12V71TI service/experience

[nor'easter]

As my last few threads have stated, I am gathering info for a possible new to me Hatt in the future (after my current 39SX sells).
I am thinking of moving up to a larger C boat, and note that a number of them were fitted with 12V71s. The early 53C with Ns and later with TIs at 650hp. Given that engines displacement, I would think that the Ns or the 650 TIs would give acceptable service life if maintained properly. I have learned (mainly from here and bd.com) that the 735 and 800+ 12V71s are 1500-2000 hr plants, but have seen a number of Hatts with the Ns or 650 TIs in brokerage listings with 3000+ hrs and still "strong". Thoughts from the book of genesis or the grand poohbah?

 

[StratPlan61]

I have the small 'TI version' 12V71s (650hp). I like them and they run great. They have about 2400hrs on them and they smoke a little on start-up. I just added a set of Wolverine oil pre-heaters which eliminates 95% of any cold-start smoke. Admittedly I loaf them, partly to save fuel and partly to spare them any real stresses.
I have heard all of the stories: if you loaf them, you'll wreck them; you must run them at WOT at least 20 minutes everyday; etc. It's like asking somebody which viscosity oil to run in them - everybody has the 'right answer' according to them???
I think the SF had the bigger versions w700+ and 800+ HP ratings. People tell me these versions are tweaked up too high and don't last as long, who knows??
I baby mine and they work great. The engine surveyor said they could use rebuilds in the next few years - we'll see how they do. After running a 10-12hr continuous day, each motor takes 1-2 quarts of oil, not too bad considering the 13.5 gal oil capacity. Who knows, maybe I'll just feed 'em oil for awhile and keep talking to them? Good luck with your sale and potential purchase.

Bear'
1984 61 MY Strategic Plan

 

[luckydave215]

I have the 900 hp version and at 1900 hours the (very thorough) engine survey gave them a clean bill of health, expected another 4000 hours if treated the same as they have been. The previous owner (and I) usually run them at 1200 rpm, little more than displacement speed, with 20 minutes at 1800 every 5 hours or so.
If you run the piss out of them, expect expensive rebuilds at 2000 or less hours.
My friend is the captian of a long range charter boat that got over 100,000 ours out of a set by running them gently.
That's not a typo.

 

[Genesis]

The naturals, taken care of, will probably outlast YOU.

The turbo engines are another matter. As you approach 1hp/cid displacement, service life suffers badly if you actually use the power you have available.

This is true for all diesels.

As with any Detroit, the keys to long life are clean oil and never overheat them.

12s are lots of fun to run the rack on, but its not hard - just tedious.

 

[nor'easter]

Thanks.
I figured that the general rule of thumb regarding hp/cid applied here as well. I am also interested in knowing if these engines were notorious for anything in particular rearding their design or performance, as well as things to watch out for.
I couldn't see much on boatdiesel.com. There are pages and pages of 71 series posts, but mainly about the venerable 671 and then the 871.
Thanks again.
NE'r

 

[Boss Lady]

aren't the 12v71 are really just two 6v71s tied together or is that the 16v series that are?

 

[Freebird]

I recently purchased a 58TC with 12-71N's. They run fine and cruise the boat at 16-17mph @ 2100. I usually have time constraints when I cruise and would sure like to get into the 20's at cruise without abusing whatever puts me there. Can these engines be upgraded short of going with a major overhaul and adding turbo's? Would it make more sense to replace them with TI's to satisfy the need for speed? I had a guy tell me he would advise removing the 12-71's altogether when it came time to rebuild (referred to them as dinosaurs) and replace them with late model 6's or 8's. Anybody been there, done that?

 

[Genesis]

There's no inexpensive option here, and bolting turbos on those engines is a VERY bad idea - the compression ratio is different between turbo and NA engines, for one thing!

How much coin are you willing to toss on this? I'd go slow and save the fuel, to be honest - but if you must, then you're talking about a repower one way or the other.

 

[J's Dream]

aren't the 12v71 are really just two 6v71s tied together or is that the 16v series that are?

The 12's should be 2 6's together, the 16's are 2 8's.

 

[luckydave215]

My 12's are one piece blocks. I think they all are. (but I'm not sure)
It's the 12 and 1692's that are bolted together.
As far as maintainance or service issues, they are the same as any other 71 series DD's. Keep clean oil in them, DON'T overheat them, and flush out the heat exchangers every couple of years. Replace the raw water impellers and zincs annually.
BTW if assembled correctly, they hardly leak at all. Some examples none at all.

