RickK's 115 rebuild

[RickK]

Hi all,
My 170's engine stopped working when I was out with my grand daughter.  She had just finished "driving the boat" for an hour or so at idle through a idle zone that is awesome  visually. We headed back intot he bay and it started sputtering and quit - simple as that - no noise or anything, just quit running.  it wouldn't start again.  I figured my grand daughter would freak out a little but ended up she was an old pro at this - her daddy's boat had to be towed in when she was on it.
Anyway, called SeaTow and was towed in - it was about 6 miles I think.  He said it would have been 3-400 dollars if we didn't have the insurance 
Dropped it off with my mechanic on the way home.  He said that one piston was loose, meaning that it could be moved 3/8" in and out of the cylinder.  Otherwise the cylinder looked ok.  I decided to rebuild it myself and I brought it to my buddy's house and we started tearing it down - my first time BTW.

We started the disassembly and the first thing that is of concern to me is how eaten away the bottom of the powerhead is:


Exposed the crank


The 2nd rod from the right is the one connected to the piston that is damaged. When I looked at the crank cover there was a gouge in the cover that lines up with this cap - don't have a pic of it but we don't think it'll affect anything.  Will get a pic of it today.


The cap bolts were actually loose, while all the others were still torqued so we knew there was trouble.  We hand cranked the engine and watched this rod and then when I pushed back in on the piston there was evidence that there was NO bearings under the cap!


You can see where the lack of bearings wore a groove in the crank - so we think the crank is toast.


This is one of the pistons, not sure it is the one with the missing bearings, but scored none the less. A little blurry.


Some scoring on the sleeve of one of the cylinders and I don't think it was the one without bearings, but above it.




Here is a pic of the block - the damaged piston was the 2nd up from the bottom.  The color of the block seemed to be more "brown" in the lower 2 cylinders vs the upper. Already took the block to a machine shop and they started boiling it yesterday.


I was conferring with Fitz and sending him pics during the discovery (these pics).  He thought possibly water intrusion and based on the condition of the bearings, I'm sure that something washed the lube off them. I decided after talking to Fitz that maybe I should find another block since we couldn't be sure what caused the problem.
I found a short block and bought it.
Everything is back together but the carbs, which I gave to my mechanic to rebuild.  I have them back now but have been pre-occupied with the rebuild of the 170 to finish the engine.  Hopefully next week I'll take an hour and install the carbs.  Will still be a while before I can test the engine.

[gran398]

Excellent

[seabob4]

Someday Rick, I'm going to attempt the same thing you're doing.  My deal is electrical, you know that.  But getting inside a motor and understanding what it is I see?  Want to do it...

Keep the pics coming!

[GoneFission]

Hard to believe someone would put the bearing race in without the bearings - that's just weird...

Did you check in the bottom of the block to see if maybe the cap was loose and the bearing pins came out and dropped down?  

Anyway - crank, rod, etc. is in order - good idea to pick up a new block and save some trouble...

[RickK]

We didn't see anything floating around that looked like metal.  It's too bad the crank needed to be replaced, that added a chunk of change to the equation.  When I bought the short block the "core" that needed to be turned in was a good serviceable block that was still able to be bored.  The factory bore is 3.6: The bore in this block was 3.612" and the max it can be bored is 3.63" - so the block was still within the core requirement.  Also I needed a good crank and 4 connecting rods with caps.  I had to pay for a reman'd crank and one rod/cap, so it bumped up the costs about $600.

[Aswaff400]

love a good engine tear down.  

in toyr 3rd pic, rust on the cap/rod, tell tale sign water was finding its way in there... not finding any chunks, its a 2 stroke, it will find its way out of the motor.

when my old 302 melted a piston, a large chunk of the #8 piston was missing, pulled the muffler from that bank, shook it, could hear it bouncing around in there!  

[fitz73222]

The main problem with most of todays outboards is accessability to the internal components like exhaust plates. In the 80`s and 90's alot of OEM's changed casting techniques from the standard sandcast method to lost foam. Traditional sandcast methods forced the OEM's to cast less intricate components and forced more assembly and machining of the block components. That gave you access to transfer ports (intake side) and exhaust plates (exhaust side). Many outboards die from exhaust plate erosion and injest cooling water through the exhaust ports. In the old days you could remove, inspect and replace the exhaust plate and save the powerhead. Because of lost foam casting, the powerheads are cast with much more intricacy including the exhaust plates and are no longer a servicable component. This lowered manufacturing costs dramatically by reducing secondary machining, gaskets and labor costs. Great for the OEM's, bad for us down the road. So the rub today is that if your engine starts to injest water and it didn't come through the fuel system or a bad headgasket, chances are the block is leaking internally and scrap! Rick's block had all the signs of internal leakage and heavily corroded. Really the only thing you can do is keep it flushed at every opportunity to extend the block life.

[Georgie]

I'd say it's pretty safe to assume that the "beautiful" groove in your crank explains the play you noticed in your piston stroke.  Aren't those actually the frozen and melted/eroded bearings left in the race?

So you're already done re-assembling the replacement block (minus the carbs)?  That was pretty quick!    How/where did you find the replacement so quickly?  New or used?

[wingtime]

The remains of the roller bearings are still in the what is left of the race...  they are just flat now!  The rod is rusty where the cap is due to the high heat of the bearings....   I have seen that before even on trailer hubs.  The thing was hot enough to cause the steel to start to oxidize hence the rust and discoloration.  That rod is probably no good anyways due to the heat damage. You can also see the burned oil further up the rod.  There is no oil or carbon on the rusty area since it was hot enough to burn it all off....   probably a roller bearing started to go or became stuck....  things started to heat up and the rest of them stuck and everything just started wear out quick once that happened...  All that didn't take long to happen...  probably while you were idling along.... if it happened at high speed it would have self destructed pretty quick!

[John Jones]

Nice post Rick.  I'm amazed you did not hear the rod knocking even at idle.  A friends Merc went out the same way but it sounded like someone was inside the cowling with a hammer.
Good luck with the rest of the rebuild.

[RickK]

Georgie - I found the short block reman'd in Tampa.

I know that GF saw the remains of the bearings in the cap and figured he was posting in jest.  I think that the engine took on water but I'm no expert, so I have to trust people I talk to. Either way, the corrosion on the bottom of the powerhead woried me (the reman'd one I got was actually worse   ).
One thing I learned was how little there is inside these things. Nothing like a 4 stroke i.e. car engine.  The only tricky thing about the reassembly (which I didn't do since I bought a reman'd) from what I read and was told was that the alignment of the rod cap was pretty critical.  You could buy a $500 alignment tool (which some reviews said made it worse) or you could do the pencil line or fingernail check. Other than that it seemed like a piece of cake. Nothing I wouldn't tackle again if necessary (knocking on wood).

JJ - it just died.  We were cruising about 25 and it just did like a self-protection idle down and then died. No loud anything (except the engine in general)

[seabob4]

JJ - it just died.  We were cruising about 25 and it just did like a self-protection idle down and then died. No loud anything (except the engine in general)

Rick,
When I was in college, I had a '72 Merc Marquis with a 428...used to leak oil.  Coming back from University of Iowa one weekend, booking along I-80 at about 80 MPH, heard a dull thud (one of those "what was that? moments), then sheer silence.  No warning, no knock, no "all hell's gonna break loose any second now" revelations, just silence...

When she got back to Champaign, had a 2" hole in the side of the block where a rod decided to exit.  Traded the car for the towing bill...