4.3XL Merc steam/smoke from Valve Covers

loriaw1

Recruit
Joined
May 16, 2005
Messages
5
Sorry if this has been asked already...New to the forum<br />A little background<br />-Currently have a 97 Glasstron w/ 4.3XL merc in it<br />-Last 2 trips out...it was missing at 4k rpm's or so, Deciced to tune it up W/ plugs, fuel pump and fuel seperator. All purchased from a boat shop. Also dumped a can of Seafoam in the gas tank, though maybe it would loosen up some crap and flush the eng...<br />Now the problem:<br />-After all maintenance, I developed a knock/loud tick! can't pinpoint it even w/ a steath-a-scope. The shop said to bring it in...they looked at it...said that the merc 4.3L have a known issue w/ the piston skirt being loose and rattling? After replacing the Plugs?<br />-Also have a Steam/smoke, phrased this way because it doesn't smell, comming from both valve covers and going into the spark arrestor.<br />-I drained all gas and used only 5 gallons of 91 octaine,can't get above 3500rpm w/o it cutting out. Almost seems as if the Steam/Smoke is choking out the intake?<br />Any help would be appreciated<br />Later<br />Bill
 

xltier

Chief Petty Officer
Joined
May 20, 2004
Messages
636
Re: 4.3XL Merc steam/smoke from Valve Covers

good chance that your 4000 rpm miss has festered into something more now.maybe just coincidence. you should do a compression test to find the source of the smoke.start with the back cylinder on the drivers side.thats where ive seen trouble before.head gaskets dont usually make noise.look at your old plugs and see if there is any specks of aluminum stuck to the porcelain.thats usually associated with piston damage.
 

Don S

Honorary Moderator Emeritus
Joined
Aug 31, 2004
Messages
62,321
Re: 4.3XL Merc steam/smoke from Valve Covers

Any of the old plugs look brand new? I mean shiny like they have never been run? Or rusty ? Either would indicate water getting into the cylinder. Would cause steam and a miss.
 

loriaw1

Recruit
Joined
May 16, 2005
Messages
5
Re: 4.3XL Merc steam/smoke from Valve Covers

No the old plugs appeared in good condition, just a little oil residue...but nothing to cause alarm. I'll do compression in the morning. Also, dont't think it's an H2O leak due to oil on the dipstick looking fine. But?
 
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