Big Twin Crank seal

[byacey]

Feeling ambitious I decided to replace my upper crank seal on my '69 40HP. After drilling two 1/16" holes in the seal I threaded two #6 sheetmetal screws into the holes and proceeded to tear the seal to little bits of metal trying to pull it out. Then I resorted to the tactic of wedging a small, thin screwdriver between the outside edge of the seal and the sleeve the seal sits in and carefully crushed the seal all the way around to loosen it up for removal. finally got it out. The rubber portion of the seal seemed to prevent any of the little metal chips from falling down into the cranckase, but if a few did happen to fall in, and with luck not get stuck in the top bearing; what are the chances of them passing out of the engine, or are they going to eventually make their way down to the lower bearing and initiate self destruct sequence? Should I tear down the block? Also, if the new seal is bottomed in the ring, is it too close to the bearing?

 

[R.Johnson]

Re: Big Twin Crank seal

There is a tool made to properly remove, and replace that seal. I have seen more than one home made attempt end in disaster. As for the result, your guess is as good as mine. "Adjust for least metal shavings in exhaust" Not bad advice.

 

[F_R]

Re: Big Twin Crank seal

IF anything fell down in there and managed to make it through the bearing, it would be expelled out through the cylinder. It cannot go all the way to the bottom or even get into the center bearing. The big IF is whether it makes it all the way through unscathed. Who knows? Personally, I wouldn't tear the powerhead down on an unlikely maybe. But that's your choice.

 

[byacey]

Re: Big Twin Crank seal

Well, I took my chances and went out to the lake. It certainly idles much better and at a slower speed, 500RPM . Last year I fixed the threads for the screw that holds the point gap in adjustment. When I went to readjust the points it tore out the JB weld that I used, so I retapped the hole for 10-32 threads and cut down a 10-32 macine screw to the right length. There isn't a lot of thread depth here, so one has to be careful. It appears my WOT RPMs have gone up about 200RPM, but I would attribute this to the timing being closer to what it should be due to the points being properly adjusted.

 

[rwash91]

Re: Big Twin Crank seal

Why did you change the seal in the first place?? Was it leaking oil bad or just not idling right. I am curious to know because I have a engine that really dosn't idle to good and have thought about that seal alot !!

 

[byacey]

Re: Big Twin Crank seal

Yep, poor and unreliable slow speed idle. Now it idles like a champ, I can even troll with this motor now! It'll idle without any attention for well over an hour now. Before It would go for 5 minutes and bog down and quit. There was a film of oil all over the armature plate and flywheel.

 

[rwash91]

Re: Big Twin Crank seal

I have a thread on here named 140 rude. I have discused raising the engine on the hull a bit and I have already ordered a new crank seal for mine also. I hope to also be able to idle for long periods also ( catching shad with a throw net). I'll be giving her a try hopefully by weeks end.