5.0 Mercruiser Smoking

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May 15, 2010
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I have a 1999 searay 215 express cruiser with 220 hours on it. It has a 5.0 mercruiser and a gen 2 alpha one outdrive with the same amount of hours on it.. If i am idling thru a cove the is alot of smoke coming of of the exhaust.. Today i rebuilt the carb and it runs alot better but there is still alot of smoke..can someone please help? It isnt burning any oil at all and it has had regular maintenece performed on it..Would a built 350 bolt right up to the unit i got and if so do you think a crate motor will give me alot more mph..i am running about 45-48 depending on how many people are in the boat..please let me know something.. thanks and i am glad that u all are here
 

ktbarrentine

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Re: 5.0 Mercruiser Smoking

I'm not unhappy with a 5.0 that will pull 45-48 mph (is that true GPS mph?).... What is your WOT RPM? I'm guessiing 4600-4800 rpm?

Have you checked/adjusted your choke to spec? just a thought and easy to do.
 

r.j.dawg

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Re: 5.0 Mercruiser Smoking

Sorry I don't have an answer for you, other than it may be piston rings. My slip neighbor has twin 1999 5.0's and they smoke like he is fogging for mosquitos when he starts up. Im interested to hear the experts. I am assuming white smoke??
 
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Re: 5.0 Mercruiser Smoking

yes white smoke and i adjusted the air/fuel mixture right today when i rebuilt the carb..i know my way around engines very well and i did it right..do u think adjusting the choke will have an effect? i thought about the rings also but it does have low hours on it..is that normal for it to need rings this early? please let me know
 

Scott Danforth

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Re: 5.0 Mercruiser Smoking

white smoke is generally steam. check your manifolds and risers.

on the 99's that smoke, have your neighbor check the valve seals. its not a 5.0 thing, its an SBC thing

yes, a 5.7 and 5.0 will bolt in place of each other. externally they are identical (assuming you have the same generation). its only internally that the bore is different. 4" vs 3.73"
 

04fxdwgi

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Re: 5.0 Mercruiser Smoking

Yup... Bluish smoke is oil, white it water steam / antifreeze and black is fuel / rich.
 
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Re: 5.0 Mercruiser Smoking

Yup... Bluish smoke is oil, white it water steam / antifreeze and black is fuel / rich.
It is. Of blue or black. It is more white. What would make it do that. Some of U are saying steam. What is that from. What can correct the problem. Also someone said adjust the choke which way should I turn the adjustment left or right. Why would the choke make it smOke
 

ktbarrentine

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Re: 5.0 Mercruiser Smoking

A closed choke plate will make you run rich, which would tend to be blacker smoke... Typically the case when warming up a cold engine, until the choke opens. easy to check. With engine cold, give one full pump on throttle to 'set" the choke... should be nearly completely closed. After engine starts, the plate slowly opens fully. If you have electric choke and it is not working, it may remain closed, or in my case, it was just plain stuck! Service manual gives good instructions to set the choke (with engine cold). I basically just loosen the three screws, and turn the housing until the choke plate closes on a 1/8" drill bit (plate -to-airhorn). All that being said, I dont think this is your issue, but you can give it a look-see.
 

Bondo

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Re: 5.0 Mercruiser Smoking

I have a 1999 searay 215 express cruiser with 220 hours on it. It has a 5.0 mercruiser and a gen 2 alpha one outdrive with the same amount of hours on it.. If i am idling thru a cove the is alot of smoke coming of of the exhaust.. Today i rebuilt the carb and it runs alot better but there is still alot of smoke..can someone please help? It isnt burning any oil at all and it has had regular maintenece performed on it..Would a built 350 bolt right up to the unit i got and if so do you think a crate motor will give me alot more mph..i am running about 45-48 depending on how many people are in the boat..please let me know something.. thanks and i am glad that u all are here

Ayuh,.... Pull, 'n Inspect the Spark Plugs,....

