Burning piston on cylinder 4

[rdeyoe]

Re: Burning piston on cylinder 4

Thanks emdsapmgr. Are all the jets for JE carbs pretty standard? Where is the best place to get them? If I search for 68c or 69c orifice, I get lots of hits for other years but not these carbs.

@Faztbullet: I didn't get the chance to check the WOT timing (forgot the timing light at home), but I did find a procedure for doing the setting out of the water here. Checking it at full crank with plugs out and setting it back 4 degrees (24*, i guess), so I'm going to give that one a try. The timer base has already been replaced on this one, and all the plugs seem to be firing hot and correctly. Hopefully I just have the timing to far advanced for WOT....that seems to be where the issue occurred.

 

[boobie]

Re: Burning piston on cylinder 4

Geeez, I thought I mentioned timing in post # 2. O'well.

 

[stackz]

Re: Burning piston on cylinder 4

I'm absolutely loving this thread. nothing to comment other than the large amounts of engine theory being tossed around. very rare!

 

[boobie]

Re: Burning piston on cylinder 4

No! It's not theory! There's a lot of experienced techs on here just trying to help someone out with a problem who have experienced the prob themselves.

 

[Haffiman]

Re: Burning piston on cylinder 4

If I have gotten it right, this is at least the third rebuild of this block!
Something out of the ordinary is causing this, and I do not believe the real cause for previous break downs have been found.
Throw away the block, or do some out of the ordinary to eliminate any possible cause for the break downs.
Such a major damage after such a short running time after last rebuild - on an engine working with (more than?)full power and perfect idle???
Time to think beyond the standard A1 solutions and causes.

 

[rdeyoe]

Re: Burning piston on cylinder 4

@stackz: Yeah! I'm loving all the information coming out. I've poured over the whole site for conditions like mine, and have gained so much knowledge. One of the reasons I ordered the parts I need from this site, just trying to give back a little. Plus the prices were right!

@boobie: Going to reassemble today. I will definitely check every timing piece, and timing at WOT (static, just cranking on muffs) just for you...and 'cause I like your username!

@Haffiman: I see what you're saying. I still have the heads off (just got the gaskets this week). I will be looking very closely at the block and liners and see if I can see any cracks. I'm going to check flatness of the heads also, maybe they're seeping. This is actually only the second time I've had it apart. Someone had put the .030 pistons in before I bought the boat. But the ring pins migrated out in two cylinders (ran it pretty hard a whole season), causing the rings to explode...hence the reason for me to take it apart and replace four pistons.

Also on list: Pull carb float bowls and all jets. Check sizes and clogs (i hope i find a golf ball stuck in #4 high speed!). Check fuel pump diaphragm and poppet valves for deterioration. Check for double fire conditions on all cylinders. Make sure that exhaust cover is flat and non-porous and that gasket is sealing.

Hope to get some running time today or tomorrow. I'll keep y'all posted, and much appreciation to all of you!

 

[Haffiman]

Re: Burning piston on cylinder 4

Check your spark plugs frequently. If you see a 'white' one STOP!!!

 

[Faztbullet]

Re: Burning piston on cylinder 4

But the ring pins migrated out in two cylinders (ran it pretty hard a whole season), causing the rings to explode.

Never seen this on a crossflow engine but anything can happen... pins migrate due to cooling problems. If it was old style piston with roll pins I can see it. Most of the time rings roll due to carbon build up in ring lands from cheap oil,cheap fuel and engine running to cold...

 

[rdeyoe]

Re: Burning piston on cylinder 4

Thanks fazt. I believe they were roll pins, from what I could tell of what was left of them.

We put the heads back on, with the old gaskets. Put the exhaust manifold and bubble back on. Made a block off plate for the water passages on the bottom and put a 3/8" hose in the water pump feed. Put a vacuum on the pee tube and sucked water into the engine through the 3/8" hose. Worked quite well. Then we blocked off the vacuum line at the pee tube and put 30 psi into the water pump inlet and clamped it off. Couldn't heat the whole engine to operating temp, but I am seeing a leak, through the exhaust outlet, between the exhaust filler blocks. Also have a gasket leak between the exhaust manifold and the bubble back (minor). Going to let the pressure leak off and disassemble the heads and exhaust, see if we have anything in the cylinder. The piston is below the intake ports and it seems to be dry right now. Will post results and pics....

