let's talk engines

[Woodsong]

THis may be opening a can of worms, but one of the boats I am seriously considering has completely rebuilt Detroit Diesel model 8 V 71 TI, V 8, two cycle, turbocharged 425 HP engines. This would be on a 58' YF. What do you all think of these engines in regards to reliability, predisposition to being a pain in the neck (AKA continual repairs and huge mechanic bills for me, the non-mechanic!)? What do you think is the "ideal" engine for a mid-70's 58 YF in regards to model and horse power?

Thanks for the input!

 

[Genesis]

That ain't a bad setup for those engines.... horsepower is pretty good...

If rebuilt correctly they should be fine...

 

[MikeP]

That's pretty much the standard package for a 53/58 from the mid 70's through the mid-80's. As far as I know, there wasn't any other engine option available. So if you're looking at one of those boats, those are the engines you are going to get.

As Karl said, if they're properly rebuilt and you maintain them, they should provide many years of good service. In fact, if you mostly run them in the 8-10 knot mode, they'll probably outlive you!

The bad thing about them is that they are totally mechanical and ancient technology; the nice thing about them is they are totally mechanical and ancient technology! They tend to leak oil, use more fuel, make more noise and smoke than do modern engines. In fact, a very old "definition" of a Detroit Diesel (when there were ONLY 2-stroke DDs) is: "A device for converting diesel fuel into large amounts of noise and smoke"

On the other hand, they will continue running under the most abysmal conditions and can usually be made to function with some really bad things wrong - things that would cause a current diesel's sensors and electronic wizardry to shut down and leave you somewhere you don't want to be.

They are very straghtforward and mechanically simple though they look imposing. This allows mechanics to charge a lot of money for doing poor work (oops, sorry. I was starting to digress). However, armed with a service manual and some decent tools, you might be surprised at how much work you can do yourself on these engines. And although you can certainly screw up an adjustment, it's hard to actually hurt anything.

Like any engine in the marine environment, you really do have to perform routine maintanance to avoid unexpected big bills. But this would be true of the most modern marine diesel as well.

And perhaps the best thing about them---they sound really cool!

 

[Woodsong]

assuming they were rebuilt properly and competently and that is combined with a well designed/implimented maintainence schedule, what would the typical lifespan be for these engines?

 

[SeaEric]

A few years back I purchased a project boat that had not been run much in 10 years or so. Power was a pair of 71 series ti's. With a mechanic onboard helping, we got her running and headed out of the basin for a quick seatrial.

It was December, cold, and getting dark out. I ran the boat from the flybridge. I became a bit worried when I realized we had ventured out on this beauty with non-functioning radio/depth finder, etc. I noticed among the bunch of gear that was useless, a perfectly good roll of duct tape. To which the mechanic remarked- "Relax! We got us a pair of Dee-troits and a roll of duct tape! We'll git home fer sure!"

 

[Genesis]

assuming they were rebuilt properly and competently and that is combined with a well designed/implimented maintainence schedule, what would the typical lifespan be for these engines?

Depends on how you run them.

IF, assuming you start with a properly rebuilt (or "new" motor):

1. You prop them to reach rated RPM + 50 with a FULL load.
AND
2. You do not allow them to EVER overheat (meaning, you keep the cooling systems properly maintained)
AND
3. You keep clean oil in them and feed them clean fuel; oil changes on 100 hour or less intervals.
AND
4. They're run often enough not to get internal corrosion going (every week or more often - not just started, but RUN so they are able to operate at normal operating temperatures for an hour or more)
AND
5. Your continuous cruise operation is at 350-400 RPM off WOT (e.g. 1900 - 1950) OR LESS, BUT at least high enough to keep them warm (e.g. 1000-1100 RPM)

THEN I would expect 3,000 or more hours out of them at this power rating.

Of course you might get more or less. But that would be my expectation. If you run literally every day you might do considerably better - 5,000 hours is not out of the question by any means.

BTW, it does not get much better than this with any high performance engine - no matter the make. I really like Detroits at rational power settings, and this is a rational power setting.

 

[captddis]

I will add a couple things also, A few of the high ticket items to look for on a older boat.
The exhaust system is pricey to replace . Look closely at the risers, collectors and blankets or hardcoating. Check the muffler for salt leaching and look at the mufflers and fiberglass tubing. If there is salt leaching around the connection, look at the top of the connection and see if the area under the clamps is flat at the top. Cracked tubing and mufflers is common, especially if some one cranked down on T bolt clamps.
The older My's had 2 piece shafts, the muff couplings are scarce. If there is a problem a new one piece shaft is usually needed. Also check shaft log hoses as they are a lot of labor to change.
Check the generator, a lot of them have been replaced. If so great if not it can be a problem later.
On the 53/58s that are run in rough water, the engine gets spray on it and rusted manifolds and sweep pipes result.
Hopefully the a/c units have been replaced if not, that can be a problem.
All the previous points on the engines are good. I will add that the original intercoolers are nearing the end and catastrofic engine failure can occur.
check if they have been replaced.
I know the question was about engines, but these are other considerations as well
Dave

 

[Woodsong]

captddis,
the boat I am specifically refering to is the one that you and I talked about on the phone...not the Med. Beach one, the other one....

my assumption (that needs to be verified) is that the engines on that boat were 100% rebuilt.

 

[MikeP]

Rebuilds can be done really badly so just having a rebuild doesn't mean it was any good. Talking to people who know the person/company that rebuilt the engine is a good thing. Do they have a good reputation? Obviously, if there's no paperwork, then you can't even prove that the rebuild took place anyway. An engine survey will give you a better idea of what's going on. BUT NOTE that a survey - no matter how thorough - can not give you any kind of "guarantee" that the motor won't blow up tomorrow!

There are a few people on this site who are not huge believers in engine surveys. I have to admit I'm one of them and have never employed an engine surveyor. HOWEVER unless you are very mechanical and have a good bit of experience with engines, a survey is worth the money from a "comfort" standpoint if nothing else.

Also beware of the spray-can rebuild! The typical giveway is all the painted or oversprayed wires and hoses and no paperwork.