Mercruiser V8 With Broken Push Rods on Cylinder #2

[gregpatent]

I have a remanufactured Mercruiser 305 that started making a clanking sound when I was returning from a 5 mile fishing trip at the mouth of the Cape Fear River. The engine is 2 years old, so it is out of warranty. I have low compression on #2 cylinder, so I pulled the valve cover. Both push rods on cylinder #2 are broken. I may have stuck valves on that cylinder (the other push rods look okay and the rest of the cylinders have good compression). There is no water in the oil. Here is what I plan to do: 1) remove the intake manifold to get the rest of the pieces of the push rods out; 2) remove the cylinder head, take it to a machine shop, and have them fix the valves. Does this make sense? Any recommendations?

 

[Bondo]

Re: Mercruiser V8 With Broken Push Rods on Cylinder #2

Ayuh,... That sounds like a reasonable path...

 

[John_S]

Re: Mercruiser V8 With Broken Push Rods on Cylinder #2

I am bit surprised that the pushrods broke into pieces. Usually they bend, rocker arm pushed to the side, or pull the stud in the head, etc. No water in the cyl? Probably will know more when head is off.

 

[gregpatent]

Re: Mercruiser V8 With Broken Push Rods on Cylinder #2

Any tips on removing the intake manifold. I have removed all of the 9/16 bolts, the distributor, ignition coil, wires, etc. My manual says, "pry off intake manifold." Don't want to damage any gasket surfaces. I tried pulling up on the front and back through the water intake and distributor holes, but it wouldn't budge. I thought of making something to go between the two thermostat housing bolts, screwing them in, and prying up on those with a crow bar on something inside the boat. Any help is appreciated.

 

[Bondo]

Re: Mercruiser V8 With Broken Push Rods on Cylinder #2

Any tips on removing the intake manifold. I have removed all of the 9/16 bolts, the distributor, ignition coil, wires, etc. My manual says, "pry off intake manifold." Don't want to damage any gasket surfaces. I tried pulling up on the front and back through the water intake and distributor holes, but it wouldn't budge. I thought of making something to go between the two thermostat housing bolts, screwing them in, and prying up on those with a crow bar on something inside the boat. Any help is appreciated.

Ayuh,... Gently, use a prybar at the corners, til 1 of 'em gives up....

 

[Stamey]

Re: Mercruiser V8 With Broken Push Rods on Cylinder #2

The corners are what I usually use, as Bondo said, but the gaskets at the end of the intake, front or back, are cork or rubber, and are pretty thick. You'll be replacing them anyway so if necessary take your screwdriver/prybar and, if it won't push in enough to get a bite, tap it with a hammer. The screwdriver will take out the gasket but not harm mating surfaces.

Chris

 

[John_S]

Re: Mercruiser V8 With Broken Push Rods on Cylinder #2

The corners are what I usually use, as Bondo said, but the gaskets at the end of the intake, front or back, are cork or rubber, and are pretty thick. You'll be replacing them anyway so if necessary take your screwdriver/prybar and, if it won't push in enough to get a bite, tap it with a hammer. The screwdriver will take out the gasket but not harm mating surfaces.

Chris

Stock mercruisers don't use the cork or rubber end gaskets. They use a heavy duty rtv, which is probably causing some of the removal "fun". Don't replace with cork/rubber. Use the RTV spec'ed in the merc SM.

 

[jerryb1]

Re: Mercruiser V8 With Broken Push Rods on Cylinder #2

and do make sure you have all the bolts out!

 

[gregpatent]

Re: Mercruiser V8 With Broken Push Rods on Cylinder #2

Got it off, removed the head, and was not surprised to find rusted intake and exhaust valves on cylinder #2. It seems they were both rusted shut, which I guess could have caused the push rods to break trying to open them. There was currently no water in the cylinder, but there obviously had been water there at some point. Cylinder wall was smooth and rust free. I took the head to the machine shop for a valve job. The exhaust ports on the exhaust manifold were rust free. However, the intake port on the intake manifold adjacent to cylinder #2 was rusted. The exhaust manifolds are 2 years old, and have never overheated. The intake manifold, however, is at least 10 years old and has been run in salt water before I installed a closed loop cooling system. The machine shop is trying a pressure test on the intake manifold. I think the water may have come from a rust hole or crack inside the intake manifold. My mechanic thinks the closed loop cooling system is causing the water intrusion. I hope it is the intake manifold so I do not have take off my expensive closed loop system. (It is actually a half system where the raw water goes throught the manifolds and a heat exchanger, but protects the engine.)