Is a broken pushrod bad?-gctid394490

[Guest]

Ok let me explain this, I have a 1985 mercruiser 170, it runs but runs extremely rough, by rough it shakes the whole boat badly lol. did a compression check all cylinders but 1 at 120ish the other at 0, I believe the bad cylinder is the #2. it is 2nd from the rear of the engine, added oil to the cylinder no change, pulled the valve cover and as I am looking at the rockers for that cylinder hoping its just a bad valve I noticed a broken pushrod for the next one forward counting from the rear, it would be the 5th pushrod from the aft forward. I realize this engine is a different animal from most but arent the valves right above the cylinder exhaust and intake for that cylinder like all others, I guess I dont understand how a 4 cyl engine can even start with one 0 compression cylinder and one with a non functioning valve. I dont have a manual for this engine yet, I have one for just about every engine and drive system but this one including 3 for 1992 and up mercruisers, dont know how that happened I will have another beer and think about it

[Jim_Gandee]

The simple answer is yes, it's bad. But why did it break? Was the engine ever hydraulically locked? Is there any other damage to the engine? I'd drain the oil through a paint filter looking for metal and also cut open the oil filter, stretch out the pleats and again look for metal. If you do find metal the type/size will help you determine what has broken. A borescope will be a big help in determining the health of the cyls as well as what the plugs look like.

[Guest]

about it being bad I realize its not a good thing, I just traded for this boat so I am working on getting it running, didnt think about it being hydro locked and breaking a push rod, I was kind of hoping the previous owner did a valve job and over tightened the rockers and thats why I was getting 0 compression in 1 and a broken push rod in the other, The head looks flawless like it is newer.

[Guest]

bbruno wrote:
about it being bad I realize its not a good thing, I just traded for this boat so I am working on getting it running, didnt think about it being hydro locked and breaking a push rod, I was kind of hoping the previous owner did a valve job and over tightened the rockers and thats why I was getting 0 compression in 1 and a broken push rod in the other, The head looks flawless like it is newer.

Jim is probably right. I don't know anything about the 170 engines. The best bet would probably be making the oil checks that Jim suggested, plus pulling the cylinder head. You could be lucky and find that things aren't all that bad. But good luck. Griff

[iceclimber]

I'd be afraid to run that motor until I had pulled then head and had it evaluated.

[Guest]

Well i would not pull the head just yet. instead i would replace the push rod and adjust all the valves (or plunger dept lol). Then i would turn the engine over by HAND several times if all feels well then i would turn the key and see what happens. No sence pulling the head if you don't need to. Now i see this in some car and light tk from time to time and 90 percent of the time a push rod is the fix with no other repairs being needed.

[Guest]

Nh boater thats what I was thinking but I looked down where the pushrod goes and the lifter is out of the hole and I cant see the other end of the pushrod, uh ohhhh, gonna put a magnet in the area and see if I can find the pushrod end and get the lifter in place but I ordered a gasket set to probably rebuild

[bhawes]

The 5th pushrod from the rear would indeed be in the number 2 cylinder. I'd just pull the head and get it over with. There's bound to be some loose metal floating around down there, and you need to see what its done. Those engines are not difficult to take apart. Just be very careful when you reinstall the exhaust manifold. Know the torgue values, and do not exceed them. The casting on the head is very easily broken if you do overitghten.

[Guest]

found another bent push rod, this time on the 2nd cylinder from the rear the small valve which I believe is the intake and the valve was loose, it would move up and down aprox 1/16-1/8 of an inch before i hit resistance from the spring, in the 3rd cyl the large valve is loose which should be the exhaust valve and I believe was the valve with the broken push rod, it doesnt move as much but I had good compression in that cyl oddly enough. all the other valves are tight by hand, havent tried any type of feeler guage. cylinders and pistons look ok, no scoring or pitting. I may just hone the cyl and re-ring the pistons. head gasket didnt show any markings of leakage, no sign of water getting in the cylinder. thoughts?

[Guest]

oil seemed kind of milky, I think maybe the engine was hydro locked at one time and thats what bent and broke the push rods, I will pull each lifter and bleed them, should I be able to compress the lifters by hand a little?

[Guest]

on the 2 valves that were loose I just found that both had broken springs, WTF, 2 valves right next to each other in different cylinders had broken springs with bent or broke push rods, what could have caused that??? I have to admit I have only had chevy engines apart in various stages from replacing and adjusting heads and installing intake manifolds, a ford engine is a little strange to me even though they all have similar designs. just fyi I dont have a manual yet for this engine which I will get before reinstalling everything, I didnt want to spend the money on a manual and end up getting a different engine, wasnt sure I was going to keep the 170 but now I think I am. Basically I am looking for advise on what could have caused the failures and if it was something in the engine or something like a hydro lock from the flappers being gone (which they are)