 

[Freebird]

There's no inexpensive option here, and bolting turbos on those engines is a VERY bad idea - the compression ratio is different between turbo and NA engines, for one thing!

How much coin are you willing to toss on this? I'd go slow and save the fuel, to be honest - but if you must, then you're talking about a repower one way or the other.

Yeah, I new the compression ratio would have to be lowered, but that could be done fairly inexpensively during a rebuild I would think. Oh well, I'll cross that bridge when I come to it. Just wondered if anyone had done it to know what I would be up against. Thanks for the reply.

 

[Boss Lady]

changing the compression ratio is the least of your problems, finding all the hardware to bolt on turbos and someone to do it is another issue. If you want to go faster than the installed power will let you, you should be prepared for sticker shock. Your boat will go as fast as you are willing to spend money to get it. If you have 650 HP now and 20 kts speed, and say you want 25 knots, be prepared to move up to 1000 HP and 40% jump in fuel burn to run there. You probably burn 40 gallons an hour at 20 knots, you will burn 70 gallons at 25 knots. $120 an hour versus $210. I would go slower, look for some good replacements at a good price, let them sit in the corner, and run the current engines until they go bang.

P.S. Dont forget about the cost of new larger exhaust, props and shafts.

 

[Genesis]

Yeah, in the year before I sold Gigabite we got used to a lot of 9-10kt running time.

To be honest, I liked it. Sure, there were times I still kicked it up to 18, but it was much more serene at 10..... and a hell of a lot cheaper!

 

[Freebird]

"run the current engines until they go bang"

This part of the plan is a given at this point. I'd like more speed, but my billfold needs a healing period having just bought the boat with a lot of work still left to do to get her into shape. I guess I just get jealous when I hear all you guys talking about your big engines. This kinda reminds me of my younger (dumber) days when I wouldn't have a boat that wouldn't run in the 80's or better. Once you got into the upper 90's, every additional 1 mph cost big bucks. "Speed costs money, how fast do you want to go?", remember that quote very well. It just doesn't seem fair that newer 6's and 8's are making as much or more hp as my 12 with half the weight, the other side of the coin. Sure would like to hear from somebody who repowered a 58TC just to compare.

 

[MikeP]

They may be making more HP for the weight but they are doing it at the cost of longevity. It's not hard at all to make a lot of power; what's hard is to make a lot of power for a long time. Light weight and high power are not the recipe for long life. Obviously, if you have sufficient wallet-weight, none of this really matters. As a former SS/A; SS/F (Mopars of course) drag racer and motorcycle road-racer, we spent tons of money to go that 1MPH faster so I understand your interest.

But I suspect that most of us with these "classic Hatts" are on this site because we DON'T have sufficient wallet weight to, as they say, play with the big boys.

As I've said many times, if I didn't do all the work on my boat, we could never afford to own our 53! Marina mechanic told me yesterday that the work I've done on our boat this year so far would have cost 30k had they done it. None of it was for major component breakdown. The total cost to me in parts was less than 5k. Labor ($120/hr)would have been the rest. I have to say that they seem to do a lot less work in an hour than I do!

 

[Freebird]

You're right about "wallet weight" being a factor for most of us with classic Hatts. I'm no exception here, but I have to say, I actually enjoy doing my own work, but I know my limitations. If my pockets were deeper, I'd still have a classic versus the new stuff. You can spot a classic Hatt from a mile away, but I have to be close enough to read the nameplate on the new ones to know they are Hatts. Too bad. What's up will all this new euro-crap with all the curves and funky glass patterns? The new Hatts are pretty I guess, but they are sort of like mid-size import autos, they all look the same.

 

[nor'easter]

As MikeP996 stated, I am here on this forum because I am not interested in a 30+ cruise speed being offered in many/most new convertibles. It just doesn't make sense to me to buy new/newer and know that you are going to burn that kind of fuel, or still go slow and not use the ponies you paid for.

Genesis, I saw your educated and insightful response to another boater looking for a newer 600K CV boat on another forum, and I can relate. I love the classics from Hatt in the 70s and 80s, and hope I can find one that my wife and I can offer a good home to. Many of them came with these plants from DD, and I am not hearing anything that would make me shy away from the 1271s at a reasonable rating (650hp or less in Ns).

 

[Traveler 45C]

The 12's are 6's bolted together, just like the 16's are 8's.

 

[doc g]

1271's are thier own block,1292's and 1692's are bolted together 692 and 892's......................Pat

 

[Traveler 45C]

Hmmm...

I must have read my 8V71 Service and Rebuild Manual wrong. For sure I will go back and look again...