Rod cap movement

[jbhasaboat]

OK the rod caps in my Evinrude 70 move up and down, flywheel towards lower unit movement, they don't move in out or out though, is this normal?

 

[boobie]

Re: Rod cap movement

Sorry, but I don't understand your post ??

 

[jbhasaboat]

Re: Rod cap movement

Sorry about that, guess it only made sense to me cause I was actually looking at it. Anyway, I ve taken the crankcase off to redo the crankcase seal and lower crank seal and while I had the engine apart I was going over everything and noticed that the piston rods on the crankshaft will move up and down on the crank. I can push the rods up and down along the crank journal, basically they have play on crankshaft but only up and down play, not side to side or forward and back. Hope this clarifies.

 

[kodibass]

Re: Rod cap movement

I think it goes side to side is OK up/ down NOT OK

 

[Grub54891]

Re: Rod cap movement

There is a slight amount of play on the crank boss. What you are saying is the play is side to side,inlie with the crank. That should be ok.
Grub

 

[F_R]

Re: Rod cap movement

If I am reading the post right, it is ok and normal. The rod will slide lengthwise on the journal. But now, I guess the question is just how much? I've never seen any specs on that. Lets just say it is not usual for it to be too much, if it were you would be seeing a lot more to worry about than that.

 

[schematic]

Re: Rod cap movement

If I am reading the post right, it is ok and normal. The rod will slide lengthwise on the journal. But now, I guess the question is just how much? I've never seen any specs on that. Lets just say it is not usual for it to be too much, if it were you would be seeing a lot more to worry about than that.

Very well said

 

[jbhasaboat]

Re: Rod cap movement

Well thanks guys I guess it is normal, it moves side to side like said and there's not very much movement. But seeing any movement on a piston rod scares me. Now Ive got another question, well more of an opinion to ask. The engine that I have open now to replace the lower crank seal has a fair amount of surface rust on the crank shaft, no other issues I know of except the rust, (It was sitting outside unprotected for quite some time) Now I have another engine same year same model and all that has a very clean and shiny crankshaft ( this engine blew a piston ring and damaged the bore badly leaving the crankshaft undamaged) Im thinking about swapping cranks, I see it as just unbolting the rod caps, swapping in the new crank and re torquing the rod caps, is it that simple or is there something I have overlooked for doing such a swap?

 

[schematic]

Re: Rod cap movement

Depend how much engine life you expect. I never liked putting bearings from one crank or rod to another, as the wear patterns don't match. That being said, if the bearings look good.....It will likely outlast you....mismatched or not.

If you want maximum life.....replace the bearings.

 

[F_R]

Re: Rod cap movement

In any case, never use bearings that aren't virtually perfect. No rust, pitting, flat spots etc allowed. And you MUST use a torque wrench to tighten them to specs. I believe it is 348-372 inch pounds, but verify that. Needless to say, you can't swap caps from rod to rod or turn them end for end. But you knew that, didn't you?

 

[jbhasaboat]

Re: Rod cap movement

That's what I was worried about, if the rods fit snugly now I would hate to swap it over and have them be loose on the new crank. I don't think the rust really effects anything just as long as the bearing surfaces are clean?? So I think I'm just gonna leave it be and not run the risk of messing something up. This engine doesn't have much time on the clock anyway the cylinder walls are scored up pretty bad, it still holds good compression though but I wonder how long that will last before the compression goes. So Im trying to patch it up with out spending much on it so it will hold me over for awhile.

 

[schematic]

Re: Rod cap movement

Even if you decide to reuse the bearings, its a good idea to replace the bottom ball bearing. Its prone to rust due to its location, plus it bears the weight of the flywheel and crankshaft.

 

[jbhasaboat]

Re: Rod cap movement

I was going to replace the bottom bearing but Ive run into a problem with the bearing cap bolts, they won't come out, the manual says their only torqued to 30 ft/ibs but I cant get them to budge I even used a breaker bar and get no where. I don't want to force them too much because snapping the heads off one of those would equal a very bad day. Either they've been over torqued quite bit or rust has gotten into the threads. :grumpy:

 

[jbhasaboat]

Re: Rod cap movement

I actually feel pretty stupid now, it felt like I was putting hundreds of pounds of force into getting the rod cap bolts out. So I put a torque wench on it and I was only putting about 10 pounds of force. :facepalm: I turned it right to 30 and wahala they came right out. ( I did remember to loosen them in sequence, left side out a turn right side out a turn and so on) Now that I have the rod caps off the bearings look brand new so I don't think I will have a problem swapping cranks. I will also be replacing the lowering bearing with a new one and the main bearings with newish one from the other motor. Ill be sure to give you guys a report back on how this franken motor turns out, thanks for all the help!

 

[phillnjack2]

Re: Rod cap movement

you have it all stripped down so get the bores hones or a re-bore and do the job properly.

used crank,different used bearings, swapping over etc
man you are asking for about 5 hours if your lucky, and don't open it up full throttle or it will be less.

new pistons if they are scored and a re-bore...do it once and use all new bearings .

there is cheap and there is mean to the extreme.
this is a high performance outboard engine, not a briggs and Stratton lawn mower


phill

 

[jbhasaboat]

Re: Rod cap movement

After giving it a good look over I'm giving up on it, it has clearly been underwater; a place outboards shouldn't go. It needs a full rebuild and I cant afford to do that its around 800 just in parts and the exhaust manifold wont come off, like all the other Evinrude 3 cylinders I have encountered. So off to the corner of the shed it goes. Despite this ending badly I would like to thank everyone for helping me out with it anyway.

 

[schematic]

Re: Rod cap movement

this is a high performance outboard engine, not a briggs and Stratton lawn mower


phill

I once heard that Briggs & Stratton spent more on destructive engine testing than any other manufacturer!

Who knew!

 

[phillnjack2]

Re: Rod cap movement

yep that's right, and I bet they still did not use secondhand bearings ha ha


phill