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blue smoke at startup and oil consumption

N

nhuyck

New member
I have a 1998 Merc 350 with a 2 bbl carb with a Bravo III on the back. I bought the boat last year and noticed this year that my oil consumtion is up quite a bit and the motor puts out a little bluish/black smoke upon startup (for about 20-40 seconds). I also have to bring the RPM's up to 800-1000 for a minute or so until it will run clean after I start it. I have fogged it last fall according to the engine manual and stored it indoors with the engine compartment cracked for ventalation. Other than that, after warm-up, the motor runs beautifully. Oil consumption is about a quart every 15 hours or so.



Thanks
 
the opinions on this subject will vary greatly. research research and research you will find prices from $500.00-$3500.00. myself I would purchase a reman 1998 350 long block and use my parts ( carb, intake manifold, riser's, ex manifolds etc) that is the easiest way to get back in the water and running. I'm sure you will get a lot of opinions on this thread.
 
I would perform a compression and leakdown test to see if it is worn rings. It may just get by w/installing valve guide seals.
 
2X on doing the diagnostic testing BEFORE you tear it apart.

I'd suspect it has less than a 1000 hours and hasn't been properly maintained...the top end will be the first thing to go...that means sending the heads to the machine shop.
 
dude ! 1 qt. every 15 hrs ...do a compression test.. do a valve job .. then when the smoke clears do a piston ring job....or buy a case of oil every season or run like that and wait for the KNOCK.:eek:
 
As guyjg and Makomark wisely state, do intelligent diagnostics before spending your hard earned cash needlessly. Most likely, all you need is Valve Stem Umbrella Seals which are not too hard a job for most shade tree mechanics. Let us know how things go. Al W.
 
Remove the valve covers and be sure the oil return passages are not blocked....if that is not the problem, take mikeys advice...life is short...the boating season is short...add a can of STP( oil thickener) and enjoy as many seasons as possible!
 
Here are the findings from a leak-down test: I had the compresser set to 80 psi and I set the regulator on the leak-down gauge to 70 psi

Cyl #1 down 2psi
Cyl#8 down 4psi
Cyl#4 down 9psi
Cyl#3 down 5psi
Cyl#6 down 22psi (air is coming out of the exhast port on the lower unit)
Cyl#5 Down 2psi
Cyl#7 down 4psi
Cyl#2 down 2psi

All of the air that is leaking from #6 is coming out of the exhaust outlet on the lower unit. I am gatherng that I have a problem with an exhaust valve and/or since it is a fresh water cooled engine, possibly the head gasket. I am still burning large amounts of oil, and the plug from number 3 and number 5 have a white calcium crust on them.
 

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Me i would polish the valve and seats myself on the bench or send it out to be done. Compression numbers bad ?

I agree almost 100% with Guy's reply's this time is no exception " It may just get by w/installing valve guide seals."
 
Have you been using any octane boosters or enhancers? They will foul plugs quickly. Run a can of Seafoam thru it to get rid of the crap buildup on the valves.
 
Typically blue smoke at oil startup is a sign of engine oil leaking into the combustion chamber after shut off due to bad valve guide seals. Once the oil burns off, it will quit smoking until you shut engine off again and the oil sets on the guide seal and leaks down. They have probably gotten hot/brittle and need to be replaced. They aren't too hard to do with a valve spring compressor while the cylinder head is still on the engine. However, if you're having these problems, worn piston rings are a high possibility at this stage as well.
 
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