Replace yanmar camshaft seal

[Quixotic]

Can anyone tell me if it's possible to replace the camshaft seal on a yanmar 3gm30f without removing the timing gear cover? Is it possible to pry it out the press it back in with a socket and hammer?

[a64pilot]

I am not familiar with that motor, but you should be able to look at it and tell, it's unusual for a seal to press into a cover from the outside, I'd be real surprised if you could.

[a64pilot]

If you can, as opposed to prying it out I've had good luck with drilling two small holes, screwing in sheet metal screws and pulling the seal with safety wire. Be careful not to drill too deep of course.
If you can find a manual or parts breakdown, often they will depict with a dotted line how the seal is installed if it's not explained in the manual.

[four winds]

I have the same engine and the manual. I have not replaced this seal however.

Looking at the cutaway diagram of the engine one thing is clear. The seal is actually recessed into the outer surface of the gear case. Under the cup shaped cover as I'm sure you know. Two screws securing the cover.

The end of the shaft protrudes into this cover. However, there is something not clear to me. On the end of the shaft is "something" else. Hard to identify in the cutaway. But larger in diameter than the shaft and seal.

Looking at the disassembly section doesn't help. The cupped cover isn't mentioned and may come off with gear case cover. The drawing is at the wrong angle to tell. But the cam shaft end is visible and free of any other part in a drawing suggesting the case cover had just been pulled free.

It appears to me that the cupped cover can be removed without harm. Then this unidentified part would be visible. With the seal directly behind and removable depending on this "wtf is it part".

I'll take a pic of the cutaway if you like and the disasembly pic.

But it's not going to hurt anything to pull that cupped cover and look.

[four winds]

Well, I read the text in the manual.

That cover is called the "starting shaft cover". Behind it is a "bolt with hex socket head" and a "pin for handle fitting".

So remove the cover, the hex socket bolt, and the pin. Then Bob's your uncle.

These same steps are required for removal of the gear case anyway.

I say go for it.

Take care to note the angle of the lip on the seal.

[four winds]

So the "wtf" is a crossection view of a bolt in the end of the shaft holding a pin through the shaft also in crossection.

Hope this helps.

[Quixotic]

Thank you for the replies everyone. I will try and do it without removing the timing gear cover. I removed the shaft cover when I noticed an oil leak coming from behind it. On my engine the alt belt rises straight up from the crankshaft to the fresh water circulation pump and goes right in front of this cover. As such it's not really feasible to hand start the engine so I have no pin in the shaft. The hole/sheet metal screw idea sounds great! Next opportunity I have to get a new seal I will give it a shot!

[Quixotic]

Four winds, when you mention the angle of the seal are you referring to which way the seal wipers, so to speak, are facing? Fore or aft?

[four winds]

Originally Posted by Quixotic

Four winds, when you mention the angle of the seal are you referring to which way the seal wipers, so to speak, are facing? Fore or aft?

Correct, the edge that touches the smooth surface of the camshaft must angle the same as the one removed to work correctly.

I wondered about the belt being in front of this as well. I'd like to see a factory start handle. Could be these engines are used in industrial applications with no alternator.

I had a British three cylinder motorcycle with an engine originally designed for generators.

[Quixotic]

Yes I think you are right about this engine being used in other applications as well. I read somewhere that they are used in agriculture in Asia. Also, the raw water cooled version has a different belt routing. The pics I have seen of the 3gm30 have no circulation pump and the belt goes straight to the alternator. I guess these could be hand started.