Crankshaft Question / Rebuild

[Swampmouse]

I am just now getting my motor (1973 Johnson 115) put back together and have a question on the crankshaft.

I always thought the crankshaft made a full revoloution in the crankcase?

However, now that I have put mine back in the crankcase half and lined up the hole on the center main bearing with the pin in the case so that it doesn't move, the crankshaft only rotates 180 degrees and feels like it is hitting something and then going back the other way does the same thing.

Can someone please tell me if that is normal or is something wrong here???

Also, one more thing - The Seloc book I have says that when putting the rod caps back together, they must be absolutely perfectly fitting "without even a whisker of a lip on either side" so that a sharp object will not grab when rubbed on the break. However, the one I was working on tonight absolutely will not get 100% perfect - it gets very very close, but not perfect. How true is what the book is saying?


Thanks,
SM

 

[MJ76]

Re: Crankshaft Question / Rebuild

Did you have the powerhead rebored for oversize pistons? I was putting one of these together a few years back and the shop that did the machine work didn't run the bore deep enough, so as a result the oversize pistons would bottom out in the block, like you're describing. Either way, you have a problem. The crank only turns one way, and it's got to go all the way around. As far as the rod caps, are they matched to the rods they came off of? And how close is close?

 

[samo_ott]

Re: Crankshaft Question / Rebuild

I was putting a smaller engine together a year or so ago and put the pistons in backwards (duh!) so the crown hit on the revolution, so I had to take it apart aand reverse them. Dunno if that's the problem.

 

[micel]

Re: Crankshaft Question / Rebuild

Dont force it, it shoud go around both directions,but when running of course only one direction.MJ76 experience is quite common,and he is right on about the rest.

 

[Dhadley]

Re: Crankshaft Question / Rebuild

Keep this in mind -- the 73 V4 is a one-of-a-kind deal. The block, crank, rods and pistons are for 1973 only. Not 72 and not 74. All the parts must be for a 73.

Start from the begining and tell us exactly what you replaced. All the pistons or just one? Same crank and rods?

Now, think of the next scenario -- at some point in the last 30 years someone repalced the complete powerhead. A 115 powerhead (complete) from 1974 to 1976 will bolt on and work fine. You just have to keep all the powerhead components the same.

 

[Swampmouse]

Re: Crankshaft Question / Rebuild

Sorry guys - I mis-typed. I should have said 1983 model (it was late). I had not yet connected the rods so it could not have been the pistons hitting the cylinder. I will try to take a look later tonight and see what's going on. I thought it was very strange - fit into the powerhead like a glove, then only 180 degrees in either direction.

I will post up what I find.

Thanks,
Sm

 

[Swampmouse]

Re: Crankshaft Question / Rebuild

ok - great news. The crank was just hitting the rod ends down in the bottom. Tomorrow I will get her all put back together .

As for the rod caps, thet are going onto the ronds from whence they came. The alignment is off just enough to make your fingernail grab on it - pretty darn close, but not perfect - but I do not know if perfect really is possible???

Thanks,
SM

 

[jimmbo]

Re: Crankshaft Question / Rebuild

Perfect is not only possible but required. If the outer surface grabs your your fingernail, the bearing surface will grab the roller/needle bearings as they move. There is a tool used by service techs to position the cap properly

 

[Dhadley]

Re: Crankshaft Question / Rebuild

You do line up the dots, right?

 

[Swampmouse]

Re: Crankshaft Question / Rebuild

Yeap, dots are lined up. Ok, if perfect is possible, I will play with her some tonight. I didn't want to waste time getting it perfect if it wasn't possible. Now that i know that it is, I will give it a whirl.

Thanks for the info guys!

SM

 

[noelm]

Re: Crankshaft Question / Rebuild

trust these guys advice the rod caps will need to be perfect, I remember when I did some OMC training way back, I think we used a really sharp pencil, and if you could feel any "notch" when moved over the rod cap join, we had to refit untill perfect, from my vague memory, they were what was called "cracked joint" which means the rod is machined in one piece (of course) then it has a small notch ground into it and the joint is then "cracked" so it MUST fit back axactly as it was.

 

[Dhadley]

Re: Crankshaft Question / Rebuild

If you ever have one that just gives you fits, move it over from the crank and put the cap on. Put the cap on just like you would if it were on the crank and without a bearing inside. Line it up as best you can and then look at the inside where the bearing would be. The joint must be abasolutely perfect inside where the needles roll.

If the outside won't line up it probably means the inside isn't lined up. If you can't get it to line up you'll need another rod. Sometimes they just won't line up. It's rare but it happens. Remember, it's nice to have the outside line up but the important thing is to have the bearing surface line up.

 

[Swampmouse]

Re: Crankshaft Question / Rebuild

Thanks for all the info guys.

Ok- here's the update. The reason it wasn't alining as I discovered this afternoon was that when I took them apart a few weeks ago, I labeled the ziploc bags from both bottom pistons as "bottom left"! So, of course I grabbed the first bag labeled "bottom left" and it was really for the bottom right! Once I discovered this it was smooth sailing from there on. I got all 4 perfectly matching.

Naturally, as with almopst every big project I undertake....when I went to torque down the cap bolts, I discoverd that my 1/2" drive torque wrench only goes down to 50 pounds (this was after I went on the way home and bought an 1/2" X 3/8" adapter so my 5/16 socket would work with the wrench), so now I will have to go tomorrow morning and buy a smaller torque wrench as they are to be torqued to 30 ft lbs only -oh well. The story of my life.

How about all the new gaskets I am about to put on??? Should I put some of the gel sealer on each side of the gaskets before I install them? The book mentions to do it on the exhaust gasket, but doesn't say about it on the others...head gasket, reed box, bypass gaskets, etc.??

Thanks,
SM

 

[Swampmouse]

Re: Crankshaft Question / Rebuild

Anybody got thoughts on the gel?

Thanks,
Sm

 

[funpilot]

Re: Crankshaft Question / Rebuild

Don't use Gel Seal on the gaskets, it's only for the non-gasketed crankcase halves. Use the OMC (Bombardier) Gasket seal p/n 508235 or Loctite Aviation Sealant 30517on gaskets. They come in a can with a brush in the lid and cures pliable.

good luck,
fp

 

[MJ76]

Re: Crankshaft Question / Rebuild

Except for the head gaskets.

 

[funpilot]

Re: Crankshaft Question / Rebuild

Oh... Good catch MJ. Yep, the head gaskets go on dry.