 

[rdeyoe]

Re: Burning piston on cylinder 4

Evenin' gentlemen. Got the "redneck pressure" test done. Cylinders were dry, and ports too. There was a good drip at the exhaust manifold into the midsection junction area. Tried to get some pics of it, but kind of hard in that area. Got the heads and exhaust back off, cylinders were dry, just pooling in the center vee area of the exhaust side. Pretty satisfied with the water test, other than external leaking (had to make new gasket, and resealed with thin films of high temp rtv on the ex. manifold and bubble back) it looks ok.

Moved on to the carbs. Pulled the lower (3-4) carb. Yanked off the float bowl, nice and clean, no sediment. Pulled the jet plugs, could see light straight through the high speed jets....looks clear. Pulled the jets, high speed and idle. Could see light through all of them so good and clear yes?....NO!!! Looked in the inner edge of the #4 high speed jet and there was my golf ball !!! There was something laying against flat against the wall of the inflow side of the jet.





It was thin, rubbery. I pulled it between fingernails and it snapped back to shape. May have been a piece of the short fuel line from the carb inlet to the carb tee...on the out flow of the fuel pump. None of the rest of the jets had anything in them. Used cleaner and compressed air in all passages and jets. Replaced both carb feed lines (about the only fuel lines I hadn't replaced on the whole boat so far...almost out of the 25' line I bought). Need to change out the one from the quick disconnect to the fuel pump also...the rest are all changed. I also took apart the pump to check diaphragm, still new.

I'm pretty sure that this must've been it. It was a flat piece laying against the jet wall, on the inflow side of the jet. I'll bet going to WOT sucked it shut like a trap door. It was almost exactly the diameter of the jet inflow. Got the motor together and mounted tonight. Going to strap the electronics and harnesses on tomorrow and hopefully get back to my break in.

Finally, something saying "I'm broken". Strangely, it was kind of a relief to see that piece of trash in there.....

 

[Haffiman]

Re: Burning piston on cylinder 4

If running a fixed tank installation, drop the 'quick connect' and put the hose straight onto the pump or inline-filter if you are using that.
Will be waiting for the test results, at least after 10-20 hrs break in.

 

[sschefer]

Re: Burning piston on cylinder 4

Check the positioning of the water deflector around that specific cylinder. Possible it is out of positon. If one of those 4 gets out of position, it will cause that cyl to run hot (same as running lean) and can cause the results you see. Since the head still receives cooling water, you usually won't hear a hot horn-signalling of the the overheat.

That's the ticket, the symptoms are typical of a two stroke overheated cylinder.

 

[emdsapmgr]

Re: Burning piston on cylinder 4

Nice find! A good time to replace any original fuel hoses that may still be on that engine. Ethanol in the fuel will break those 1981 hoses down.

 

[rdeyoe]

Re: Burning piston on cylinder 4

River didn't want to cooperate today. Weather was nice, but too windy, and water level in the Cumberland river is low. Didn't look like a good day to try it (got some more fishing in though! . We did get some initial start(s) on the muffs in the yard. Took a few times to get her going, and when it started, it sounded like it was lugging. Port head stayed cold....no fire on that side. Wiggled some connectors and she fired on all four, unexpectedly. Cleaned the faulty connection and put some dielectric grease in it. Checked the idle timing, got it bang on. Also did the cranking WOT timing in the yard. Looks good, maybe a half degree on the safe side (23.5* just cranking at WOT). Idle is at 900 on the muffs. Head temps...upper cyls both sides about 126, lower cyls about 134. Thermostat housing around 124. Let her run about 20 minutes. Pulled plugs, all look about the same (probably can't tell anything from the plugs until we get some water time), they were all at least wet. The .064 piston seemed be be drier / cleaner than the other three, might need to put jets in that one?...larger idle jet? Looked through plug holes at pistons. All looked "moist", ...number 4 is still silver and shiny, but did have oil on it (as I would expect, problem wasn't at idle). Checked compression on number 4 and she's back up to ~120. Water flow appears to be good. Pee stream is very strong, cool. Have to replace some clamps on the thermostat hoses, dripping a little. Outlet water at lower unit is cold, except for thermostat openings, just luke warm there.

Looking forward to running her on the water....maybe next weekend will be nice. Not going to know anything until we get some hours on her. The starting and idle is pretty sweet though. While she's been a pain in the @$$, I love that two cycle sound of a Big Ol' Johnson. Hopefully I can keep it going now...

Thanks haffiman, emdsapmgr, boobie, faztbullet. You've given me great insight and knowledge. What is most invaluable is knowing (between this rebuild and the lower unit, fuel pump and lines, starter and solenoid and bendix, etc. etc. etc.) is that now I know the motor and boat inside and out. If it makes a strange noise, I'll know where to go, if it loses fire on a plug, I have a better idea....that kind of thing. Captain of a vessel is supposed to know everything about it, and i'm getting closer. I'll keep y'all posted on the progress....appreciate ya!

