|Topic Review (Newest First)|
|09-29-2008 10:57 PM|
Thanks for the crash course in turbo diesels! I have talked to three or four mechanics and hired the one most recommended who owns the yanmar distributer in town. Sounds like this is the best course of action.
The crazy thing is, I went down to the boat with a mechanic today and got to fire the boat up and run it with him. It ran great! No blue smoke, no black smoke... ran it for a while, then ran it in gear at 2000 RPM... ran great. revved up to 2400, no black smoke.
The mechanic that I have hired for Thursday said that if the engine was run below the 2800 to 3500 range where the turbo "kicks in" then the fuel levels wouldn't be very much different, turbo or not. Another mechanic at the same shop just got finished telling me that the cylinders would be polished and wasted from carbon deposits after 10 to 15 hours of running without the turbo functioning. I guess it goes to show that there will be differing opinions on this... I am having the owner/mechanic at the yard come over and take a look in person and give me his opinion...
I also got to talk to a third party guy who was on the boat when they brought it back and he told me they were running 2200-2500 RPM's which has me hopeful that no major damage was done... I intend to replace the blown turbo unit if the engine seems sound. The mechanic said it would be cheaper/better to do this than to change out the engine to non-turbo. The main cost with this is the injection pump. I am not a mechanic and am passing this info on as accurately as I remember...
Sounds like the boat sails great in any case!!! We get to take it out on Wednesday! This is a Bayfield 36... I don't think I mentioned that.
|09-29-2008 10:00 PM|
If thye boat itself is what you want and is in good shape check it's fair market value IF IN GOOD CONDITION. Then offer that price LESS the cost of a new engine. That way you'll be covered and can afford to simply pull out that Yanmar and replace it.
Turbo diesels are great if properly maintained ... which this one clearly wasn't. If the maintenance was bad enough to blow two turbos it was probably bad enough to have caused some other damage as well.
If they don't take the deal, walk away and find another boat.
|09-29-2008 09:26 PM|
You know, I had written a long dissertation picking some of what BarryL said to bits but then I thought the better of turning this into a bun-fight. If you have an opinion that is different, Barry, then express it but (and once again ) I agree with Steve. . . . . .
Make a sweeping statement that "a lot of what has been said above is incorrect" and then providing the magnanimous offer of "If anyone is interested in some of the mis-information listed above, let me know and I will try and provide an accurate list", you're going to elicit a response from me, for sure.
And for the record Barry, a few points on your last so-called "accurate list" are questionable so try to avoid having people put you on their "ignore" list - have some respect.
Sometimes it's good to listen to what others have to say - it allows you to understand the true depth of your own knowledge (or lack thereof!).
And the response "go find a decent mechanic" would actually be correct for every mechanical thread posted here so we could all save a huge amount of superfluous chatter by issuing one-line responses. But geez, would it make this forum boring.
|09-29-2008 01:14 PM|
|SteveInMD||I agree in this is a job for a good mechanic. I take issue with the statement that everything everyone else has posted is rubbish. The goal here is to help the OP understand why a mechanic is required in this case.|
|09-29-2008 12:14 PM|
Given the OP's question, it is rather obvious that the background isn't in engine repair.
This isn't a bad thing, may just not be the OP's cup of tea...
The responder that responded "have a mechanic fix it", was probably more spot on that trying to de-cipher system internals of a turbo vs. non-turbo.
I'm suprised that it ran at all.
If it did, I'll bet it was smokin' like a chimney, and had the power of a one armed kayaker.
Many items are different. this ain't a 5.0 mustang, where you can buy a "kit" for 1500.00 outta the back of a jcwhitney catalog.
IF there is a non turbo version of the same engine, pistons, rods, head, valves, cam, fuel system, and exhaust system will be different. Cooling too. Lube systems too. Possibly main and rod bearings... the list goes on. It might not even have the same block. (wet vs dry sleeves, oil passages, yadda, yadda, yadda)
Just saying "have a mechanic look at it" ... period....
is probably the best advise that I've seen on this thread.
the old man used to say... "If i have to take the time to explain it to ya, you can't afford to fix it."
