kenmyfam
Supreme Mariner
- Joined
- Aug 10, 2006
- Messages
- 14,392
I have just been given a Mercury 7.5 twin cylinder in several pieces. It is all there and appears to be in good shape except 1 piston is scored in a quarter inch wide area about 0.015" deep. from about half way up to the lower piston ring. The previous owner started the disassembly and has since bought a replacement motor due to the upcoming season. His story is as follows.
Out trolling with this motor running, storm coming in on the lake so he fired up the main motor on his 24ft Sea Ray leaving the trolling motor running. Gunned the boat back to the marina to beat the storm with the trolling motor still running. This apparently starved this motor of cooling water and it overheated. When he stopped at the marina the trolling motor cut out. He tells me that it would still start but would not idle at all.
My plan is to replace water pump assembly and thermostats (if it has any) either replace the piston or repair, new rings,the bores appear fine as regards damage but I have not checked them for roundness or concentricity yet. I will rebore myself if necessary. Then put it all back together and try it out.
The serial number is 7206318 and it has a blue band around the hood. Can anyone help identify the year, model etc or give me a link to where I can trace it myself ?? I have always had Johnson / Evinrude to this point so am pretty dumb with Mercury products !!! I will then get a manual for this little motor and hopefully have myself a reliable little troller for the season. Trolling with my Johnson 140hp just does not cut it !!!!
Thank You all in advance for any and all information and advice you can give.
Ken.
Out trolling with this motor running, storm coming in on the lake so he fired up the main motor on his 24ft Sea Ray leaving the trolling motor running. Gunned the boat back to the marina to beat the storm with the trolling motor still running. This apparently starved this motor of cooling water and it overheated. When he stopped at the marina the trolling motor cut out. He tells me that it would still start but would not idle at all.
My plan is to replace water pump assembly and thermostats (if it has any) either replace the piston or repair, new rings,the bores appear fine as regards damage but I have not checked them for roundness or concentricity yet. I will rebore myself if necessary. Then put it all back together and try it out.
The serial number is 7206318 and it has a blue band around the hood. Can anyone help identify the year, model etc or give me a link to where I can trace it myself ?? I have always had Johnson / Evinrude to this point so am pretty dumb with Mercury products !!! I will then get a manual for this little motor and hopefully have myself a reliable little troller for the season. Trolling with my Johnson 140hp just does not cut it !!!!
Thank You all in advance for any and all information and advice you can give.
Ken.
