"0" Compression

[Brock O]

Hi Guys,

Firstly great forum! I've been reading for a few months but now have to ask a question or two. This my second boat and of more age than the first so have been doing all work myself using the manual and this forum for info.

Its a 1995 Johnson 115HP, 2 stroke model TLEOR, hopefully I'm adding this to the right section, I've been throwing parts at it for piece of mind as its been problematic since the rushed purchase, lack of maintenance in most cases it seems. Any way, after putting carby kits through and having the boat running sweat at WOT 5500rpm all problems seemed to be behind me, after settling back to idle and turning the motor off to see how the restart would be at temperature the problem occurred, it started with a rough idle and a max of 3500rpms from then on.

New plugs, leads and coils had previously been fitted but when pulling the plug on one cylinder the motor would not change note, the plug had came up black and oiled so my thoughts were the lead or coil, I would get a kick when pulling the coil end of the lead but nothing at the plug end, I can hear the clicking sound when refitting the lead but no change to the motor's performance, change of plug brought the same response. After performing a compression check today left side 109 & 109 right side 99 and ZERO, motor makes a totally different sound when checking this cylinder, now during the previous run at 5500 I herd no clunking or banging...excessive smoke or cooking smell. Even during the compression test with the motor hot, there's no signs of leaking at the gaskets, oil or fuel leaks to that cylinder....could broken or stuck ring's give an absolute zero reading ? or am I missing something. Compression kit was brand new, tried this a few times over a Few cylinders as I thought something must be wrong .

So your thoughts on the problem would be great.......I'm reading the mechanical section now in preparation of an overhaul, would it be wise to remove the cylinder head for inspection first before pulling the Power head off, and are there any trick's to pulling down this motor other than following the manual's procedures ?

Any thoughts greatly appreciated, I think I'm 12 hours ahead so will be late on reply's.

Brock

 

[steelespike]

Sure doesn't sound good. I can't speak specifically to this motor but it appears you need to look at the piston.
You could try looking through the plug hole with the piston down.Many motors it is suggested to remove the
exhaust cover and transport covers to view the sides of the piston.If your going to be doing a rebuild you will need a factory repair manual.
Others better acquainted with these motors may be able to help with the details. I believe Iboats has reprint factory manuals.

 

[rickryder]

I would rent /borrow a bore-a-scope from your auto store and have a look at your piston....might have a hole burned in it or your rings are done

 

[Brock O]

Cheers Guys

I've only eye-balled down the plug hole at this stage and I can see the piston top as such...not a big hole as one would think. Ill have a closer look tomorrow with torch, might just pull the head in any case to get a few photo's.......

Manual is sorted and ready to go.

 

[racerone]

Very common to break piston rings on these motors.-----Picked up a 1995 model myself at a dealer with same pronlems.---Cosmetically it looks to be 2 yers old , but mechanically the dealer could not repair it at a reasonable cost.------Very , very common failure.

 

[gm280]

After reading the comments, I hope it is piston ring issues and not a head cracked over that cylinder. But if it were a cracked head, you would probably hear the compression leaking as the piston was coming up. so hopefully that rules that out. The fact that you had zero compression is suspect. Even broken rings you should have something....even if it was a really low reading. I'll certainly be watching this for the reason myself!

 

[racerone]

Well, a cracked head would be CHEAP easy fix !!

 

[emdsapmgr]

Unlikely a cracked head. Likely the ringset (usually the top ring) let go on the low compression cyl, as racerone noted. When it goes, it breaks into pics and the pcs are broken into smaller bits by the piston compressing the loose ring between the crown and the head face. You'll wind up with either low compression of no compression on that cyl. Pull the head off that side and visually inspect it. Unless there was serious damage done to the piston walls, you can hone/install a new piston and 4 new ringsets after teardown. The factory would suggest you also replace the dented head-my preference, but others will run it- dented. (you run the old head at your risk.) You'll need to know the reason for the failure, prior to running the overhauled block. Was it a carb main jet that was restricted, or an overheat on that cyl due to stuck thermostat and/or bad pressure relief valve in the thermostat housing, or a misplaced water diverter in the block? Any can cause a lean condition, leading to an overheated/cracked top ring. When this happens, you may not get a hot horn warning.