Originally Posted by SteveInMD View Post
|09-29-2008 10:19 AM|
|tweitz||By the way, I would not rely too much on the fact that he brought it from the Bahamas to North Carolina unless you know more about the trip. It is a sailboat. He may have barely used the engine.|
|09-29-2008 07:56 AM|
|SteveInMD||If you're going to trash out everyone's advice, it would be helpful to say more than to have a mechanic fix it. I agree the fuel map will be out, hence the need to replace the injection pump and injectors, since there's no computer control unit to adjust the map. The power produced by the motor will not be the same, hence the need for a new prop (or pitch adjustment). Other changes that may need to be made are cams, intakes, and exhaust systems.|
|09-28-2008 10:24 PM|
Originally Posted by Omatako View Post
Gasoline engines are quite different than diesel engines. A gas engine runs at a much lower compression than a diesel engine. A turbocharged diesel engine has a LOT more pressure than a normally aspirated diesel engine. Generally, the higher the compression, the more important it is to accurate control timing, both spark (for gasoline) and valve (both diesel and gas).
Four stroke internal combustion engines, whether gasoline, diesel, alcohol, turbocharged or normally aspirated, all operate pretty much the same. The difference is in the typical use.
For an automotive engine, the typical use is various RPM and load, very rarely running at high load conditions for extended periods of time. A turbocharged automotive engine uses the turbocharger for short periods of high power output. For most of the engine use, such as highway driving, or around town driving, the turbocharger is not producing any power, or putting any load on the engine. When the engine is subject to high load conditions, such as hard acceleration, power to pull a heavy load, or climb a hill, the turbocharger will spin up, provide the extra power, then spin down for more typical highway type cruising.
The typical use of a marine engine is much different. For a boat that is heading from point A to point B, the engine is started in the morning, the transmission placed in forward, the throttle moved to cruising speed, and the engine will then operate at mostly a constant RPM and load. A boat has no hills to climb, stop lights to wait at, or other cars to pass. The turbocharger in a marine engine will be under load the entire time. The turbocharger puts a significant load on the engine, which requires additional maintenance.
Other significant differences between automotive engines and typical marine diesel engines is in engine management. All modern automotive engines are computer controlled. There are sensors for throttle position, engine temperature, exhaust, RPM, ignition, etc. The computer runs the engine in closed loop, constantly adjusting the amount of fuel injected to ensure the engine is running properly, not too rich or to lean. Turbocharged engines, when the turbo is producing power, are intentionally set to run rich. The extra fuel helps to cool the combustion chamber. As soon as the extra load is removed, the engine reverts to running lean for economy.
Marine engines (at least the ones that I am familiar with, which are small auxiliary engines for sail boats) are quite primitive. The fuel injection is mechanical, and there are no sensors to monitor engine performance. Since the marine engine operates in a relatively narrow range, it is easy for the manufacturer to dial in the fuel injection curve so you get adequate performance over the RPM range. A turbocharger requires a different fuel injection map. If you just remove the turbo, without changing anything else, the fuel map is going to be off.
That's about all I have time for now.
Let me know if there are any additional questions.
|09-28-2008 09:40 PM|
Originally Posted by BarryL View Post
2nd question: What is the difference between an automotive engine and a marine engine (other than the obvious marinisation)?
Originally Posted by BarryL View Post
|09-28-2008 06:05 PM|
Good luck with this engine. There is a lot of information listed above, most is not correct. I am not going to review the info above, just note that there is a huge difference between a gas turbo and a gas diesel, and an automotive engine and a marine engine.
If you are serious about this boat, the best advice has already been given to you: Hire a good diesel mechanic and have him perform a thorough analysis of the engine. The engine may be fine, it also may have serious and expensive problems.
If anyone is interested in some of the mis-information listed above, let me know and I will try and provide an accurate list.
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