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bennyd10 09-28-2008 09:32 AM

Can you run a Yanmar w/ turbo out?
I am looking at a boat that has a Yanmar JH4-TE Turbo 55HP engine in it. I was told that the turbo has been bypassed? This is because it is blown. They replaced the turbocharger once, but the oil cooler was not replaced and the turbo blew again... So then they bypassed the turbo and brought the boat from the Bahamas all the way up to N. Carolina. Should I be concerned???
Is the fact that the oil cooler is the problem cause the oil to burn and overheat? Would the turbo going out cause metal to enter crankcase oil? Sounds like it is not a good move, I am just wondering what damage could occur and how I can tell what all is wrong!!!

sailingdog 09-28-2008 09:43 AM

Why would someone be stupid enough to put a turbo diesel on a sailboat? It isn't like a sailboat is really the proper use environment for a turbo diesel. You really need to talk to a good diesel mechanic. If you're not going to use the turbo, you need to convert the engine back to a non-turbo setup IMHO.

SteveInMD 09-28-2008 10:06 AM

I believe you will continue to see turbos on smaller and smaller diesels for quite a while now. The really do wonderful things for efficiency and emissions. The down side is obviously there is on more system that can fail. However, despite this post, turbo failure rates have been greatly reduced in the last few years by improved technology.

If you've had two turbos die you most likely have an oil system problem (but it sounds like you already know this). You can run without a turbo, but I wouldn't expect the motor to preform well at all unless you make a whole number of changes including replacing injectors, and possibly the entire high pressure pump, and obviously the intake system, and the prop.

If it were my boat I would find and fix the oil system problem, replace the turbo, and then keep up with oil the changes.

timebandit 09-28-2008 12:10 PM

To start with your 55hp motor is only making about 35hp without the turbo.

I'm betting the boat came out of a rental fleet and the renters were not instructed to let the engine idle for awhile to cool the turbo down and prevent coking of the oil in the turbo.

Most turbos can be rebuilt for under 500 dollars.

I hope that the bypass was done in such a way that the parts are still there to reverse the procedure.

Let me know if you need the name of my rebuilder.


Kage2021 09-28-2008 02:45 PM

Before I comment I would like to offer this disclaimer: I have never worked on a marine engine, I have only recently gleened an interest in watercraft but I am an avid automobile enthusiast. At the very least have someone verify the following. I am only offering this to help because I do know quite a bit about turbos and all engines operate in the same basic manner.

That being said here's what I would assume/deduce in your situation.
Any engine built from the factory with a turbo is engineered with certain chateristics to deal with the turbo's additional psi. Physically this usually means higher quality parts to deal with the added pressure the turbo creates, as far as that goes it's a plus for you.

On the other hand, the engine is designed to run with the turbos added PSI. The engine will be running rich now that the turbo is gone. If you don't care about the loss of fuel economy I would think you would be alright on such a small engine. Another consideration is that most diesel engines simply compress air untill it's hot, then add fuel so it burns. Once agian, your engine will be designed to compress the air from the "intake" plus the additional air that the turbo would have compressed to reach firing temperature. If you feel that it is running fine, roll with it.

The only notes of caution I would offer you are the following.
1. Be sure who ever disabled the turbo did it correctly. Turbos are generally powered by exhaust fumes, if some jackass unhooked the turbo incorrectly you run the risk of building up exhaust fumes where they shouldn't be which is a fire risk.(especially considering the fact that your engine is running rich, your exhaust fumes are extra volatile)
2. It is possible (and probable) that the timing of the valves is slightly more aggressive than an engine w/o the turbo to maximize the efficency of the turbo, if this is the case at least you will have further decreased efficency, at worst you could ruin the engine. It's unlikely it's that bad, but if it is, you would deffinately be able to tell. It would run bad.
3. Turbos DO BLOW, BREAK UP, AND GET SUCKED BACK INTO THE ENGINE. You need to know if this happened. Drain the oil, get a magnet or something and see if you have metal particles in your oil. Take off the turbo, look at the blades, or make the person who disabled it instead of fixing it do it.
If it were me? I'd use this as a point to knock cash off the boat, change the oil twice over a short period, and ride it until I could fix the turbo. Chances are if the boat has ridden that far without any crazy problems, then all you need is to change the oil just in case.
Anyone want to add or adjust that feel free. I am only offering what I know in an attempt to help :)

