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Old 30-03-2014, 15:40   #1
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Hours unknown...

Hello guys,

There is a boat that I'm interested in. The broker says that the odometer hours don't match the dashboard hours for the engines. He says that the owner has no knowledge of what the actual hours are and the previous owner has no info either. They also don't have any information if the engines have been rebuilt or not. I thought this was strange.

I'm wondering if a mechanical inspection can tell me if the engines are good despite having no history or if I should not consider this boat at all because of the discrepancy and lack of info?

Can a neglected engine become a good engine with a rebuild or can a bad engine not be rebuilt at all?
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Old 30-03-2014, 15:44   #2
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Re: Hours unknown...

You need to find yourself a good buyer's broker who will work on your side... Someone reputable with knowledge in the marine industry who can answer questions as they come up and steer you away from the turkeys.
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Old 30-03-2014, 16:04   #3
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Re: Hours unknown...

What engines, how old, turbo or naturals ? ... it make a difference to your questions.
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Old 30-03-2014, 16:08   #4
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Re: Hours unknown...

Quote:
Originally Posted by Kenomac View Post
You need to find yourself a good buyer's broker who will work on your side... Someone reputable with knowledge in the marine industry who can answer questions as they come up and steer you away from the turkeys.
Fair statement. Well taken. But...

Even if I did have a good broker, I would probably still ask the questions here. I'm not that trusting of brokers, not even the "good" ones. Guess my years in RE have tarnished me. Brokers only get paid when they sell something.
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Old 30-03-2014, 16:16   #5
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Re: Hours unknown...

If you go to survey get an ENGINE SURVEY by a mechanic, and a sea trial under LOAD.
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Old 30-03-2014, 16:33   #6
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Re: Hours unknown...

Is there much of a difference between the two meters? I would probably just assume the higher to be right. A engine survey will be needed.
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Old 30-03-2014, 17:05   #7
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Re: Hours unknown...

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Originally Posted by boatpoker View Post
What engines, how old, turbo or naturals ? ... it make a difference to your questions.
12V71 Detroits

I don't think they are turbos. Turbos are ti, right?
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Old 30-03-2014, 17:59   #8
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Re: Hours unknown...

GG if boat is otherwise what you need and in good general condition the motor issue can be resolved by a good mechanical survey. Not all mechanics are created equal or have the same knowledge banks. So your job will be to do the research and find a competent motor surveyor (not same as boat survey) who is working for YOU(from RE you know what I mean) and familiar with the particular motors in question. Those old diesels are often noisy smoky, and messy but they can go a long way and are rebuild-able.
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Old 30-03-2014, 18:46   #9
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Re: Hours unknown...

GG, There has to be a Detroit Dealer near by! Get a COMPETANT mechanic to ck the motors out! Be carefull of the 12-71s Great engines if well maintained, and as said they are rebildable, But they are fuel hogs LOL, They have been in the past a pretty standard Commercial fishing boat motor ! And have good reviews from that useage! But remember that they are a NOISE Maker !! Make sure that the noise don't bother you or your family when your useing the boat ! just a few thoughts
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Old 30-03-2014, 18:50   #10
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Re: Hours unknown...

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NOISE Maker !!
Hence the nickname Screamin Jimmy.
Aka, the driptroit diesel.

Easy to rebuild and robust motors, get the Detroit guy as suggested, they will know enough to give you an honest as possible analysis.
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Old 30-03-2014, 19:51   #11
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Re: Hours unknown...

Here's a thread with some good info... Detroit Diesel Question?
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Old 30-03-2014, 20:09   #12
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Re: Hours unknown...

Great motors.Will burn close to 90 gallons an hour WOT.I say go for it.Those motors sound fantastic.

Sent from my SAMSUNG-SGH-I747 using Cruisers Sailing Forum mobile app
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Old 30-03-2014, 20:34   #13
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Re: Hours unknown...

Quote:
Originally Posted by GalaxyGirl View Post
Hello guys,

There is a boat that I'm interested in. The broker says that the odometer hours don't match the dashboard hours for the engines. He says that the owner has no knowledge of what the actual hours are and the previous owner has no info either. They also don't have any information if the engines have been rebuilt or not. I thought this was strange.

I'm wondering if a mechanical inspection can tell me if the engines are good despite having no history or if I should not consider this boat at all because of the discrepancy and lack of info?

Can a neglected engine become a good engine with a rebuild or can a bad engine not be rebuilt at all?
Is the engine hour meter mechanically driven and the dashboard electrically driven? I know on small airplanes that the mechanical hour meter can run 70% of the actual time of flight, like doing touch and go landing practice where some is just gliding. What I would do is see if either hour meter is actually working and go with the working one if there is one.

