Need a mechanics help!

[maxtorque]

Have found this forum very useful in the past, and now need assistance with some sound mechanical help:

I own a Sealine S240. The engine is a 3.7ltr Turbo charged diesel 370 STI Yamaha with outdrive.

Symptoms:
Over the last few outings the temp has started to creep to slightly higher (normal) readings, not in the red, but well past its usual setting of slightly above mid way.

I am losing a good 10kts off my speed, used to pull well from about 15kts up to 30+kts, now only manages a measly 15kts+.

Today, when I throttled up (houston!), the engine made a very loud "whish" sound directly related to throttle setting and only when I selecte full power or thereabouts. If I throttle back, the sound disappears.

When I hooked up to my mooring and looked at the engine in detail, I found that one of the hoses coming from the heat exchanger didn't have any water in it even though the freshwater tank was full of coolant! [and other related hoses were full of coolant.]

The Turbo housing seemed very hot!!!

Am I paranoid or could it be that the thermostat refuses to open, thus not allowing water thru to the turbine housing, and now my turbo has BLOWN????

Will I wake up soon and find my hot water bottle is leaking???


Your thoughts and advice would be most appreciated.

This is going to cost me dearly isn't it?????

Thanks









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[markc]

any smoke? If so what colour?

M

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[maxtorque]

If I throttle back quickly, and very rarely, there is a little black smoke..I was told this occasionally happens with diesels after a run.

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[muchy_]

"This is going to cost me dearly isn't it????"

Goes without saying really doesn't it ;-)

Maybe the water pump? (engine one, not raw one).

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[markc]

I would guess at two things...

1 Fuel starvation
2 Weedy bottom or fouled prop

Could it be either?

M

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[maxtorque]

Mark: weedy bottom...rather personal eh? Actually, there is quite a bit developing down there, but wouldn't account for the noise from the engine or the lack of coolant on the hose would it?

Fuel starvation: I think with that, the revs wouldn't pick up, and I'm getting the full rev range.

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[maxtorque]

maybe the fresh water pump...didn't think of that, but would that cause the almighty 'whish' or 'hissing' sound every time I throttle up, and if the pump was duff would the temp gauge indicate in the red?

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[maxtorque]

maybe the fresh water pump...didn't think of that, but would that cause the almighty 'whish' or 'hissing' sound every time I throttle up, and if the pump was duff would the temp gauge not indicate in the red?

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[Col]

Are you sure that the water pipe isn't in fact a turbo intercooler pipe?That would explain the wooshing noise ( and why no water in pipe although header tank full) and the loss of power.

Basically you have the turbo, the intercooler, and the air filter all linked with hoses approx 1 1/2" dia. Suggest you look for a split or disconnected turbo hose.

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[banus]

I agree with the split air pipe theory. That explains the whooooosh, the lack of power and the overheating. Also look for a pipe collapsing. Get someone to give it full throttle (must be under load) while you look in the engine bay. If it was the turbo you would get lots of white smoke

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[markc]

If this was the case, surely there would be black smoke as the turbo would not be able to supply enough air for combustion?

M

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[Solitaire]

Not sure of how much use this will be, but I've just re engined my Sprint with the same engine as yours. The work was done by BBMS services who are Yamaha dealers. Despite issues I won't go into here, the work has been done well. Bill Brown used to work for Yamaha and knows them inside out. If you would like his number PM me.
On another issue, what size prop are you running on your Sealine? I inherited the prop on mine with the leg and I'm not getting the top speed you are. Our boats are about the same size and weight and it would help me to know the best option. Many thanks.

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[markc]

Firstly, turbos do 'woosh' anyway - has it got worse? Also, if weedy bottom then you will be running the engine much harder and perhaps the labouring is causing the high temperature?

There is also no tell-tale smoke - if you had blown a turbo pipe in a major way then you would have loads of black smoke. However, always tough to form a good opinion without being there!

M

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[nickjaxe]

As a truck driver on heavy trucks, if it helps, I can confirm if the pipe from the turbo to intercooler is split or holed in any way, you will get a wooshing sound from escaping air and lack of power from the engine.

Nick in cheshire.

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[maxtorque]

Thanks very much to all so far. I will PM some and carry out further investigation in areas recommended by others. What would we do without this forum?

Thanks gentlemen

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[Russell]

I'm not sure you would get the black smoke if the turbo pipe is split, because there might not be enough pressure to cause the smoke limiter to drop out.

 

[markc]

Dunno...based on only my experience, if there is not enough air being forced in, fuel does not burn properly and hence black smoke. Howver, that was not an engine with electronic managment. As I said - bit difficult without seeing & hearing for real!

M

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[Russell]

yep, I don't know these engines are controlled. I've seen what happens when the smoke limiter doesnt drop out though, no smoke, less power, and a loss in boost.
I guess an electronic management system would be even cleverer, and detect that as there is less boost pressure/air flow then it would supply less diesel.

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[Neil_P]

Could be a turbo pipe. Lack of power can be created by either a pipe before the turbo collapsing as the air is drawn in or a split in the pipe between the turbo and intercooler. There may not be any smoke as there could still be enough air to give full combustion as a naturally aspirated engine.

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[maxtorque]

Thanks to all for their help.
And the answer was:

"the turbo pipe"! It had worked itself off the boost pipe end, so the boosted air was hissing out at about 1.5bar, smack up against the transom.
Huge relief and learned a lot about the workings of a turbo, too.

Many thanks indeed.

All I've got to fix now is my tilt piston seal leak! Oh well couldn't take a joke.......

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