SR2 smoking

[claudia]

Could anyone shed any light on my problem, my SR2 seems to rev to max no problem when off load but when in gear it seems to struggle and give off alot of black smoke and does not seem to have much power at all. The prop shaft runs very free with no binding, I have changed all fuel filters and fuel line it has a new fuel pump and air filter, any thoughts anyone cheers, Ian.

[Timleech]

Could anyone shed any light on my problem, my SR2 seems to rev to max no problem when off load but when in gear it seems to struggle and give off alot of black smoke and does not seem to have much power at all. The prop shaft runs very free with no binding, I have changed all fuel filters and fuel line it has a new fuel pump and air filter, any thoughts anyone cheers, Ian.

 

Get the injectors checked. There could be other causes, but mucky injectors is one they are prone to suffering from.

 

Tim

[Burgiesburnin]

Could anyone shed any light on my problem, my SR2 seems to rev to max no problem when off load but when in gear it seems to struggle and give off alot of black smoke and does not seem to have much power at all. The prop shaft runs very free with no binding, I have changed all fuel filters and fuel line it has a new fuel pump and air filter, any thoughts anyone cheers, Ian.

 

This seems fuel related to me. Did you change the fuel filters, line and pump as a remedy to the problem or was it performing well after replacing these items and has now deteriorated?

[claudia]

All filters are new this problem has been there all the time I have had it. I think Bizard has some reconed injectors I think that must be where I start on this one.

[Albion]

All filters are new this problem has been there all the time I have had it. I think Bizard has some reconed injectors I think that must be where I start on this one.

 

Do you mean that the problem has been there all the time that you've owned the boat (and/or the engine in the boat)?

If that is the case it could be over-propped perhaps.

Roger

[Timleech]

Do you mean that the problem has been there all the time that you've owned the boat (and/or the engine in the boat)?

If that is the case it could be over-propped perhaps.

Roger

 

In theory, if the fuel system is all in good order and pumps properly set up, the engine should fail to reach working speed but without serious smoke if the prop is too big. I realise that life isn't always perfectly as it should be, though

 

Tim

[nigel carton]

Double check you have nothing wrapped around your prop.

[Albion]

In theory, if the fuel system is all in good order and pumps properly set up, the engine should fail to reach working speed but without serious smoke if the prop is too big. I realise that life isn't always perfectly as it should be, though

 

Tim

 

I can sort of get your argument if the revs rise to a set point allowed by the size of the prop and the (perfect) governor then controls the fuel to those revs accordingly but why wouldn't the governor be trying to get the engine to max set(allowable)(taken as full throttle in this thread) revs and open the rack accordingly thereby injecting more fuel and black smoking at the prop strangled revs?

Roger

[Timleech]

I can sort of get your argument if the revs rise to a set point allowed by the size of the prop and the (perfect) governor then controls the fuel to those revs accordingly but why wouldn't the governor be trying to get the engine to max set(allowable)(taken as full throttle in this thread) revs and open the rack accordingly thereby injecting more fuel and black smoking at the prop strangled revs?

Roger

 

Because the amount of fuel injected per stroke is or should be limited to the amount which can be properly burned (ie without smoke).

 

Tim

[Albion]

Because the amount of fuel injected per stroke is or should be limited to the amount which can be properly burned (ie without smoke).

 

Tim

 

But you're still requesting a further increase in revs and the only way you get a diesel to accelerate is to inject more fuel (as they run in excess of freely available air) and so in a non-steady-state (ie acceleration under load) you will always be injecting some excess fuel or it won't accelerate further. Steady state conditions I agree with you completely, but I can't see how you're going to get the engine to accelerate without running some excess of fuel. Even hi-tech common rail engines in cars smoke more during acceleration and they have very finely controlled mixture delivery.

Roger

Edited December 11, 2011 by Albion

[claudia]

I have read these last few posts several times and the conclusion I have come to is that I am quite thick are we trying to establish that an engine will not accelerate if the load on it is to great. The prop size was worked out by Crowthers and confirmed by a couple of guys on here I was sure that bit was right.

[Tony Brooks]

I have read these last few posts several times and the conclusion I have come to is that I am quite thick are we trying to establish that an engine will not accelerate if the load on it is to great. The prop size was worked out by Crowthers and confirmed by a couple of guys on here I was sure that bit was right.

 

It will only be right if you gave them the correct reduction ratio. If there is in fact no reduction box and you told them There was (by specifying something other than a 1:1 ratio) then the prop will be too large. However unless the prop is stupidly oversize I would expect the engine to rev to a certain extent before exhibiting these symptoms.

 

Make sure there is nothing preventing the free flow of air into the engine AND the free exit of exhaust gasses.

 

It may also be worth getting someone who knows how to do it and has the equipment to check the timing of the individual injector pumps (there should be shims under them) and while inside the housing to make sure the rack is correctly adjusted for both pumps. After that I go with Tim and he could well be right all along. However this could be something odd like a rag stuffed into the inlet of exhaust manifold.

[Albion]

I have read these last few posts several times and the conclusion I have come to is that I am quite thick are we trying to establish that an engine will not accelerate if the load on it is to great. The prop size was worked out by Crowthers and confirmed by a couple of guys on here I was sure that bit was right.

 

If the prop has been sized correctly, as it seems from your posting that that is the case, then ignore what I said. It seemed from the phrasing of one of your posts that it might not have been the case but, obviously, not so.

 

Yes, any engine won't be able to accelerate if the load that is applied at that moment is greater than the power that it can develop at those revs. Taken to extreme, and with an ever increasing load, you could stall the engine. Imagine someone who stalls their car at the traffic lights, they have exceeded the load that the engine could develop at the revs they gave it, usually by clumsy throttle/clutch co-ordination. Same thing with any engine.

