Bad things happened today. 2001 35HP Johnson

[Bobbywolf]

2001 35HP Johnson (J35VL3SIE)

Well, I was cruising along wide open when there was a decent bang, and the engine died. I got it started again, but it sounded terrible, like rod knock.

I putted back to shore, and with it running, I pulled each plug wire off one at a time, and the top one had no effect on engine speed or sound. I pulled the head off back home, and there is carnage.

The top pison broke apart at the ring land, and pieces of ring and piston are embedded into the top of the piston, and marked up the head somewhat. I knew I was in for a cylinder bore, then oversize pistons at that point. Head looks salvageable. The bad cylinder is scored, but that should be fixed with an overbore.

Now my conundrum. I discovered the pistons are already oversized 0.030. Maybe my google-foo isn't so good, but I cannot find a 0.040 piston for this outboard. Am I totally hosed here? Is it possible to re-sleeve these?

Thanks for any assistance.

 

[racerone]

If in Canada contact ----evinrudeparts.ca------May offer you some help.

 

[Bobbywolf]

If in Canada contact ----evinrudeparts.ca------May offer you some help.

I've bought from them before. They are just a parts vendor and show the same 0.030 oversize piston only (OMC part). Sleeves are an aftermarket thing as well as possibly 0.040 pistons. I'm hoping someone had experience going bigger with aftermarket with these engines, or resleeving.

 

[racerone]

Sorry----They are not -----JUST----A parts vendor !!!!---You can find out what is at their address using say ---Google maps---- If you will.------They are a long established full service marina.----You may in fact be able to bore out the 25 HP version to fit standard 35 HP pistons !----First take yours apart to check condition of crankshaft and connecting rods.---I have much experience with these motors.

 

[gm280]

Well it could be worst. It could have popped a hole through the block.

If you can't find a 0.040" over, go re-sleeve route and piston and happy boating again...

Actually the way you posted the top cylinder issues, I'm not so sure a 0.040" over would clean up the damage. IDK not begin there and having a look-see.

And there are always after market pistons for most everything as well... Options are everywhere, it is just the money being the real issue...

 

[racerone]

Well----It might not be easy to find after market pistons for these 3 cylinder motors !!

 

[Bobbywolf]

Thanks everyone for the responses.

Update on the repair:

I found a company to sleeve and bore the cylinder in question. One crappy thing is these blocks are considered a blind cylinder, because the crank bearing journals overhang the cylinder by a little bit. VERY few companies around here can do a blind bore, but I had an older mercury done this way before at CVTech out of Quebec. I called them up and they can do the sleeve/bore job but their supply chain is screwed up due to recent events, so I would need to provide the piston/rings. Not a problem. I ordered pn: 5006700 (.030 piston and ring kit), a top end gasket kit and a OMC service manual for this motor for the reassembly.

Now the strange bit. The two pistons that are in perfect shape both show PN: 437282. These are 0.030 oversize pistons, to which I assumed the third damaged one was as well, so I didn't think any further, or even bother cleaning it.

I decided to clean up the bad piston anyways and hang it on the wall of shame I have (lol), and I found a different PN: 437219. Yup, standard bore. I whipped out my calipers and confirmed that the 2 good cylinders are over-sized, but the damaged cylinder is standard size. This seems very very strange to me, and I wonder if this is commonplace in the 2-stroke world?

Wouldn't the 2 different size piston/cylinders create different power, unbalancing the engine?

It works out better for me in the end since I simply need to bore the damaged cylinder, replace the piston/rings and I'm done. No sleeving required. Thoughts on the mismatched pistons?

 

[racerone]

So what is the percentage of difference between a standard bore and an o/s bore on your motor ?

 

[Bobbywolf]

I'm really not sure what you are getting at here, but I went ahead and figured it out. This standard 35hp 3cyl motor is 565cc's. Divide by 3 and we get 188.333cc per cylinder. Stock pistons are 63.5mm in diameter (2.5"), so that gives a stroke length of 59.5mm.

Using the new diameter of 64.262mm (2.530") gives us a cylinder volume of 193.1cc

This means that the oversized bore cylinders are 2.5% greater in volume than the standard bore. I would call that significant, but again, that is why I asked.

Is this commonplace to mix and match? If I had to bore out 1 cylinder, I would always do them all. Maybe I shouldn't be.

 

[racerone]

Replacing one piston is common on outboards.----Remember that compression does NOT start at the bottom of the stroke.----Compression starts once exhaust ports are closed off.

 

[Bobbywolf]

Replacing one piston is common on outboards.----Remember that compression does NOT start at the bottom of the stroke.----Compression starts once exhaust ports are closed off.

That is a good point, and I wonder if the cylinder volume published (cc's) is calculated from when the piston closes off the ports, or the entire stroke volume. I would guess the latter for marketing shenanigans.

Anyways, I have a long wait for parts to arrive before I can even send the block away. I will update this post, but it may be awhile. Luckily I have all winter to get this thing running in tip top shape again.

 

[Bobbywolf]

Pictures for posterity and those interested. My best guess is that somehow the ring caught on the exhaust port, causing things to self destruct. Truthfully it could be any number of things to cause this.

 

[Bobbywolf]

I figured I would update this. I forgot all about this thread, lol.

1 cylinder bored and honed, the other 2 left completely alone. Reassembled with 1 new cylinder and the thing worked beautifully. I still do not know what caused it to self destruct, but I have read that the 3cyl 25's and 35's were known for doing it.

Boat and motor are since sold, and I have moved on. (Edit - From THAT boat. I always have something to keep me on the water.) Story complete.

 

[Faztbullet]

Ring pin migration is reason it failed