5.7 Mercruiser smokes when first started

[pfd]

I have a 1999 Monterey with a 5.7 mercruiser, carb and thunderbolt V ignition. My problem is that when I first start the boat it starts fine but I get alot of white smoke and a gas smell. I don't pump the throttle, I just turn the key. It runs alittle rough untill I increase throttle to increase Rpms to about 1500 and let it warm up and the smell and the smoke dissipate. Also there is a shean of something on the water. Oil level is stable and it idles fine and runs fine.
Is this a carb adjustment issue?

What can I do to remedy this? It smokes out the neighbors at the slip when I want to go for a ride. Even if it is only for the couple seconds of startup.

 

[pfd]

Re: 5.7 Mercruiser smokes when first started

From what I have gathered the symptoms point to leaky valve seal. That's of course with no compression test yet. What is the typical cost for a valve seal replacement? (if that's the problem) The marina charges $75 per hr. I have read that you can do the seals without removing the head, by using an air compressor to push the valves up. Is that practical? Just trying to gage if it's worth digging into myself or just pay the almighty $$$$$$ and get on with the longly awaited season.

 

[Mkos1980]

Re: 5.7 Mercruiser smokes when first started

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[Mkos1980]

Re: 5.7 Mercruiser smokes when first started

I would even bother with the valve seals. There sa ton of SBC's out there with seal problems. Really doesnt cause a problem. If you have to do them you can get them done in about 3 hours if your handy with an air compressor and a valve spring compressor. The air compressor is the only option with them if the head is on the motor.. (There are others but they are not pratical.)

 

[Fishermark]

Re: 5.7 Mercruiser smokes when first started

I would agree to leave it alone IF if the valve stem seals. But the symptoms point equally well to an over-rich situation at start up. Especially since you mention the gas smell and white smoke. Oil tends to be blueish / grey smoke with a different odor.

 

[mattmck13]

Re: 5.7 Mercruiser smokes when first started

i did all the valvesprins on my 355 byturning motor with a breaker bar on crank pullet to bring the pistons to TDC and then they wont fall in

 

[Polar_Bus]

Re: 5.7 Mercruiser smokes when first started

"black smoke" = rich fuel condition

"blue smoke" = bad intake valve seals. (SBC's are notorious for deteriorated valve seals. I've replaced ton's of em)

"white smoke" = blown head gasket or cracked head between the valves. (water or anti-freeze being burnt)

 

[pfd]

Re: 5.7 Mercruiser smokes when first started

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[pfd]

Re: 5.7 Mercruiser smokes when first started

I fired it up today and again I had smoke which was more grayish and blue today. It was damp and cold and it ran rough till it warmed up and then was fine. A light sheen on the water also.
Not that I want to dump anything in my engine, but what would a quart of stop smoke do?? A friend of mine also suggested to try an oil change and this time use a higher viscosity oil. I currently use 5w30. I'm not really sure what this will do in a marine application and if the oil will still get circulated properly.
I don't want to make a small problem bigger.

More importantly... this is a minor and common issue.

Am I right in saying that?

So at a conveniant time I can change the valve seals and most likely the smoke will be gone and I won't be the skeeter killer on the dock anymore, bottom line.

 

[slasmith1]

Re: 5.7 Mercruiser smokes when first started

I'm sure some one will correct me if I'm wrong but I believe you should be running mercs 25-40 in that motor.

 

[Don S]

Re: 5.7 Mercruiser smokes when first started

You are in Maine. Cool temps, hot exhaust, bit of gray and blue smoke.
Sounds perfectly normal to me. IT has a choke which are set rich by factory specs. The white smoke (steam) is normal in cooler temps when you have 1200? exhaust temps hitting cold water.

 

[HT32BSX115]

Re: 5.7 Mercruiser smokes when first started

but what would a quart of stop smoke do??

It would make more money for the company that manufactures it and the retailer that sells it.

Adding snake oil will not "fix" your engine if there's something wrong with it.

If you're going to change your oil you should follow Mercs recommendations on oil type.



Regards,



Rick