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Old 13-02-2010, 07:23   #1
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Repower vs Rebuild: Which, and Why?

Seems I see a lot of boat postings where it has been repowered with a different engine than orginal. But see a lot less of ones that have rebuilt the orginal engine. Why would this be? Seems it would always be a lot more time and expense to repower and change the mount etc than do a rebuild.
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Old 13-02-2010, 07:43   #2
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There are reasons to do either one including the cost difference that you mention. The biggest reason in my mind to repower is that the current engine does not do what you want it to. This could mean that it is underpowered, hard to get parts for, noisy, smelly, heavy, etc. The disadvantages of a repower are cost and the effort required to redo all the peripheral systems.

The major reasons to rebuild are cost, ease of doing, the fact that you already know the engine, etc. The disadvantages are that you have an older engine which isn't as refined and that there are some parts that fatigue that do not get replaced in a rebuild (this really isn't a problem at all).

Traditionally, larger engines have gotten rebuilt and smaller engines get replaced. The cost difference is much greater for large engines and they are often installed so that they can be rebuilt in place.

If your current engine works well for you and you can find a good rebuilder nearby, it is a very good option.
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Old 13-02-2010, 07:45   #3
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Pros and cons to both options. A few that occur off the top of my head after having done one of each option.

Rebuild

1. often cheaper
2. use existing everthing: trans, engine bed, hoses, fittings, etc
3. usually older design (may be plus or minus, depending)
4. how well do you know/trust the rebuilder
5. depending on level of overhaul, engine design and space might be able to do without hauling the engine.

Replace
1. newer technology so could be quieter, lighter, more fuel efficient, etc
2. new warranty
3. may require extensive mods to install, new trans, new beds, mounts, etc.
4. usually costs more
5. may require serious carpentry to make room to remove old engine and install the new
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Old 13-02-2010, 08:07   #4
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I replaced mine.
Since I was doing a major refit and replacing reconfiguring pretty much every thing associated with the engine and since I believed that the newer one would be more efficient....I figured it would be the way to go.
I hope I never sell my boat but if I do....this engine will add value where as the one from 1978 would have taken value away...rebuilt or not...I think.
Also, not having a reputable shop to rebuild the old one figured into my decision.
Having said all that...It was a bigger job than I expected, and did take considerable more time...in my case a war broke out and I was unable to get my boat out of town....had I rebuilt it, it would have been done much earlier and I could have gotten the hell out of Dodge!
As it turned out the gods were with me and I had no damage....not to the boat...cant say the same about my nerves worrying about her!!
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Old 13-02-2010, 08:49   #5
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I repowered since I was doing a complete refit. It seemed that starting with a blank slate and putting the engine I wanted (quieter, more fuel efficient) with the corresponding electrical upgrades would be the best way to assure I had everything I wanted and assure it was done to my specs. In reality it was harder then expected (or estimated) and I spent more then I would have doing the same thing with the old engine. But now I have an engine that I know from birth and if I screw it up it is all my fault.

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Old 13-02-2010, 09:04   #6
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When I made the calculation it seemed that repowering would turn out cheaper. This was because of the parts of the engine that don't get rebuilt. The starter the water pump etc. I figured if one or two of those went out then I was at the same cost for rebuilding a Yanmar 4JHE. I also was able to get the latest iteration of that engine which has some nice features.
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Old 13-02-2010, 09:17   #7
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If either you did the work, or had a mechanic do it, wouldn't you know a rebuilt engine just as well as a replacement model? As far as parts go, seems for the price difference you could easily be able to buy common replacement parts to have (if long term cruising you need those anyway). I just have a hard time believing in the "want to be able to trust in" agruement sometimes given; seems if you got 20 years out an orginal engine before needing a rebuild you should belive in the engine. Efficency seems like a 20 year plus pay back for the extra cost (if you motor a lot). Noise seems like it would be less to upgrade your sound insulation.

If you repower because the orginal is just unpowered for you, well I can see that one I guess. But seems it would have had to be a real big problem to justify the cost for this (it should have been kind of apparent when you got the boat that it was under powered).

I wonder if the real reason is that people LIKE to have new instead of rebuilt. In other words it has nothing to do with anything other than emotion.
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Old 13-02-2010, 09:30   #8
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Don,

I agree that you will know a rebuilt engine at least as well. Unfortunately, there are occasionally horror stories of a bad engine rebuilder but it is not rocket science and there are some very reputable rebuilders around. From the standpoint of working on the engine, a rebuilt one is often better because you have previous experience with it and older engines tend to be a lot simpler and have no electronics.

Cost wise, a rebuilt will come out ahead for most people. It takes a lot of motoring to make up the difference in cost with fuel. If you assume that a new engine is $5k more expensive (what it would be for my boat) by the time you are done and that it is 10% more fuel efficient with fuel at $4/gal, it will take 1250 gallons saved to pay back the cost difference. This would mean 12500 gallons burned in the engine which on many of these smaller engines exceeds their life so there is no payback. Unfortunately, you don't recoup much of the cost of a repower during the sale of the boat, you might get a little but as long as it has a working engine, the value is pretty much constant.

