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Diesel engines (again)


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#41 Myjane

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Posted 09 March 2018 - 05:42 AM

Just bin it and treat your self and the boat to a new beta
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#42 Dagwood

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Posted 09 March 2018 - 07:39 AM

Then while either tied to Dock or underway, open throttle while in gear. Does engine reach full RPM or within 10%.

 

Would you expect to get a true test while tied to a dock? Surely the engine would either be overloaded or the cavitation would be so bad the prop would have no grip and therefore the load would be less than normal? 

 

I'm no expert but I would have thought this test would be ideally be done in open water with a clean hull and prop and the boat loaded normally?


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#43 vic008

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Posted 09 March 2018 - 08:45 AM

Priscilla, thanks but couldn't find anything on TM
I'm thinkinf fuel in sump but want to test again.( because of increase on dipstick) Is there a test for this?
Got about 40m to get home so will change oil and filter now and about halfway.
Wheels, reluctant to do your tests if there is fuel in oil.Will do when home. Have never noticed smoke but dirty transom.
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#44 Fish

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Posted 09 March 2018 - 09:13 AM

Lombardini currently have very good pricing on the small boat engines (FOCS series). I did a price check on a 40 Hp and automatically added GST when it already had GST on, cause the price didn't seem right. An offshore distributor closed and the NZ agent bought all of their stock.

 

That said, a Lombardini is a completely different style of engine to the one being discussed. Light (very light) and high revving (as far as diesels go anyway).

 

I'd be interesting in hearing comments from anyone with a Lombardini in a normal displacement type yacht. They are supposed to be very quiet. Understand they are popular in cats and other weight sensitive boats like easily planning race yachts.


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#45 wheels

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Posted 09 March 2018 - 11:19 AM

Would you expect to get a true test while tied to a dock? Surely the engine would either be overloaded or the cavitation would be so bad the prop would have no grip and therefore the load would be less than normal?

 

Yep pretty darn close. The water moves easily. It's not like trying to spin up the tires on the road, where the road doesn't move.

Another thing to check is the Fuel lift pump. If it has a hole in the Diaphragm, it can leak fuel directly into the sump. The engine could be sweet, just fuel leaking. that to me would make more sense for the quantity of fuel being used. I actually can't think of a possible way the injectors could deliver that much fuel on a wee engine like that. Or put it this way. You would notice the smoke out of the exhaust. It should resemble a WW2 Battle Ship putting out a smoke screen.


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#46 Priscilla II

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Posted 09 March 2018 - 12:57 PM

With the engine running how much blow by or venting is there from the rocker cover if the oil filler cap is removed.

Not the listing I had in mind but not a bad option if you have to swap out your old donk.

 

https://www.trademe....da2562eb41098e4QCtdtQ3.jpg


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#47 wheels

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Posted 09 March 2018 - 04:56 PM

You are all getting way to far ahead of yourselves. I doubt very much there is a problem with the engine that it needs replacing or overhaul.


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#48 Priscilla II

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Posted 09 March 2018 - 06:26 PM

It’s just a helpful option if required.
Best have somebody who knows what they are talking about actually look at the engine.
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#49 John B

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Posted 10 March 2018 - 07:02 AM

Check the exhaust mixer/elbow.
They only last 5 or 7 years on many motors.
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#50 wheels

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Posted 10 March 2018 - 07:32 AM

While it is possible the elbow is blocked, that is a secondary fault. This would not cause the overly excessive fuel use.
Diesels are simple beasts. While the intimate workings can be complex, the actual Suck, Bang, Blow part is simple. Fault finding is logical and much of the tell tales of a badly working engine can be seen it's smoke.

So if we apply the above, then we have the following.
Overly excessive Fuel consumption.
Oil level rising in sump, smells of Diesel fuel.
No excessive smoke from the exhaust.
Soot on the Transom.
Engine seems to start OK, run OK.

So using that info, we can assume the engine is in reasonable shape. Diesels have one major issue when they have compression problems. They become very hard to start. Diesel also have a tell tale that help identify many issues. They smoke and the smoke colour will identify the kind of fault. In this case, there has been no obvious report of smoke.
All Diesels, especially the older ones, tend to dirty up the hull around the exhaust. So unless a major change from normal has occurred, we can likely rule that part out.
       That leaves the one an only other place the Fuel can get into the Sump. The Fuel lift pump. When the diaphragm fails, they tend to get a tiny wee pin hole on the rubber. The pump is pushing the fuel to the IP at about 3PSI. That is enough to push fuel pas the rubber and through the otherside of the Pump. the other side has a finger that runs against the Cam and that is all within the internals of the engine. So the Fuel drips straight into the Sump. If the Fuel tank is situated above the Lift pump, then the fuel can continue to drip in even when the engine is not running.
    So that leaves us with the conclusion of a failure in a fairly easy to get at and check item. It would be the first thing worth looking at. After that, the possible faults start becoming rather complex. It is always best to check the easiest most logical faults first.
   Now in saying all that, John B is correct that exhaust elbows are a common failure area. It is often not a silly idea to check that area as part of normal maintenance routine. Say once ever couple of years depending on Engine hrs.


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