mercury 500 half power

[miclea0317]

this is a new reply to my mercury 500 with half power. i finally got a chance to look at it good today and i realized that the bottom plug is milky when i pull it out. obviously water in that cylinder. but the question is how could it be getting in there? also i ran the motor out of the water for just a second after i cleaned the plug and made sure the water was out of the cylinder and it still ran the same, so is it the water thats making it run that way? i know its not a good thing and it needs to be fixed. Im not sure of the year, but i do have the serial number (3718059). if anyone can help i would greatly appreciate it, and also about how much for me to fix or a shop to fix. thanks alot.

 

[buttonhook]

Re: mercury 500 half power

blown head gasket?? maybe?? its what it sounds like.

 

[tmcalavy]

Re: mercury 500 half power

with that serial number, your outboard is probably a 74-76 model. being that you are in the carolinas, my first Q would be whether the motor was run in salt water. that can lead to mucho corrosion. if it has a saltwater history and corrosion present, you or a tech may not be able to get the head off to change a gasket...i can't remember if they even have one. for what you would spend, you might could replace it with a good used motor, or at least replace the powerhead entirely with a used one. depends on a lot of factors, chief being whether you can find anyone in your area that you trust to work on it and do it right. If the answer is No, consider a powerhead swap or a complete repower/replacement...you can do those with even a minimum of wrench experience.

 

[ledgefinder]

Re: mercury 500 half power

No head gasket on those, I think the Merc experts will tell you it's leaking in from the exhaust plate. Try John's Old Mercury board. I have a good '74 powerhead if it comes to that.

 

[miclea0317]

Re: mercury 500 half power

the motor doesnt seem to have a salt water history, im about 5 hours from the ocean. i have been told it cold be the exhaust plate from the mercury people in the area, also the water jacket for that cylinder. im just curious as to how much you would want for the power head you have. i was also wondering how much it would cost to fix the exhaust plate if thats the problem, and if it would be very hard. i would also like to know how to find out whats the exact peoblem with the motor without tearing it down. thanks for the help guys its the most i have got yet.

 

[tmcalavy]

Re: mercury 500 half power

Can't help much beyond what I've already offered. Hopefully an old Merc hand will see and take interest in this post and help with your last question. <br />If someone can't offer more help addressing how to diagnose the problem, you might try posting at John's old merc site at:<br />www.pfs-ware.com<br />that bunch has helped me a bunch with mine, as have the good folks on this fine board. good luck.

 

[12Footer]

Re: mercury 500 half power

Can't really add to what Tim posted. Pull the exaust port plates, and check the gaskets and surfaces for signs of leaking. Outside of a cracked block, this is where the problem is.<br />These plates warp extremly easily under normal conditions. But take the thermostat out and run it for a few hours, and it's a sure-bet, the plate has warped.<br />Usually, if the engine has not overheated or been run in cool water without a tstat, gaskets will fix it. In severe cases, the mating surfaces will have to be shaved flat again.<br />Make sure to follow tightning sequence and torque specs outline in the manual, or you'll be back.<br />Re-torque the plate bolts after your first trip out with it too.

 

[ledgefinder]

Re: mercury 500 half power

$150-175 if it checks out OK, I just took it in trade. 413-357-6372