'73 140 MC

[DBHOSS]

I have an 18' deep V seaswirl with a 140 hp Mercury Mercruiser. It runs just fine but all of a sudden it started knocking. I have changed the push rods and lifters. This gave no change. I have adjusted the lifters. This stoped he noise for a few minutes, then it came back. I then pulled the plug wires one at a time. It soped when I pulled #1 plug. Doesthi mean I have a piston rod going? What needs to be done to fix this with out a rebuild. It is real dificult finding parts for this old of a boat. If I do find the parts, they are not cheep. Anyone who may have an idea please let me know.

 

[12Footer]

Re: '73 140 MC

Greetings, Hoss,and welcome to iboats.<br />Yes, it does sound like bad news. Probably the wrist pin,rod bearing, or crank itself. Usually, if caught in time, you can rebuild cheaply enough. But if it has been doing this for 5-10 minutes, it can demolish the crank,piston,jug, or even send the whole shootin match thru the block (eeewww).<br />A compression test could tell you more, but it's a good bet it's tear-down time.Sorry to say..

 

[DBHOSS]

Re: '73 140 MC

Thanks fo the reply. It may not be what I wanted to hear. I did have to run it for 20 minutes or so to get back to shore. Then I ran it on and off a few minutes running more tests. I hope I have not damaged it too bad. This motor I have been told is the 'OLD IRON DUKE' andis hard to find. If the moto runs just fine except the knock. Is there a chance I can just replace the rist pin lie you said? How can I tell or not? If this is not possible, is there another motor that will bolt up to the out drive? Possibly a V6 or 8?<br /><br />Thaks again