late 60's mercruiser 120 didn't start... so I started

[plummadrumma346@cs.com]

1st up thanks,.. lotta helpful info in here. Boat was free,so hooked up hot battery & nothing, motor sat for 9 yrs, so lubed cyls w/ w-d,& w/ very little effort it freed up, had fire but wouldn"t start (but it sure was trying).Checked comp 2cyls blew thumb out & 2 didn"t. I poured in a little oil, & all had comp,till oil was gone, so i pulled head & 2 valves (small valve on 3rd & 4th) appear to be worn at an angle & look like they arenT seating also the exhaust manifold was bad especially #3,rust was so thick I scooped it out w/ finger. 1&2cyls look ok,3 has rust in exhaust manifold& under head, 4 looks ok no cracks as far as i can c, what do u suspect? & what next? thanks guys. p.s. head gasket doesn't look blown.

 

[Buttanic]

Re: late 60's mercruiser 120 didn't start... so I started

Time for a rebuild. Sounds like frozen or broken rings in 2 cylinders and in need of a valve job. No easy way, it sat up too long.<br /><br />Buttanic

 

[plummadrumma346@cs.com]

Re: late 60's mercruiser 120 didn't start... so I started

Thanks buttanic, haven't had time,but now that head is off I should be able to tell if rings are broken, right?When you say rebuild, how far down do you suggest, & I read that this motor is compatible w/ the chevy 11 153 c.i. Would napa carry parts?There thats my 4 question limit for today, if I don't limit my ?'s,I won't stop. thanks for your time&help.

 

[Bondo]

Re: late 60's mercruiser 120 didn't start... so I started

It sure Sounds like that motor needs to see a Machinest before it's Ever going to Run......<br />For a Complete Rebuild....<br /><br />Yes,<br />NAPA carries All the parts you'll need......

 

[SS MAYFLOAT]

Re: late 60's mercruiser 120 didn't start... so I started

There is no way that you can tell the condition of your rings are in with just the head being removed. Engine must be removed and put on a stand. Then you must acces the crankshaft by removing the oil pan. Remove the connecting rod cap and push the piston out of the cylinder. Of course the head must be off.<br /><br />How much rust is on the cylinder wall? If it is pitted too bad, boring out the cylinder may not remedy your problem. Then you will need a different block. A machineist can confirm if it does or not. If has to be bored out, you will need a complete set of new pistons/rings.<br /><br />While you have the rod cap off, use plastic guage to check the clearance in your rod and crank bearings.<br /><br />I tend to think like the other experienced mechs here, "Its time for a rebuild or just use that as a core for a rebuilt". It is possible to find a good engine of that size fairly easy.<br /><br />I had the same engine that I rebuilt several years ago. Bored/new pistons, crank turned/new bearings, head rebuilt/new valve train, and new oil pump. This cost me about $650 with no warranty since I did it myself. Engine performed very well afterwards.<br /><br />The time involved to haul the stuff to the machine shop, finding parts, and mess in the shop is not worth it to me again. From now on if I need a new powerplant, I get a rebuilt with a warranty. Good Luck

 

[plummadrumma346@cs.com]

Re: late 60's mercruiser 120 didn't start... so I started

cylinder wall w/ the rust isn't bad,filled cyl w/light oil & w/ old shop vac w/ somebodys old sock over end of wand, I removed the bits of rust & wiped down wall w/ soft cloth & surprisingly looks good, no gouges, w/pitting at a minimum, very faint, The majority of rust was in manifold & the head & cyl looks like 3 very faint spots towards top of cyl wall. The rest of cyls look good, no scorched walls, gouges or pitts.My nephew has a machine shop & could get head done for free, if i remind him of that time when i bailed him out of the pokie.Is there some sort of check valve?? in exhaust system, that might have also failed & allowed h2o to enter cyl??,I was going 2 order manual, but would appreciate a recommendation on a good, complete manual before I order 1 thanks again!

 

[Fishermark]

Re: late 60's mercruiser 120 didn't start... so I started

I personally enjoy rebuilding engines, so for me, the time and labor involved isn't an issue. But that's me. What about you? At this point you need to sit and figure the cost involved in a rebuild versus a rebuilt or even used engine. The head may or may not be salvagable -- the block may or may not be salvagable -- by your description, I certainly wouldn't want to put that manifold or elbow back on a rebuilt engine (and manifolds are expensive). The water and fuel pumps should be changed as they will most likely leak from dry rot. The carb will need to be rebuilt... In short, not much could be / should be reused on an engine that has been sitting that long. You may be far better off finding another complete engine.