1981 35 horse Johnson worth rebuilding?

[Badburn]

I have a J35ECIG with a small hole in the crankcase. Looks like the connecting rod got loose, or something got in between the rod and crankcase wall. Anyhow, it was running decent before this happened. Im wondering if anyone knows what years and or HP use the same crankcase, or maybe some advise to help me decide if it's worth rebuilding.

 

[Badburn]

Re: 1981 35 horse Johnson worth rebuilding?

wow, nothing?
ok, more specific question-
From reading other posts, it appears that 1976-1988 - 20-35 hp johnson all use the same powerhead, with different carbs and intakes. Can anyone confirm this?

 

[jasper60103]

Re: 1981 35 horse Johnson worth rebuilding?

I have an '81 25hp and it does share the same block. I'm thinking a '81 35hp is probably worth around $600-800 around my neck of the woods. Guess it depends on how much the repair would cost?

edit: my estimate is based off craigslist

 

[Badburn]

Re: 1981 35 horse Johnson worth rebuilding?

Looks like I'm gonna give it a shot. I found an 81 powerhead crankcase on ebay. This will be my first 2 stroke rebuild, does anyone know if you can regrind the crankshaft and or buy oversized bearings? I don't remember seeing an option for different bearings on the rebuild kits I've looked at.

 

[tx1961whaler]

Re: 1981 35 horse Johnson worth rebuilding?

Anything is possible, given enough time and $$. The crank can be repaired.
Once you get it apart, post pics.
An OEM manual would be most helpful at this point, if you don't already have one.
Look at it this way, a new 35 hp motor will cost you about $4,000.......

 

[Badburn]

Re: 1981 35 horse Johnson worth rebuilding?

Finally got around to this project, Found the problem. I already have a new block. At this time I need to find a good place to buy a rebuild kit, and one connecting rod. Any hot tips?? Found a local guy that can bore it for me. The only other thing I'm not clear on is what kind of sealer to use on the crankcase and gaskets. My manual just gives omc part numbers for the various sealers.

Old Block

 

[1946Zephyr]

Re: 1981 35 horse Johnson worth rebuilding?

You bought a block that needed to be bored? So sorry. I myself would have searched for one that was usable and just needed honing. One should have been obtainable. That way, you'll only need to shop for pistons and rings and save a bundle. That piston looks pretty "ouched" What in the world could have caused that?

 

[jbjennings]

Re: 1981 35 horse Johnson worth rebuilding?

I agree with Zephyr.... A GOOD used parts motor or powerhead would have been far cheaper. Too many of those out there to put all the dough into rebuilding a bad powerhead.
JMO,
JBJ

 

[Badburn]

Re: 1981 35 horse Johnson worth rebuilding?

Thanks for the input guys. Your comments bring me back to why I posted this thread back in August(see title). Anyway, I'm not positive that the new block has to be bored, I guess that will be decided soon. I don't have bore mic's to check it, but it looks decent.

New Block

 

[jbjennings]

Re: 1981 35 horse Johnson worth rebuilding?

I suspect since one of the water jacket diverting thingys is melted out or missing, that your used block had gotten hot at one time. If there are any grooves or scratches in the cylinder walls, it'll probably need boring, which will require oversize pistons and rings (probably $250 in parts just for that), plus other stuff. I'll bet you wind up with $750 in the block after machining, parts, etc. Then you'd have a like-new powerhead on an old lower unit. I'd still keep looking for a good used block that has good compression. A used motor in good shape could probably be found cheaper than you can rebuild yours the right way.
If you wanted to get by cheap, you might hone your block if it looks o.k., find a new used piston, rod, and crank assembly (I've bought 'em before on ebay cheap), and use new rings. No telling how long it would last, according to the clearances and if the bores are out of round. Don't forget to check the head for warpage.
Good luck either way. You'd have to count the fun factor of rebuilding it yourself for at least a couple of hundred.j
JBJ

 

[jbjennings]

Re: 1981 35 horse Johnson worth rebuilding?

Actually, this might make rebuilding worth it, if your crank is good:

http://cgi.ebay.com/ebaymotors/POWE...2238505QQptZBoatQ5fPartsQ5fAccessoriesQ5fGear

 

[Badburn]

Re: 1981 35 horse Johnson worth rebuilding?

Nice find JB. I was actually looking at that on ebay lastnight. I have no reason to believe that the crank is bad. All the bearings look good. I'm off to the machine shop today to figure out if the rod is hurt, and what condition the new cylinders are in. Initial measuring tells me that it's a stock bore at 3.000 inches. The small end of the rod looks remarkably good and checks out ok with the cheap-o dial caliper I have in my garage. I find it hard to believe that it could be "ok" after seeing the condition of the wrist pin that came out of there. We will see.