I would be more concerned with the horsepower the engine is rated at for its displacement. A diesel engine of a given displacement, which is how much air all the cylinders can take in when the engine goes around once, can have a range of horsepower ratings depending on how big the fuel injectors are. The bigger the injector, the more horsepower; however, more power means accelerated wear, lots of cylinder wear. A compression test will tell something about that as will engine oil analysis on use oil. The marine pleasure craft application has the most wear and here are the specifications for that:
http://www.detroitdieselpartsdirect....sure-Craft.pdf These graphs are for turbocharged engines. The graph to the left is for maximum power, the one on the right for much longer engine life. Take a look at the graphs and note the gallons of diesel used per hour vs. the engine speed or revolutions per minute (RPM) when a fixed pitch propeller is used. Very few boats have propellers that have an adjustable pitch because of the cost, although tugboats use them because of the improved fuel economy. The graphs are a bit confusing because it shows horsepower over a range of RPM for rated brake horsepower (BHP) and just below that rated shaft horsepower (SHP), which is with accessories, and right under that is propeller horsepower. Propeller horsepower falls off quickly for lower RPM because a propeller cannot absorb the power that is there. It is sort of like the tires on a car spinning on ice. Unlike ice though, increased RPM does result in better 'tire traction'.

If the same displacement engine is being used for normal marine use with longer life required, the horsepower is less than for marine pleasure craft: http://www.detroitdieselpartsdirect....1TI-Marine.pdf. Note that there are power specifications for Continuous, Intermittent, and maximum power and the each specification has a different size injector to limit the amount of horsepower dependent on power specification.

The 12V71 engines are rebuildable. The cylinders and pistons are removed and new ones are installed along with new bearings and other items. There are engine kits that supply all the necessary parts. Detroit parts are less expensive than most other manufacturers. Check on ebay or even Amazon. Of course you need a mechanic to put it all together. An automotive machine shop that specializes in diesels could do the job. The 12V71 was used in 18 wheeler over the road trucks and is common. It was a very smooth running engine in a truck, but had lots of noise. This noise can bother some power boaters. Also, these Detroit 2 cycle engines do not give as much power per gallon (specific fuel consumption) as 4 cycle engines like Cummins diesels. Detroit is the only 2 cycle engine in boats. In ships there are 2 cycle engines, but these are massive, low RPM, and run on residual oils that are much heavier fuel than diesel.

The two turbocharged engines have ten times the horsepower that is needed for cruise with a displacement hull. One engine that is not turbocharged would be about the right size for a trawler, a boat without a hull that can plane. A boat that gets up on top of the water and moves at say 18 knots is up on plane, but range is limited because these boats have to be light and too much diesel for long range cruse would weigh so much and the boat could not plane. Note that a boat that planes has a much greater fuel consumption and limited engine life, maybe as little as 500 hours if the boat is run full power most of the time.
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Old 30-03-2014, 23:29   #14
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Re: Hours unknown...

Do the marine detroits have the same oil leaking issues as the highway detroits? Series 60 I believe or the older mechinacial. If it was leaking oil yep it has enough oil in her.

wondering around with no destionation
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Old 31-03-2014, 06:09   #15
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Re: Hours unknown...

Quote:
Originally Posted by GalaxyGirl View Post
Hello guys,

There is a boat that I'm interested in. The broker says that the odometer hours don't match the dashboard hours for the engines. He says that the owner has no knowledge of what the actual hours are and the previous owner has no info either. They also don't have any information if the engines have been rebuilt or not. I thought this was strange.

I'm wondering if a mechanical inspection can tell me if the engines are good despite having no history or if I should not consider this boat at all because of the discrepancy and lack of info?

Can a neglected engine become a good engine with a rebuild or can a bad engine not be rebuilt at all?

By "odometer" hours, you mean a engine mounted hour meters? If so, do they exceed hours on the dash-mounted meters? If so, I'd tend to believe them more likely than the dash-mounted meters. When dash-mounted tachs with hour meters are replaced, for example, the hour meters aren't usually reset to reflect actual current engine hours.

If these are engine mounted hour meters, do they roughly match in hours? If so, they might suggest not rebuilds... or maybe both engines were rebuilt.... at roughly the same time. (Although I'm not sure how engine-mounted meters work; not sure they'd be reset at a rebuild or not. Our engines don't have on-engine meters, so I don't have much experience with those.)

A good mechanical survey (i.e., an engine survey, in this case, performed by a good DD guy) can tell you how to proceed. (Have him look over the genset(s), too, while he's at it.)

DD 12v71s have a good reputation, assuming your surveyor finds no showstoppers.

-Chris
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