Omatako 09-28-2008 03:34 PM

Here's my take on this:
  • The prime reason causing turbos to blow is that the rotor spins at a very high speed (as much as 30,000rpm) when under power. The spindle is supported by a film of oil pressure, not bearings. When the engine is turned off too soon after running at a significant RPM, the oil pressure disappears and the spindle, still spinning at a high speed, has no support causing it to seize.
  • It is possible that the poil cooler only serves to cool the turbo oil supply (which gets significantly hotter than the crankcase oil because the turbo body thru which the oil passes gets really hot) before returning it to the crankcase. It is also possible that the cooler is clogged with oil sludge (poor maint) and this is possibly why the second turbo blew as well.
  • When the spindle siezes the rotor touches the housing and the blades snap off. The exhaust blades are probably stuck in the exhaust mixer or water lift. The intake impeller will end up either sticking in the intake manifold or will go thru to the engine. If this had happened, there would some unwelcome noises coming from the engine.
  • Converting the engine to non-turbo has one expensive problem if it is to be done right. Turbo engines are designed with lower compression ratios than naturally aspirated engines with the turbo boost lifting the compression ratio to same-as or better with "charged" air. So without a turbo the compression ratio will be such that any tiredness in the engine over time will eventually make it imposible to start. You will also get sedentary performance at best - lazy, smokey and thirsty. The only way to overcome this is probably to replace the pistons and there may even be cylinder head variations so it could get really expensive.
  • The pump and injectors will probably have a slightly different spec but that's not a huge expense can be re-tipped and calibrated.
But I agree with SteveInMD, the efficiencies and benefits of small turbo diesels are considerable and if the old parts are still around, I would restore it to original. Even if they aren't it may still be the more affordable choice.

oldchief 09-28-2008 03:35 PM

Turbo's on diesel engines are generally extremely reliable. While they can fail, it is rare. Outside of some foreign object flying down the intake, the most common turbo killer is lack of oil or dirty oil.

Basically, you don't know what happened, and you can't rely on anyone else, so I would recommend that you find the best diesel mechanic you can afford and pay him about three hours labor to look it over. It is obvious that the previous owners took the cheep way out on the fix, and they probably took the cheep way out on everything else.

If you end up with this motor it will probably be cheaper to leave it as a turbo. Change the oil at least twice as often as the manufacturer’s recommendation. Everyone wants to extend the service intervals on engines, but it is a bad idea and the people that are recommending it do not own your engine or have to repair it.

Concerning an earlier post, the engine is not currently running rich due to lack of turbo pressure. Turbo boost comes on and off continually as the throttle position and RPM and load change. The fuel injection compensates for manifold pressure to keep the fuel to air ratio correct at all times, even when there is no additional boost provided by the turbo.

Good luck with this engine. Be very suspicious. It gives me the willies.

Rod Sorenson

Gryzio 09-28-2008 03:41 PM

Talk to a mechanic

Originally Posted by sailingdog (Post 376340)
You really need to talk to a good diesel mechanic. If you're not going to use the turbo, you need to convert the engine back to a non-turbo setup IMHO.

I will agree with SD on this. Ask around local to you. I am cautious of things when I not know the facts behind why it not work. Now, if the boat is priced like the engine not work, I not have a problem buying, if, it what I want. I not pay for a 1/2 running engine.
I did put a Turbo Charger on my 1966 Mustang back in the 70's and it worked and I assume it would work without the Turbo or disconnected. But, if the Turbo is blown and junk like that, then I would check the oil and filter for debris.
Also, I never buy something I can not fix. That not mean I will not pay for labor, but, I want to know what going on, then I know if I pay someone, I know what I paying them to do, not what they tell me. I can tell some stories about this; real mechanic rips if I were not educated.
This may help get you started.
HowStuffWorks "How Turbochargers Work"

BarryL 09-28-2008 05:05 PM

Hello Benny,

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.


Omatako 09-28-2008 08:40 PM


Originally Posted by BarryL (Post 376533)
just note that there is a huge difference between a gas turbo and a gas diesel, and an automotive engine and a marine engine.

1st question: What is a gas diesel?
2nd question: What is the difference between an automotive engine and a marine engine (other than the obvious marinisation)?


Originally Posted by BarryL (Post 376533)
If anyone is interested in some of the mis-information listed above, let me know and I will try and provide an accurate list.

3rd question: Why not provide the list here?

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