 

[Badburn]

Re: 1981 35 horse Johnson worth rebuilding?

Machine shop revealed a standard 3" bore that is .0045 out of round on one cylinder and .0025 in the other. I think the specs in my service manual say .003 is the maximum allowable. So it's getting bored to .020.

The small end of the rod was checked for roundness and taper from one side to the other. It checked out good, almost perfect, and it got the thumbs up from my machinist.

$40 a hole to bore it, and $15 to clean it seems like a good deal to me. I was ordering new pistons anyway, so for less than $100 I will get a fresh new perfect bore. Again, this is my first 2 stroke rebuild, so if anyone see's anything I'm missing here, let's hear it.

Found a rebuild kit on ebay, $240 for bearings gaskets pistons and seals.
http://cgi.ebay.com/ebaymotors/POWERHEAD-REBUILD-KIT-JOHNSON-EVINRUDE-20-35HP-81-04-_W0QQcmdZViewItemQQhashZitem439a578fa9QQitemZ290352238505QQptZBoatQ5fPartsQ5fAccessoriesQ5fGear

It's from a company called Tri State Marine, and he advertises a two year warranty. Almost seems too good to be true, but he has good feedback and I think I'm gonna go with it. I called the guy and he said that he manufactures some of the parts and that's why it's priced so well. So, now I wait for parts.........

 

[58rude]

Re: 1981 35 horse Johnson worth rebuilding?

Pistons will need the correct side clearance. I would hold off on the bore and hone until you mic the pistons. Any good machinist will know this, hope yours told you that. Not trying too say anything bad, just would hate for the guy too bore and hone it and bore be too big for the slug. Also make sure you check your ring gap in each bore. Good luck.

 

[Badburn]

Re: 1981 35 horse Johnson worth rebuilding?

Thanks 58rude, He did send me home untill I have pistons. I'm supposed to get the clearance specs from the piston manufacturer. There is nothing that I can find in the OMC service manual. Any input on that would be helpful.

I did find the ring end gap specs in the service manual. Can't remember what they were now, but I will check them.

On another note, I have a hairbrain idea. While doing my research here, I came across some info about porting the exhaust side of the cylinders. Basically it said to square the exhaust ports and raise them .050. Has anyone tried anything like this? I was told it would add a few HP on this model of engine.

This is the boat this motor goes on, I'm thinking a little extra power would be good.

 

[samo_ott]

Re: 1981 35 horse Johnson worth rebuilding?

Hey, nice boat. How fast does it go with the 35?

 

[Faztbullet]

Re: 1981 35 horse Johnson worth rebuilding?

I got the perfect motor for that boat...1975 short shaft 50 with nitro gearcase!!!!

 

[Badburn]

Re: 1981 35 horse Johnson worth rebuilding?

I got the perfect motor for that boat...1975 short shaft 50 with nitro gearcase!!!!

Pm me if youre serious. This boat only goes about 28 or so. I thought it would be faster when I got it, but now I'm thinking maybe the skirt has been broken off of that piston the whole time. I'm thinking that would nearly kill that cylinder totally because the length of the skirt is what times the intake and exhaust cycles. Anyhow, if this thing doesnt pick up 15 or 20 mph with a good powerhead, then I will be selling the motor and looking for a bigger one.

 

[Badburn]

Re: 1981 35 horse Johnson worth rebuilding?

Pistons will need the correct side clearance. I would hold off on the bore and hone until you mic the pistons. Any good machinist will know this, hope yours told you that. Not trying too say anything bad, just would hate for the guy too bore and hone it and bore be too big for the slug. Also make sure you check your ring gap in each bore. Good luck.

After ordering the parts today and talking with the guy about piston clearance, it sounds like I can go ahead and just bore the block. I ended up ordering .030 pistons because they were in stock. He tells me that they are cnc machined, so every one is exactly the same. The pistons are manufactured at 140 degrees and are cut round at that temperature. He says when they cool, they are no longer round, and if I try to measure them I will not get an accurate measurment. He says that they are designed to fit in a bore that is exactly 3.030.

Interesting, this goes against everything thay I know and have been told, but it sounds like it makes sense. Any thoughts?

 

[Faztbullet]

Re: 1981 35 horse Johnson worth rebuilding?

Check your Pm!!!!! ,,,,and you got to watch Mike, as the kit he sells is from WSM( I sell also) and he dont make anything in kit.