Why So Many Boats with Rebuilt / New Engines ?

[headhertz]

I've been trolling the boat classifieds and it seems to me, once an auto mechanic with a decade of experience, that there are far too many boats on the market that advertise rebuilt/new engines.

There must be a reason for this. I suspect that most boats engines never get the use that a car gets in 100k miles (2000 hours seems like a conservative estimate for a mostly highway-miles equivalent). I'd be upset with an engine in my car that didn't last 200k miles before needing an overhaul. I've little experience with diesels but if the local ranchers are to be believed a person should expect much more from a diesel.

I wonder if something is hard on the engines like motoring just far enough to get out of the dock rarely giving the engine a work out, or open-loop cooling systems having temperature extremes or blockages, or lack of maintenance because they are hard to access...

Any ideas?

[familycruisers]

Is say you hit most of the highlights. Diesels need/like to be run.

[SkiprJohn]

Your third paragraph pretty much sums it up. Operator error is the reason that some don't get 5000 to 10,000 hours. The better diesels are designed to last a very long time with many hours of operation. I've sailed aboard boats that have the same diesel engine it came with more than 30 years earlier so they'll last if the operators give them a chance.
kind regards,

[Cheechako]

I think you are pretty much spot on. also, some boats rarely get run the last couple of years before theyre sold. also, you might find when you investigate a boat that has a New or "recent" engine some more, it will come out something like: " the guy I bought it from 2 years ago was a mechanic and he rebuilt it"............ uh hmmm....

[FSMike]

Consider the environment the different engines live in. If you have a cooling system problem on your car engine you just fix it and keep driving. A similar problem on a boat could result in a salt water bath for various moving parts that would become unhappy.

[Rakuflames]

Originally Posted by headhertz

I've been trolling the boat classifieds and it seems to me, once an auto mechanic with a decade of experience, that there are far too many boats on the market that advertise rebuilt/new engines.

There must be a reason for this. I suspect that most boats engines never get the use that a car gets in 100k miles (2000 hours seems like a conservative estimate for a mostly highway-miles equivalent). I'd be upset with an engine in my car that didn't last 200k miles before needing an overhaul. I've little experience with diesels but if the local ranchers are to be believed a person should expect much more from a diesel.

I wonder if something is hard on the engines like motoring just far enough to get out of the dock rarely giving the engine a work out, or open-loop cooling systems having temperature extremes or blockages, or lack of maintenance because they are hard to access...

Any ideas?

In my case, we pulled one of the zincs out of the salt water cooled engine to find that it was worn down to a nub. I don't even know how long it was like that, but since that zinc was far more easily changed than -- say -- the oil, I seriously doubt that engine was well taken care of.

You really did have to be a contortionist to change the oil on that engine. I have other signs that the previous owner just wasn't sensible about maintenance, and I doubt he changed the oil very often.

The new engine is much easier to take care of. The oil access is right in front, and you don't have to remove the water pump to change the impeller. But in spite of that, a 1983 salt-water cooled engine lasted until 2011. Maybe an engine can only survive salt water for so long. I made a list of 20 things tried before I replaced that engine. The next step would have been to remove the head and start doing some serious exploration. I read up on that and found pretty consistently that once you start doing that in an old, salt water cooled engine, internal parts start breaking, and that very often they simply could not be rebullt.

If you're looking at an older hull with a newer engine that really is a selling point. Take it from someone who didn't hold out for that.

[Kindle]

"rebuilt", particularly in a classified add, doesn't always mean "rebuilt" it might mean as little as a repair or maintenance has been performed.

[Dennis.G]

Truth be told, for 90% of sailboats, they would be much better served by a gasoline engine. I know the safety advantages to diesel in a boat, but think of the average sailboat engine operation: Start it up, motor out of the slip into the bay, shut engine down and go for a sail. Same routine at end of day. What, a half hour or less of low speed motoring? Or then starting the engine up at anchor to charge the batteries (at maybe a fast idle)?

Running long miles under engine is not the problem, it is all these low load and short duration uses that kill a diesel. A gasoline engine would really handle most of these tasks better. If running 72+ hours straight, diesel would be ideal, if running less than 1/2 hour or low loads, gasoline better. The fact is that almost all sailboats built since the 70's have diesel however.

Of course I have a diesel and would not replace it with a gasoline engine

[headhertz]

I think if I were designing a boat I would spec an air-cooled or closed-loop cooling system and solve half of my problems right there.

That probably only means that there is something significant that I don't understand and leads the actual designers to a different conclusion.

Thanks for the input.

[Sand crab]

Also.... those diesels are very expensive at around $200 to $400 per 1 horsepower new including removal and re-installation and the inevitable extras. So a 50 HP could cost you $10,000 to $20,000. A new engine is usually a good thing. MY 2 cents. BOB

[O.C.Diver]

Consider this:

I'm close to buying a used trawler. The ones I'm considering all have single engines 18 to 30 years old. You really don't know the condition of the engine unless you rebuild or replace it. If I'm half way down the ICW and my engine dies, I'm at the mercy of some boat yard and who knows what premium I will have to pay. Then there is the lost vacation time issue. Pretty much plan on rebuilding or repowering anything I buy. With that you get peace of mind, maybe better fuel efficiency, and a current production motor with readily available parts. Think how confident you are about your engine next time you are motoring through a tough inlet in a big following sea with an out going tide. When the engine quits in your car, you become a pedestrian. When your boat engine quits in the inlet, you will wish you were a pedestrian! There are probably lots of people who have rebuilt or repowered a used boat that they purchased because of the perceived or unknown condition of the engine.

I run a single engine charter boat for a living. If I wait till the engine quits before I rebuild it, 6 lost days of charters equals the cost of my last rebuild. Good rebuilds take weeks not days.

Ted

[martinjrichter]

I owned a trucking company and had a Cummins 600 diesel 1850 ft Lbs torque. This same engine is used in quite a few power boats.

That engine would run 650,000 miles before a rebuild was needed. So I estimate that is 12,000 hours plus any idle time. Most long haul trucks idle 12 hrs a day while on the road, another 13100 hrs before the overhaul. Total 25,100 hr operating time.

From my experience ( 10 years over the road) most truck repairs are for stuff other than the basic engine, A/C units, alternators, water pumps and the like. Older engines often had injector and pressure pump problems, but with the new computerized units that is a thing of the past.

BTW Cummins specifies the oil changes at 20,000 miles or 3640 hrs intervals (13 gal oil and two filters). I just did it once a month when I went home.

[Chief Engineer]

The third paragraph is spot on.

[SteveT]

For those talking about diesel longevity firstly I would say - read the manual and operate / service it as required! Also salt water is very hard on any machinery so you really need to try and keep the salt away from the engine which unfortunately is not always possible. Another factor in short lived diesels is fuel quality - in some parts of the world it is quite difficult to get good quality and clean diesel on a dockside fuel berth. Our (Yanmar) diesel is easily maintained and just chugs along. Of course where we sail every time we go out / come back we are usually running the engine at 80% load for several hours - strong tidal streams with locking-in times critical do not make for purist sailing all the way.

[DaveOnCudjoe]

There was a time, not so far past, that IT stood for Industrial Technology. So few people understand the needs and requirements of internal combustion engines and their fuel and load constraints that it's no wonder they fail at premature rates. Something as simple as propeller size and exhaust gas temperature can spell doom to valves and pistons. All old engines I've seen have alarms and multiple gauges to monitor function. Dave