1979 80 hp mercury

[chuckharwell]

The details:<br />129 compression on 3 of 4 cyl.4th I couldnt get to./I pulled the plugs and the top 2 are clean but the bottom two were smokey./It runs fine out of the water but when I put it in the water it started and died then wouldnt restart. I noticed water leaking around the 3rd sparkplug. This is a new boat for me and I am not sure what to do next. I recently overheated the motor due to a bad impeller which I just replaced. The compression is consistent still so I am not sure if the headgasket is blown, the block is cracked or what?? Thanks for the help

 

[mellowyellow]

Re: 1979 80 hp mercury

no way to know what damage occured without tearing<br />her apart. water intrusion is prob. head gasket,<br />but u never know.<br />good luck,<br />M.Y.

 

[corm]

Re: 1979 80 hp mercury

Hi,<br />Your motor has no head gasket. The back water jacket needs to be replaced after you get it running. My guess would be that you warped the exhaust plate and gasket which are inside the exahaust plate cover and cool the exh port. When it is bad is will spray water in to the cyl and make the plugs look like you washed them clean. Get the mter to run on a muff at a fast idle 1500-1800 rpm then turn off the key. Quickly pull the plugs and look for water beads on the sparkplugs. This is the bad sign your looking for. If you have it, then you will need to replace the above parts.