Sudden rattle from engine for a few seconds

[Tamar]

Out on my friends fishing boat today. we were steaming along for around an hour when suddenly the engine started rattling and some blue smoke came out of the exhaust then it cleared and ran perfect all afternoon.
I said it's probably dirty fuel, but anything else it could be?

 

[Montemar]

Blue smoke indicates burnt oil and black smoke indicates burnt fuel.
Check the oil level.

 

[QBhoy]

Blue smoke indicates burnt oil and black smoke indicates burnt fuel.
Check the oil level.

I’d say black smoke indicates fuel not getting burnt properly. But yeah…blue smoke isn’t good. Burning oil for sure.

 

[DavidJ]

I don’t know what engine it is so my theory is for a push rod engine
Valve gets stuck
rattle rattle of the push rod, unburnt fuel (lucky that the push rod didn’t come out completely and lucky the piston didn’t hit the valve…..or maybe it did!!
Valve gets unstuck….all is well until next time.

 

[Tamar]

I don’t know what engine it is so my theory is for a push rod engine
Valve gets stuck
rattle rattle of the push rod, unburnt fuel (lucky that the push rod didn’t come out completely and lucky the piston didn’t hit the valve…..or maybe it did!!
Valve gets unstuck….all is well until next time.

It's a small Perkins around 30 hp. I was thinking dirty fuel. The engine ran sweetly all day after this little hic up

 

[Portofino]

I don’t know what engine it is so my theory is for a push rod engine
Valve gets stuck
rattle rattle of the push rod, unburnt fuel (lucky that the push rod didn’t come out completely and lucky the piston didn’t hit the valve…..or maybe it did!!
Valve gets unstuck….all is well until next time.

Push Rods bend and the rocker fractures with this ^^^ .
It does not self fix .

An open valve in a interference engine ( one whereby the valves and pistons potentially occupy the same space ) causes irreparable damage as they meet .
In a not inference engine which older simpler less powerful motors are likely to be an open valve stuck causes a banging noise as explosion escapes back .Black smoke as said is over fuel ing unburnt fuel .

Depends on the colour it’s reported blue = oil if it was blue .Then back to normal .

Could be a cracked piston ring which moved or stuck a bit then self sealed ? Or a worn valve guide like wise .

Interesting to know the oil change Fq and quality ? Also the rpm and prop hygiene side ?
Wether it repeats more frequently next few trips out ?

If it was a bit of 8hit impeding injector then loosing a cylinder momentarily will cause in a small banger a huge shudder + vibration = the reported rattle as the motor shook about clanging its pipage etc .May be the smoke was unburnt fuel black but appeared blue ish ?

Old tank , old fuel , not so good filtration .Older basic engines can cope .It’s newer CR / ECU electrotwackerey motors that throw codes and limp modes .= the injectors on CR s are so temperamental it a show stopper 8hit or water in fuel and leads to a destroyed tips= hosing = hole in piston .

This good” old school “ Perkins I assume can survive a injector incident with 8hit fuel .

Advise your mate to put some fuel bug treatment in the water dissolutions version and check replace the O ring on the tank filler .

 

[Tamar]

Push Rods bend and the rocker fractures with this ^^^ .
It does not self fix .

An open valve in a interference engine ( one whereby the valves and pistons potentially occupy the same space ) causes irreparable damage as they meet .
In a not inference engine which older simpler less powerful motors are likely to be an open valve stuck causes a banging noise as explosion escapes back .Black smoke as said is over fuel ing unburnt fuel .

Depends on the colour it’s reported blue = oil if it was blue .Then back to normal .

Could be a cracked piston ring which moved or stuck a bit then self sealed ? Or a worn valve guide like wise .

Interesting to know the oil change Fq and quality ? Also the rpm and prop hygiene side ?
Wether it repeats more frequently next few trips out ?

If it was a bit of 8hit impeding injector then loosing a cylinder momentarily will cause in a small banger a huge shudder + vibration = the reported rattle as the motor shook about clanging its pipage etc .May be the smoke was unburnt fuel black but appeared blue ish ?

Old tank , old fuel , not so good filtration .Older basic engines can cope .It’s newer CR / ECU electrotwackerey motors that throw codes and limp modes .= the injectors on CR s are so temperamental it a show stopper 8hit or water in fuel and leads to a destroyed tips= hosing = hole in piston .

This good” old school “ Perkins I assume can survive a injector incident with 8hit fuel .

Advise your mate to put some fuel bug treatment in the water dissolutions version and check replace the O ring on the tank filler .

The engine is 1997 so old school thank goodness. I think the smoke was blue or grey but it was only a little smoke, this engine never smoked all through the guys ownership of 10 years. Good oil changing regime.
I am going down to the boat today to help him change the oil and fuel filters. Perhaps it was a blocked injector, we will also check the tappets. Start on the simple things first is my advice, before going for open heart surgery if it persists.

 

[Bigplumbs]

It's a small Perkins around 30 hp. I was thinking dirty fuel. The engine ran sweetly all day after this little hic up

Now you have posted this people will jump in and scare you to death and suggest a complete engine rebuild Or similar. Perhaps it was just a pop and a fart…….These things happen.

 

[Tamar]

Now you have posted this people will jump in and scare you to death and suggest a complete engine rebuild Or similar. Perhaps it was just a pop and a fart…….These things happen.

Yes he's already looking at beta marine brochures ?

 

[Tamar]

We just did a 9 hour trip after changing fuel filters, oil, and dosing the fuel with poison, the engine ran sweetly and never missed a beat. I'm guessing fuel contamination was the cause of the initial problem, the Secondary filter had some black gunge deposits.
Thanks for all advice.

 

[Bigplumbs]

We just did a 9 hour trip after changing fuel filters, oil, and dosing the fuel with poison, the engine ran sweetly and never missed a beat. I'm guessing fuel contamination was the cause of the initial problem, the Secondary filter had some black gunge deposits.
Thanks for all advice.

So seemingly a cheap simple fix.

My wife ’blew up’ her oven the other day. It was 12 years old so I think she was looking forward to a new one. Bought a new heating element from eBay for £16 replaced it in 15 mins……. I think she was pleased