Engine sounds odd!

[Gabby_Boating]

Hey all - Could I ask for some advice? We've recently moved on board a new boat and are slowly learning her 'charms' Things like having to replace the gearbox two weeks after buying her! Ah boats!

 

We have a BMC 1.8 engine. After a day of cruising the noise from it has gone from being the usual diesel rumble to that combined with a 'put put put' noise... Also not sure if it's a coincidence but the exhaust seemed a lot more smokey than normal with white smoke coming out.

 

Anyone have any suspicions with what it could be? The heat wrap around the exhaust has started to come off around the join from the engine to the exhaust. Could this be why it's louder or something more significant!?

 

Uploaded the sound here: 

 

 

Thank you!!

Edited December 8, 2021 by Gabby&Jack

[Tracy D'arth]

Hold a rag firmly over the exhaust outlet whilst watching and listening to the engine. You will quickly discover if the exhaust is split and leaking.

 

If it is stop, using the boat, Carbon Monoxide fumes inside will kill you.

[Athy]

I listened to the engine noise cip (which arrived by e-mail !) It sounds healthy and regular to me, but then I have never had a BMC engine.

[Tony Brooks]

I don't have a Google account so can't listen to it. Maybe post a video here. From your words it sounds as if you might have a misfire (note might) and if s it needs sorting. There are several things that could cause a misfire form simple and cheap to fix to "Ow much!"

[David Mack]

1 hour ago, Gabby&Jack said:

 

Uploaded the sound here: https://drive.google.com/drive/folders/19ZbfU4gGXc1Oj1YrLDhOlKKtDvdhAbrZ?usp=sharing

 

Thank you!!

 

Gawd, I have to wait for an email!!  Upload to YouTube and post a link here so we can all have a listen.

[Gabby_Boating]

Thank you everyone! Sorry the Google link is a faff.....uploaded to YouTube here (I hope!) 

 

https://youtube.com/shorts/f4FuEwiST8I?feature=share

[Alan de Enfield]

22 minutes ago, David Mack said:

YouTube and post a link here so we can all have a listen.

 

Not ALL by any stretch of the imagination

[MtB]

2 hours ago, Tracy D'arth said:

Hold a rag firmly over the exhaust outlet whilst watching and listening to the engine. You will quickly discover if the exhaust is split and leaking.

 

If it is stop, using the boat, Carbon Monoxide fumes inside will kill you.

 

 

Point of Order M'lud...

 

Carbon monoxide is a serious danger with petrol engines, but not diesel AIUI.

 

CO is a product of incomplete combustion caused by lack of oxygen. A diesel runs with a full cylinder of air whatever the speed setting so there is never a shortage of oxygen (except possibly for brief periods when over-fueled by the governor) and consequently, only small traces of CO in the exhaust. 

 

A petrol engine with a carburettor on the other hand, regulates speed by throttling back the air intake so especially at tickover, the exhaust is laden with CO. 

 

 

[Tracy D'arth]

19 minutes ago, MtB said:

 

 

Point of Order M'lud...

 

Carbon monoxide is a serious danger with petrol engines, but not diesel AIUI.

 

CO is a product of incomplete combustion caused by lack of oxygen. A diesel runs with a full cylinder of air whatever the speed setting so there is never a shortage of oxygen (except possibly for brief periods when over-fueled by the governor) and consequently, only small traces of CO in the exhaust. 

 

A petrol engine with a carburettor on the other hand, regulates speed by throttling back the air intake so especially at tickover, the exhaust is laden with CO. 

 

 

I must edit it then.

 

If it is carry on using the boat with impunity, CO will not kill you.

 

Considering that it is massively overfueled and producing white smoke.

 

Is that better?

[Tony Brooks]

The sound file is very quiet, I would need to see and hear the engine to even start to give an opinion. There did seem to be a bit of an odd tick to the noise.

[MtB]

30 minutes ago, Tracy D'arth said:

I must edit it then.

 

If it is carry on using the boat with impunity, CO will not kill you.

 

Considering that it is massively overfueled and producing white smoke.

 

Is that better?

 

White smoke = unburned fuel, yes?

[Stroudwater1]

The need for a new gearbox 2 weeks after purchase is unfortunate- could this be related to the gearbox change, something knocked/ seal loosened perhaps? Was it RCR that changed it? I cant hear much with the sound turned right up TBH . 

[zenataomm]

What does "AIUI" mean in English as I understand it?

[Tony Brooks]

17 minutes ago, Stroudwater1 said:

The need for a new gearbox 2 weeks after purchase is unfortunate- could this be related to the gearbox change, something knocked/ seal loosened perhaps? Was it RCR that changed it? I cant hear much with the sound turned right up TBH . 

 

Now you say that I wonder if the rear mounts were loosened to raise the box above the shaft coupling and they have not been tightened  or the shaft is misaligned.

 

Gabby & Jack - when it is making the noise put your boot against one side f the engine and push it hard sideways. Best use the header tank/manifold side. If the noise alters or goes away the suspect mounts. This is  along shot without much info.

[Gabby_Boating]

Thank you all, this is really helpful. We're going to try and take a better recording of the noise as it did sound a little bit worse than it did in the video. We'll try the rag exhaust tip, and push the engine sideways to see if that makes a difference to the sound...our engineer that fixed the gearbox said our mounts needed sorting so it could be that! Thank you all as always!! 

[Tony Brooks]

2 minutes ago, Gabby&Jack said:

Thank you all, this is really helpful. We're going to try and take a better recording of the noise as it did sound a little bit worse than it did in the video. We'll try the rag exhaust tip, and push the engine sideways to see if that makes a difference to the sound...our engineer that fixed the gearbox said our mounts needed sorting so it could be that! Thank you all as always!! 

 

It looks as if you recorded the sound on a phone, won't it also take video with sound. We really need to watch the engine to see what it does as the  sound occurs.

[Gabby_Boating]

Sure, thanks Tony we'll take a video 😊

[Tracy D'arth]

So if its not right, get RCR clowns back in?  Just a thought.

[Gabby_Boating]

Okay - slightly hoping this isn't the issue as this might be v embarrassing... Could the sound be the cause of no fuel? On our old boat we had a huge fuel tank and never ran out before filling up... 

 

Tried to start the boat today - but when I turn the key back the engine cuts out. So this isn't fully a video of the knocking sound, but possibly the cause of the problem...

 

Video here: 

 

[Alan de Enfield]

You would certainly get the same sort of noise and lack of running if you are out of fuel.

[Tony Brooks]

Assuming you have enough fuel (over 6" in the tank) then that looks and sounds like some kind of misfire. I am not surprised it won't idle as I suspect it is only running on three cylinders.

 

I think I can hear a chuff from the inlet or exhaust so first check the valve clearances in case one has tightened up or something has bent so the valve wont open. It is perfectly safe to spin the engine with the rocker cover off so you can see what is going on, but for the sake of your clothing don't rev it or you will be splattered in oil.

 

I can't see any fuel leaks so if the valve clearances are OK I fear you may need a compression test to see if the head gasket has blown or, more likely, a valve has burned out.

 

[Gabby_Boating]

Great thank you! We're now sadly off the boat until Monday but will check out the valves etc straight away when we're back. Thank you!! 

[Tony Brooks]

If you have done them on a car  or bike use the process that you are familiar with, be it piston pairs, rule of nine or valve fully open and one more complete crank turn.

[Gabby_Boating]

Super helpful thanks Tony