They'll tell ya what's goin' on, just by their color, 'n condition....
 

BRG25

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Re: 5.0 Mercruiser Smoking

I would bet your exhaust manifolds are original. They rust internally and can leak water into the engine. They should be replaced every 10 years. What do your spark plugs look like?
 

Scott Danforth

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Re: 5.0 Mercruiser Smoking

It is. Of blue or black. It is more white. What would make it do that. Some of U are saying steam. What is that from. What can correct the problem. Also someone said adjust the choke which way should I turn the adjustment left or right. Why would the choke make it smOke

yes the choke setting wrong would make it smoke

however if its more white, pull your risers and inspect the risers and manifolds. I bet you find the problem.
 
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Re: 5.0 Mercruiser Smoking

Ayuh,.... Pull, 'n Inspect the Spark Plugs,....

They'll tell ya what's goin' on, just by their color, 'n condition....

when i rebuilt the carb i replaced the plugs also..this is the second time that i had done it within 25 hours..They were black black but i had the air fuel wrong..do u all really think this has to do with the gas..doesent it sound wrong for soemthing to be going at a little over 200 hours
 
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Re: 5.0 Mercruiser Smoking

so ur saying that it could be the risers making this smoke? what i put on captains choice exhaust? would that take care of the problem if that was the case? does anyone know of a cheaper way to add thru hull exhaust to this boat? i called corsco i thinjk it is called and they wanted $1500 for the captains choice..thanks for all of you opinions
 

Scott Danforth

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Re: 5.0 Mercruiser Smoking

I am saying, if your manifolds and risers are shot, you need new manifolds and risers. captains call, or corsa exhaust is after the manifolds and risers. heck, you could put a gold plated system after the manifolds and risers and it wont fix bad manifolds and risers

if your plugs are black, you are way too rich and you are washing your cylinder walls down with fuel and the motor is eating itself.
 
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Re: 5.0 Mercruiser Smoking

I am saying, if your manifolds and risers are shot, you need new manifolds and risers. captains call, or corsa exhaust is after the manifolds and risers. heck, you could put a gold plated system after the manifolds and risers and it wont fix bad manifolds and risers

if your plugs are black, you are way too rich and you are washing your cylinder walls down with fuel and the motor is eating itself.
Thanks for the advice..i am glad that it is the end of the season so i can tear this thing apart..once i get them off how will i be able to tell if that is the problem or not? i know that is the case if there are cracks but what am i looking for besides that? what is a tell tale sign? thanks again for all of your help everyone
 

04fxdwgi

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Re: 5.0 Mercruiser Smoking

Thanks for the advice..i am glad that it is the end of the season so i can tear this thing apart..once i get them off how will i be able to tell if that is the problem or not? i know that is the case if there are cracks but what am i looking for besides that? what is a tell tale sign? thanks again for all of your help everyone

Could be something as simple as a crappy gasket between the manifold and riser, leaking water into the exhaust stream before the riser, but you won't know till you pull it all apart and look.

Leave the "Captain's Call" idea for later unless you just want to spend the cash for loud exhaust, as it will do nothing to fix your "problem", if there is one.

At this point I am wondering if you are just seeing normal exhaust steam while running and perhaps a pro should be checking it, as there seems to be a lack of mechanical knowledge attached to the wrench and that is where things can get broken more than fixed.
 

series60

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Jan 4, 2010
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Re: 5.0 Mercruiser Smoking

17 hours average of run time a year isn't very much. Rings gum up and start to stick. Slug can build up everywhere oil travels. You live in a high humidity area which will add to the slug build up in addition to the lack of run time. Have you run the engine WOT for a little while to get the engine good and warm in those 17 hours a year? Water in the slug will evaporate once the engine is up to running temp and will produce some whitish smoke as the water evaps. What is the engine temp during a hard run and after returning to idle. What type of carb -2-4 bbl?
 
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