The reasons that I see for doing a repower are comfort driven (noise, vibration) and the ability to find parts.
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Old 13-02-2010, 14:48   #9
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Toil and trouble...

After looking at all the problems involved with pulling an engine out my feeling was that I never wanted to do it again, so I went for a new John Deere 4045/ZF63.

Also I could not find a reliable source of parts for the old worn out Ford 2402E mated to an old Kazaki gearbox that did not go into gear properly.

The difference in price between a rebuild and new meant it just was not worth the risk.
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Old 13-02-2010, 15:49   #10
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Quote:
Originally Posted by Don Lucas View Post
seems if you got 20 years out an orginal engine before needing a rebuild you should belive in the engine.
...
I wonder if the real reason is that people LIKE to have new instead of rebuilt. In other words it has nothing to do with anything other than emotion.
If "you" got 20 years out of the engine you might feel better about rebuilding. If you bought someone else's engine with who knows what type of treatment then you may feel less confident.
As far as the second part I just have to say "Duh". Who wouldn't LIKE a new anything rather then an old one given the choice. You can make the same argument about cars and yet there are many who buy new knowing they take the hit monetarily. I see a lot of sailors who overdo anchors, chains, hull thickness, hull material, electronics, you name it, for the sake of "sleeping more peacefully at night." Buying a new engine vs a rebuild may fit right in that meme

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Old 13-02-2010, 15:56   #11
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For me its rebuild all the way. When I used to drive I had the same engine that wore out 3 vehicles, went over 500000 mi and ran like a top when I sold the camaro it was in. I rebuilt the engine every time I pulled it. The perkins in my boat has already been 34 years and still holds steady 60 lbs oil pressure and doesn't use oil. I have plans to dry out the hull and have decided what better time to tear her down and tighten up the clearances. The wear items get replaced regularly and won't be needed in long block rebuild. IE..starter, raw water, exhaust riser and manifold,heat exchanger, hoses,etc. A simple rebuild will cost around 1k. Add 400 for trans rebuild. Another 400 for propshaft service. Not even close to cost of repower. I rebuilt my first engine 30 years ago and can't see a reason for throwing away a block unless its cracked or otherwise unserviceable. I've never understood todays throwaway society.
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Old 13-02-2010, 16:18   #12
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Originally Posted by forsailbyowner View Post
A simple rebuild will cost around 1k. Add 400 for trans rebuild. Another 400 for propshaft service. Not even close to cost of repower. I rebuilt my first engine 30 years ago and can't see a reason for throwing away a block unless its cracked or otherwise unserviceable. I've never understood todays throwaway society.
Well for starters it is a significant minority of boaters that could actually rebuild an engine satisfactorily so if you have that talent with diesel engines you have a skill that will save you money that others don't have.

Also, it cost me almost as much as you planned for your rebuild to get someone to rebuild just my fuel pump and that is with 3 estimates and about 3 weeks to do it. Most places were looking at closer to $6500+ for a rebuild of the engine, so again, doing things yourself can make a big difference, but for those without that ability we are at the mercy of the market.

I would love to get that type of comfort with my diesel engine but I am afraid it will take a lot more time away from sailing to get that deep into the workings. I am going to stick to replacing parts that I can replace and save some of the kitty for engine work and hope I can find folks like you when I need them

Jim
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Old 13-02-2010, 16:18   #13
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Very good discussion! As a rebuilder who also sells new engines, I feel each decision must be considered carefully. Before I left SoCal in 1988 to go cruising, I intended to rebuild my Perkins 4-236, however, I found a new 4-236 for a great price, so made that decision. 22 years later and 3,500 hours, she is just broke in. I would definitely rebuild my Perkins. I have an older Yanmar powering my generator with over 6,000 hours on it. It still runs great, so ...
I have specialized in the venerable Universal Atomic 4, gas powered "Old Flat Head". Guess you know here my call sign comes from. My completely rebuilt A4's sell for around $3,000. My least expensive same footprint diesel sells for $8,500. So I ask a lot of questions:
Where are you going? How long are you going to keep the boat? Do you mind doing a little maintenance? Are you concerned with noise, smell and/or vibration? ETC

$$$ are a major issue. Look at $8500 and $3000. That is $5,500. We have spent an entire year on our Cal 46 in Mexico for a little over that.

As for rebuilds, there are some engines I consider not worth the expense. Farymans, Volvos, some newer Yanmars, some of the GM V-8 diesel marinized. I will discuss the pros and cons, off the forum, since I have been warned not to speak ill of the "Green Grief" or I would face litigation.

Keep the dry side up and wind abaft the beam.
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Old 13-02-2010, 19:38   #14
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Another point to weigh in a decision. One disadvantage to new Diesels is the electronics that are involved in running. An old Diesel won't be taken out by a near lightning strike, but apparently some new ones can be.
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Old 13-02-2010, 21:07   #15
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almost all modern electronically controlled diesels have a reduced running spped where the ECU fails. Anyway its an electronic future as, in practice diesels need electronc controls to meet current and forthcoming emmisions controls
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