Roger

[Timleech]

But you're still requesting a further increase in revs and the only way you get a diesel to accelerate is to inject more fuel (as they run in excess of freely available air) and so in a non-steady-state (ie acceleration under load) you will always be injecting some excess fuel or it won't accelerate further. Steady state conditions I agree with you completely, but I can't see how you're going to get the engine to accelerate without running some excess of fuel. Even hi-tech common rail engines in cars smoke more during acceleration and they have very finely controlled mixture delivery.

Roger

 

Quite simple, with a marine propulsion engine, with properly matched propeller, it's never under normal conditions required to deliver maximum torque (or power for a given rpm) except at full power/speed.

 

Tim

[bizzard]

Ok we take for granted that the props the correct match for the SR2 engine with an 2.1 reduction box,as determined by you Ian by following my checking instructions a while ago,and double checked i think,''chalk marks ect''.

Providing there's nothing caught up on the prop we're back to the engine. Are you sure its running on both cylinders.A quick check can be done by.--start engine and out of gear,operate each decompressor lever in turn and provided these levers are adjusted properly will indicate if a cylinder is not working by as follows.---By lifting each leaver in turn the one that stops the engine is the only cylinder working. If one of levers makes no difference at all that cylinder is doing nothing. If either lever makes the engine falter more than the other then that cylinder is doing more work than the other so there would be something wrong with the cylinder that the lever affected less.

Hopefully if you find a big discrepancy doing this test its only an injector fault usually the nozzle ghoood up with soot ect. If so a good way to try and clean the injectors is to remove your small Crosland type fuel filter bowl,tip about half the diesel fuel out and top it up with neat ''Diesel engine fuel system cleaner''Whack it back on quickly,bleed it a little by its top vent by working the fuel lift pump lever,tighten vent screw and start up on full throttle.If the engine was running on one cylinder and it is a dirty injector fault and the treatment works you will hear the faulty cylinder begin to chime in and engine will be much smoother and power will be restored. Of course there are other things that cause this power loss. But try this first as as Tim said sooted up injectors on these engines is quite common.

[claudia]

I will do your testing in the week Bizzard and report back if there is a injector down would I not be best just getting some recond injectors and fitting them to bring it back to how it should be.

[bizzard]

I will do your testing in the week Bizzard and report back if there is a injector down would I not be best just getting some recond injectors and fitting them to bring it back to how it should be.

It might not be them.Do the test with the levers first and the filter bowl half full of diesel cleaner thing and report back. I still have those two injectors yes.

Do you think it sounds like it could be running on only one cylinder ?

[Tony Brooks]

Could anyone shed any light on my problem, my SR2 seems to rev to max no problem when off load but when in gear it seems to struggle and give off alot of black smoke and does not seem to have much power at all. The prop shaft runs very free with no binding, I have changed all fuel filters and fuel line it has a new fuel pump and air filter, any thoughts anyone cheers, Ian.

 

I have just realised that the prop runs free thing could be a clue. If the gearbox is a LH150 hydraulic box then most boaters would complain that the shaft was seized up in neutral with the engine not running so an LH150 with a free turning shaft could indicate a gearbox problem of some sort.

[claudia]

Thanks for the reply Tony but I really don't think I have a gearbox issue apart from I have a very odd Italian box that does have a 2-1 ratio. My thoughts on the box were more to do with the shaft being stiff causing drag but this is not the case.

 

Hi Bizzard, if it is on 1 then it has been that way since I got it. the engine starts very well and ticks over nicely, not sure what impact a dead cylinder would have on running other than the obvious lack of power which I believe are your thoughts.

[bizzard]

I have just realised that the prop runs free thing could be a clue. If the gearbox is a LH150 hydraulic box then most boaters would complain that the shaft was seized up in neutral with the engine not running so an LH150 with a free turning shaft could indicate a gearbox problem of some sort.

Its not an LH150 Tony its a strange we Ducatte box we think,we've been in to it before with Ian.

[Albion]

Its not an LH150 Tony its a strange we Ducatte box we think,we've been in to it before with Ian.

 

Was this the strange Italian box that we were trying to decide where and how to check the oil level? A bolt head in one corner was the dipstick IIRC.

Roger

[bizzard]

Was this the strange Italian box that we were trying to decide where and how to check the oil level? A bolt head in one corner was the dipstick IIRC.

Roger

Thats the one.

[claudia]

In deed that was the one and I felt a dipstick for not working it out that that would be the dip stick so obvious now.

[bizzard]

Thanks for the reply Tony but I really don't think I have a gearbox issue apart from I have a very odd Italian box that does have a 2-1 ratio. My thoughts on the box were more to do with the shaft being stiff causing drag but this is not the case.

 

Hi Bizzard, if it is on 1 then it has been that way since I got it. the engine starts very well and ticks over nicely, not sure what impact a dead cylinder would have on running other than the obvious lack of power which I believe are your thoughts.

Those engines do sound quite nice on one cylinder but their power output is cut from about 13hp to around 5hp to include all the frictional losses of the dead cylinder.

[Albion]

In deed that was the one and I felt a dipstick for not working it out that that would be the dip stick so obvious now.

 

I'm sure we've all made mistakes equally as painful to our ego, so don't worry about it. These things happen.

Roger

 

Those engines do sound quite nice on one cylinder but their power output is cut from about 13hp to around 5hp to include all the frictional losses of the dead cylinder.

 

Surely if you lost one cylinder completely on a two cylinder engine the tickover couldn't be described as sweet? I would have thought it would have been glaringly obvious just by the sound? I've known one cylinder on a V12 go down and be hard to detect but one on a two should be spottable I would have thought. You are right though that, on such a low power output engine, any loss of cylinder efficiency is going to have a significant effect. Has the decompressor test been done?

Roger