 

[rdeyoe]

Re: Burning piston on cylinder 4

Weather we nice enough this weekend. Sorry for the long stories, but some may need it:

Got her down to the local marina. Popped easy after two cranks, a little primer jiggling and a thirty second warm up (on the throttle, i don't have a warm up lever), she was idling at neutral at 700 or so...a bit low i figured, but in reverse it wasn't much different...600-650. Pulled from the ramp smooth, idle only. Went a couple of circles while my lady was coming back from parking the truck....and headed out.

By the Mar-fab break instructions, we did the first ten minutes running at 1500, with momentary jumps up (less than) 2500 and back (we used a cell phone to time all these runs). Next 30 minutes were mostly at 2000, up to 3800 (mar-fab says "to plane", but my craft won't plane at less) and hold on plane (we stayed at 3500, cruising), and back down, several times over the 30 minutes. Checked temps and timing during these runs, as max timing seems to hit about 3000 (did the driveway WOT timing, and my WOT timing at 3000 is at 24* or so....running on the water was no different apparently). Temps at idle were around 130, at 3000 went down to 98. Stopped for a bit after the 30 mins to check the plugs. All looked similar, with some minor aluminum slivering, and some carbon....not serious, just slightly shiny in sunlight.

Started back up, and next phase was to go "WOT without prolonged periods" and returning to idle for cool off for 30 minutes. So, with our timer, I would run up to 3500 (plane) and then hammer it to WOT, with my darlin running the clock. We'd run 5400 rpm for 30 seconds (i think she was shutting me down about 20, but i'm not going to fight her over it!), and return to idle for 1 minute. Did LOTS of these, until we were in the next county. We anchored off and did some fishing for a couple of hours...enough work for now. Did a plug check again. All looked moist, not soaked, clean. Silvering was much less this time around.

Started getting dark and cool. Weighed anchor and headed back. We ran it back for about an hour mostly around 4500, with a few runs down to 2000-2500....and a couple of runs at 5400. Made sure that we're varying the rpms a lot. Got the truck down the ramp while my girl kept the boat at the dock, tied and off. Cranked her right up and she was very docile on to the trailer....response was good, a bit of blubbering at idle, might crank it up a tad.

Flushed at home. Great cold start...one crank (on a JOHNSON?!). Parked her and checked plugs again. Number one looked a little dry, carboned. The others matched,...no silvering this time. Looked at pistons through holes. Number one is a bit dry, only on the exhaust side, intake side looked moist....all others were barely wet, and slightly carboning. The number 4 wasn't any different than any of the others. And no milky residue (water intrusion, as far as I can tell).

All in all, a WONDERFUL day. Weather was great, river was a sheet of glass, motor popped off every bump and ran very strong (jumping out of the water again). Figure we did about 3 hours on a rebuild (we're starting over with the new piston), still have 7 hours to go for a good break-in. Covered about 20 miles on the river. Seems like a win so far.

I have new jets coming, one size (68) larger for the .040" over pistons, two sizes (69) for the .064" over size one. After this weekend, not sure I need them, but a little more fuel/oil might make it last longer. I've been kinda frustrated with this outboard, but after this weekend, I may be able to give it a (few) more chances...or maybe it's giving me some....

 

[Haffiman]

Re: Burning piston on cylinder 4

Sounds good, let us hope it stays that way!!
Hopefully the wife is as happy as the engine.

 

[Faztbullet]

Re: Burning piston on cylinder 4

Also did the cranking WOT timing in the yard. Looks good, maybe a half degree on the safe side (23.5* just cranking at WOT).

Did you do this the Joe Reeves way ??? OMC motor timing notbe set like a Merc unless you do it like Joe.s post as they gain timing with rpm....

 

[rdeyoe]

Re: Burning piston on cylinder 4

@Faztbullet: Yeah, that was the post here that I caught. Can't find it again now, believe it's a sticky someplace. We only did a few runs of about a minute or two at full open rpms, 5400 or so. Most of the day was around 4500. The timing is set to the safer side of advance. After a couple more hours of break-in, I'll check it at full WOT. Keeping the throttle a bit lower than full for now...

@Haff: I'm going to do my best to keep it this way. And yeah, she's loving the power and smoothness now. Even more considering she's done a lot of the work along with me. Good feeling when you know what's in there and get to hear it run like this!