Engine help (divemaster1)

[petem]

Why would the “ valve “ spontaneously close ? Anybody.
Jez,s first post inference was the black smoke came at D and also he feels it’s wont plane transfer the P .
Suppose a long time at D the rings never heat up and seal as much as P .So minor combustion products get past and maybe via the crank case management of the excess fumes , 8hit gets redirected into the air supply pre turbo and eventually “ gums “ up the vanes of the turbo blades ? Is that what the “ stuck turbo” contingent “ are suggesting??

Nah .Its an injector issue that’s where my money is .

See - https://www.thehulltruth.com/boating-forum/589627-detroit-6v92-425hp-black-smoke.html

 

[petem]

J.,

Should be fairly easy to remove the air filter and with the engine shut, try with a finger to spin the turbo blades, no?
Is it the first real run of the boat since last season?
If not, I very much doubt it's the turbo...

V

It's the boat's first proper run out for the season I believe. No time for sea trial last week. New alternator has just been fitted, not beyond the realms of possibility that something has been knocked.

 

[Assassin]

6v92 being a two Stoke has an emergency shit down airflap just in case of a run away engine . You should see it in front of turbos. There is a lever on the side, if it has been activated you twist lever until it latches open again.

Shitting into any engines airflow will restrict airflow, use the toilet instead.

 

[Assassin]

Both good points. They were last she was run but I’ll check.

Roger the injector PF, but no symptoms below the turbo point. Not sure how easily a Detroit injector can be repaired - still hoping Alf might appear

Very easily and cheaply and I would suggest testing them in the engine first, any specialist can check the break pressures and this would identify an injector problem as the break pressures would be either lower or higher than the manufacturers recommendation, and an average 5 year old can rebuild them and shim them to the correct break pressures.

 

[Kawasaki]

Shitting into any engines airflow will restrict airflow, use the toilet instead.

:encouragement:

 

[Whitelighter]

Update on this:

Pulled filter and housing. Nice and clean/clear.
Stuck fingers in turbo, couldn’t move it.
Put socket on turbo and freed it
Ran boat, no smoke and 20 knots.

Thanks for all replies and support.

As an aside, took pics to post as can’t see shut off thingy anywhere

 

[kashurst]

Great news, have a lovely holiday

 

[GSL]

Very pleased for you Jez

 

[NorthUp]

Good news

 

[stelican]

Update on this:

Pulled filter and housing. Nice and clean/clear.
Stuck fingers in turbo, couldn’t move it.
Put socket on turbo and freed it
Ran boat, no smoke and 20 knots.

Thanks for all replies and support.

As an aside, took pics to post as can’t see shut off thingy anywhere

Thought so! Glad easy fix. Mine would stick if not used for four weeks and being sternd.rive it would leave black streak behind boat

 

[Divemaster1]

Sorry Jez, on boat with no electronic devices ... ...

Simple engines = simple solution ... big black smoke means all injectors over-fueling and they very seldom fail all at the same time (each injector is its own fuel pump) .... a single stuck injector will also give fuel sheen on water at idle ... so was most likely to be lack of air considering the volume of smoke...

With the Blower air shield closed, you may still be able of running(if tripped) really billowing black smoke and you most definitely would hear it on the engine note and performance the second the shield was activated , but you would not manage to start or really throttle up the engine under load from cold with the shield triggered... so most likely problem would have been the turbocharger (if it was the blower (compressor), you would not have had over pressure in the air chambers and again no joy in starting the engines).

Worth taking off the valve rocker cover, get the injector size from the side of the injector (near the fuel rack clevis)

Then order one (about £180) to have as a spare onboard in case you actually do have an injector failure...

 

[Divemaster1]

Oh, and just for your familiarisation, on your 6V92's the air shutdown mechanism will sit at the top front of your blower and will be solenoid operated, so most likely to be a push button at your helm position and once activated, it will be a manual reset, .....a simple spring loaded mechanism where the valve simply is manually lifted and locked into place ... see highlighted area at the top of picture...

 

[Elessar]

Oh, and just for your familiarisation, on your 6V92's the air shutdown mechanism will sit at the top front of your blower and will be solenoid operated, so most likely to be a push button at your helm position and once activated, it will be a manual reset, which is a simple spring loaded mechanism where the valve simply is manually lifted and locked into place ... see highlighted are at the top of picture...

That would be a very annoying thing not to know.

Great posts as always Alf!

 

[Divemaster1]

Jez,

As the nights are getting longer and boat use may drop a bit, people may start to look at putting their boats into "hibernation" ... and there are a couple of things you can do with a DD 2 stroke which may help prevent things like you have experienced here ... and other wear & tear issues...

When I put Navigator into hibernation, I deliberately shut the air intake... The reason for this is quite simple the fact that on a 2 stroke with scavenging ports, most likely the exhaust valves on one of the cylinders will be left open ... and at that stage, the scavenging port will also be exposed (over pressure in air chamber forces exhaust gases out). this condition leads to an air-circulation path from the air intake to the exhaust system (or reverse).... Air circulation will then potentially bring in humidity etc., which may cause surface corrosion on sensitive parts exposed to the air circulation (piston rings, valve seats, turbo vanes etc. ). Simply closing the air intake near the blower, will stop that circulation reducing risk etc.... but it is good to leave a wee note on the keys saying "Air Shutoff" as you will not get the engines started without air

 

[Whitelighter]

Brilliant Thanks Alf