anybody know why???

[howster]

i have a 87 model 75hp mariner (dont have heads)<br />i have a bad thermastat and a busted diaphram leaking water around the plugs no water in cylinders thow gonna change gaskets to can any of these problems cause engine to pop and sometimes back fire any help is great help thanks

 

[Hooty]

Re: anybody know why???

Well, lets see. You have a 1987, 75hp Mariner. I got that. I don't get the "dont have heads" part. The thermostat is bad and a diaphragm is leaking water around the plugs. What diaphragm would that be? There's no water in the cylinders but you're gonna change the head gaskets anyway. Your question is "can any of these problems cause the engine to pop and backfire"?<br />Usually popping and backfiring is caused by either a lean mixture, a timing problem or cylinders cross-firing. If there's enough water around the plugs to short them, it may cause it to pop and backfire.<br /><br />c/6<br /><br />Hooty

 

[howster]

Re: anybody know why???

does this engine have heads? serial # is ob13o551<br />the diaphram that sit right on the back of the motor by the plugs. in the housing thats where the thermastat and the pressure release valve is diaphram is on the pressure release valve wheres the others?<br />thanks hooty

 

[ob]

Re: anybody know why???

The engine has what Mariner refers to as a cylinder block cover.Behind it is the piston heads.That is the cover that the T/stat housing and poppet valve assy. is bolted to.The poppet valve has just one diaphram.This is the only diaphram related to the cooling system.<br /><br />Not clear on exactly what you need to know.Water leaking from the T/stat cover onto the sparkplugs can most definately cause a misfire.