number is in my post...

I owned a pair of 8V71TI's in a 1972 48 HATT YF and had major work done on them just after purchase...one had apparently overheated which a survey uncovered.....never had a problem in 11 years of 1500 RPM to occasionally 1950RPM cruise...about 125 to 150 annual hours...The only thing that stopped me once was a broken fuel line corroded by sitting in bilge water....
I cruised six summers full time between NY and Canada, the five just between NY and Nantucket, never did any engine work during the summers, and only routine zincs, lube oil and tranny oil, and two changes of coolant/antifreeze in the off season....once when I bought the bought and another about ten years later. I'd also spend maybe an hour per engine each winter wiping it down to remove any stains, oil drips, and making a close inspection of hoses, hose clamps, fuel connections and so forth....if I saw any rust/corrosion, I'd clean it with brake cleaner, coat with Rust Arrestor or an equivalent and repaint spray it with white paint. I never touched the Allison transmissions except to change oil and filters at about 500 hour intervals...

There is a real reason the 71 series engines (mostly naturals) were for many years the overwhelmingly most popular engines for lobstermen, scallopers, and draggers all along the east coast. Give them fuel, air and coolant and they very rarely fail.

I added RACOR CCV's myself (an easy job) (a complete post is here on Sam's) and loved them. I'd also recommend electric engine block heaters to warm them during cool weather starts...and water alarm flow meters to signal immediately when raw water is lost...

My only caveat would be if you are going to run maybe a thousand or two thousand annual hours, maybe a boat with recent brand new replacement engines would be a genuine consideration....

[Bill Root]

Thank you all for your responses. They have been very helpful. Just a couple more question:

We will use this boat to cruise up the ICW May to August. We'll find a place we like and stay for a month or so, then move on to the next spot. The rest of the year it will sit at a Florida marina going out for a day or weekend trip maybe once a month. How happy will these engines be at 8-10K speeds I run most of the time? I suppose I will need to run them at cruise occasionally, but I'm really not interested in running at 3.0 GPM fuel consumption rates any more often than I have to.

I want my engines to start and run properly. How many hours should I expect between overhauls based on the kind of use described above? What does an overhaul on these engines cost?


Thanks again.

[TopHattandTails]

Bill,
as in any motor- you got to run 'em. I run mine at cruise (1950rpm) all day long and then WOT at the end of a cruise. Faithfully. I don't run them under 1800 rpm unless I must (weather, marinas). I don't know how low you can run them, but you do need to get them within operating temps (175-180) for them to burn off moisture). That and regular maintenance is a perfect recipe for a long life. The 871ti's should not need to be majored untill 4,000+ hours. I'm told a good budget is $3k per cylinder. Other #'s I've heard are about $10-$15k per motor. I've got 1,560 (1980 MY) original hours and don't anticipate a major on my tenure (at 50-100 hours per year, that's another 25 -50 years). I do annual oil changes, bi-annual impellers, and perform an engine (and full boat) survey every 5 years for maintenace list generation. Expect to do belts and hoses or other deferred maintenance in first season to get you on track out of the shoot. Great motors. My protocol is probably not needed- but I believe that preventative maintenance is cheaper than needed maintenance. Plus it keeps me on the water, than tied to the dock.

[SKYCHENEY]

Bill,
9.5kts is the sweet spot for the 53. You'll be fine running there at around 1300rpms. Just run them up once per day for about 15 minutes. That's all.

[Glory]

Are 8V71s sweet? Let's see, if they baked desert that would be sweet, but they don't. If 8V71s chipped in for fuel, that would be sweet, but they don't. If 8V71s could wash the boat that would be sweet, I don't think that is happening either.

Now if i can go cruising for another year with out a pair of current engines in production that would be sweet, and I will , no doubt.

And those cruises will happen without the cost of a repower to the current tech, that is sweeet.

go figure

JM

[Bill Root]

Thanks again for all the great information.

[aeronautic1]

while I'm here, the interval between oil changes, would that be 250 hours?

[Canuck Dennis]

I have two boats, ea with detroits, one has twin 6's the other twin 12 's, I love em, talk to them often and they sure treat me right...at hull speed their fuel use is same as new high efficiency crap and they are easy to fix.
My 2c