Stuck Valve on an Iron Duke??

[SHickey]

Hello,

I picked up a project 21' '74 Mirrocraft that has a Mercruiser 140 (iron duke) and a MC-1 outdrive. I know very little about this boats history so when I started the motor for the 1st time it ran really rough and I could not get it to idle down. I checked the plugs and they seemed fine so I got some new points, rebuilt the carb and before I started it again, I wanted to check out the valve and make sure they were adjusted properly.

After I removed the valve cover, much to my surprise, I discovered the rocker arm on the very first valve (front to the back) was knocked off of the valve stem. Further inspection revealed the valve is stuck in the open position because the spring is compressed.
Is there anyway I can unstuck this valve from the top of the head or must I remove the head to inspect the valve and see why it is stuck in the open position. I am a little concerned to remove the riser and manifold off of this motor due to it's age and rust that is present on the motor.

Any help with this situation would be most welcome!!

 

[alldodge]

Hello,

I picked up a project 21' '74 Mirrocraft that has a Mercruiser 140 (iron duke) and a MC-1 outdrive. I know very little about this boats history so when I started the motor for the 1st time it ran really rough and I could not get it to idle down. I checked the plugs and they seemed fine so I got some new points, rebuilt the carb and before I started it again, I wanted to check out the valve and make sure they were adjusted properly.

After I removed the valve cover, much to my surprise, I discovered the rocker arm on the very first valve (front to the back) was knocked off of the valve stem. Further inspection revealed the valve is stuck in the open position because the spring is compressed.
Is there anyway I can unstuck this valve from the top of the head or must I remove the head to inspect the valve and see why it is stuck in the open position. I am a little concerned to remove the riser and manifold off of this motor due to it's age and rust that is present on the motor.

Any help with this situation would be most welcome!!

You might be able to smack the top of the valve with a mallet and free it up, but if it was mine I would pull the head. Anything that makes a valve stick is not good and can only cause more problems later.

 

[GA_Boater]

I was going to suggest the mallet also. But it isn't a good idea because the usual reason a valve sticks is either the stem is bent or the stem is rusty. Both will tear up the valve guide and lead to more problems down the road. The head should come off.

The rusty manifold and riser need to be addressed as well. Rusty lumps usually don't last very long before causing more serious problems.

Good luck on whatever you do, SH.

 

[Fishermark]

I agree with the above. Even if it entails some work getting the rusty parts off, it is going to be worth it if for no other reason than you will have new bolts, etc to work on in the future.

Also - you ought to avoid calling the engine an "iron duke." This engine is not the same as the auto engine with that nickname. It can cause confusion when it comes to ordering parts. One man's definition of an "iron duke" is different than another's. Just sayin'!

 

[SHickey]

Thank you all for your responses. Every time I hope for an easy fix, I usually end up with needing to remove components off of the motor which sometimes leads to even more problems.

I am thinking about soaking the valve stem it with some penetrating oil, and wacking it with a rubber mallet to see if I can free it up. If I get it free and get the motor started, I can see if the outdrive works and also try to get the tilt/trim working. If I can get those three components going then I would still end up removing the head and addressing the valves.

Since I do not plan on having this boat in the water anytime soon considering the interior is in the process of being gutted, hopefully I can address the rusted bolts on the riser and manifold with some penetrating oil and some TLC.

Would heat from a propane torch be advisable for these rested nuts and stems or should I avoid using heat on these components??

Thanks again and I will call the motor a 140 instead of an Iron Duke to avoid any confusion

 

[Fishermark]

You can also call it a 3 liter - or a 3.0.

Heat will not hurt - I don't know if it will help or not. You usually need acetylene or perhaps even mapp gas. A good soaking with some PB Blaster in the meantime may help.

When you have run it - did you use muffs? Or run it without water?

 

[SHickey]

I always use the muffs since I rune it in my driveway. I also checked the intake hose from the lower unit to the motor to make sure it was pumping a good stream of water. I will also replace the impeller when and if I get everything else going. Who knows how old that thing is??

And yes, I will give it a good soaking before I try to remove any bolts.

Thanks again!!