Engine blue smoke after long trip...

[Druff1]

I took the family for a long ride, one of the last days out this fall... It was probably 2 hours up river and another 2 hours back. We weren't going wide open the whole way, just cruising on plane... Boat was running perfect as always.

The engine is a 7.4L with a Bravo 3... It has almost 900 hours on it. I always check the engine oil and it is always good. Never uses oil..

So, the boat sat for about a week before i went out again... When i went to start it, quite a bit of blue smoke came out... It went away and i continued out that day... Check the oil and it was still good.. It doesn't seem to do it now, but now that the temps got down in the 50's, there is a lot of black smoke coming out. I'm just figuring it's the choke staying on...

My question is, why did so much blue smoke come out after that long trip?

 

[stonyloam]

Re: Engine blue smoke after long trip...

My 470 (lots of hours) does the same thing, and so does my 2002 Chevy Silverado (160K). I suspect that it may be that valve guides are a little worn, and that on shut down a little hot oil seeps into the cylinders and is burnt off when you start up. I don't worry about it too much as long as it goes away when the engine warms up, and it is not using significant amounts of oil. It doesn't take much oil to make a lot of smoke in a cold engine. Just my opinion.

 

[ralph69]

Re: Engine blue smoke after long trip...

I'm new here,how do I post a new thread?

 

[stonyloam]

Re: Engine blue smoke after long trip...

I'm new here,how do I post a new thread?

On the forum page "Mercruiser, OMC, Volvo & other I/O & Inboard Engines & Outdrives" (one back from here), upper left side, look for the "create new post" button. Hit it and you should be good to go.

 

[Alpheus]

Re: Engine blue smoke after long trip...

why did so much blue smoke come out after that long trip?

Blue smoke = oil burning.

I agree with the first guy who answered your question. If it only smoked for a little bit after start up its because oil made its way into the combustion chamber and it usually indicates worn valve seals. These can easily be replaced if you have an air compressor and a valve spring tool and the seals are pretty cheap.

As for the black smoke that is usually your engine running rich. Check the choke and make sure its opening full when engine is warm...

 

[ralph69]

Re: Engine blue smoke after long trip...

Thanks,I got It!!

 

[boat127]

Re: Engine blue smoke after long trip...

what usually happens is oil sludge builds up in the head and plugs the drain back holes for the oil and prevents oil from seeping back into the oil pan and the oil will seep past the valve seals. thats why it only does it when you start it up. just pull your valve covers and clean out the holes if plugged and replace the gaskets

 

[GLENN M]

Re: Engine blue smoke after long trip...

that never happens,replace with umbella seals as stated using air compressor and spring removal tool.takes an hour.

 

[bruceb58]

Re: Engine blue smoke after long trip...

what usually happens is oil sludge builds up in the head and plugs the drain back holes for the oil and prevents oil from seeping back into the oil pan

if you have that much sludge in your engine, you have bigger problems.