 

[racerone]

All kinds of cylinder heads on E-Bay at $40 and up and that would be the CHEAP fix.----I get blisters on my fingers explaining how common this failure of broken rings is.

 

[Bosunsmate]

Pull the bypass cover for that cylinder and inspect the rings for sprinyness.
392754 — COVER, BYPASS look that part up if you arent sure what it is, just undo the four bolts holding it on.
If they are ok, remove the head and inspect the gasket, but either way you will be removing that head anyway

 

[Bosunsmate]

You can rebuild these for a few hundred bucks if you know what you are doing. If the cylinder needs reboring ring a machine shop, i was in fremantle last year, from what i saw there would be no shortage of such shops there

 

[Big Fish Billy]

Sounds like a hole through the piston to me, time will tell.......

 

[Brock O]

Morning..late start due to a few drinks to help me sleep. Thanks heaps for the reply's, ill pull the head today and take some photo's, ill check the inspection hatch on the diagram and have a closer look today when I get to the boat.

Emdsapmgr, previous problems were alarm issues, sometimes a continues beep and a couple at intervals, and hard starting or no start at all once hot! I replaced the water pump and thermostats, the thermostats were almost non existent. but the alarm problem's did go away, had plenty of exposed wires through out as well including a bad positive lead from the battery which was orange and almost broken through.Its been a constant battle. I guess finding the cause is the biggest thing here, rebuild is a pain but if it will serve me well after then all good, would hate for it to happen again, would rather go buy a decent second hand four stroke. Thanks again, will get back with some photo's once the head off.

Brock

 

[Brock O]

Well I'm sitting down having another Bourbon!!

Did some one say BROKEN rings was a conmen failure! Well let me say firstly, the fact I didn't of all thing's perform a basic compression test is my own fault, don't know how many times I've read this.....To tell the truth the motor did sound all right when I purchased and it was running ok, so the major damage may have only just occurred but I think I could have avoided it had I done a test before purchase.

Any way pictures attached, both cylinders have no top ring left at all even though one was reading 99 the other zero, bottom bore at a glance is past the 30 thou mark, top cylinder bore seems ok with the finger nail. really not sure were to go with this now! I'm surprised it still starts and idle's...were would the rings have gone??

I guess the ring failure would come down to the VRO ? its seems oil'y enough! I'm guessing the previous alarms and rough running was the motor destroying itself. What would be the most likely cause of this ?

 

[Chinewalker]

Ring failure had nothing to do with the VRO. Could be related to heat buildup due to lugging. These crossflow V4s really need to spin up to maintain proper temps. If they aren't capable of peaking a tad over 5500 RPM at wide open, then they're being lugged. Not saying you have to run it that hard, but they need to be capable of it. Too much prop and it's akin to driving up hill in overdrive, while towing a trailer and bucking a headwind.

 

[emdsapmgr]

I would not immediately blame the VRO. They are usually pretty reliable. You need to check the higher priority failure items first. As you said, it appears oily. If you had a VRO failure, all 4 cyls would have cooked, not just two on one side. Rings fail due to overheating. You've got an overheat failure on one side of the block. Some things to check first: 1. Since the problem occurs on one side of the engine, it's unlikely the carbs, as they also feed the two cyls on the other bank. The rubber water diverters in the block (one to a cylinder) must be positioned correctly to divert water flow around both cyls. If they get restricted, they restrict water flow. (See picture for normal diverter placement-the center one is correct, the one on the right is misplaced and can cause an overheat.) It does not matter how much oil you get if the ring runs hot from lack of coolant. 2. You've got debris inside the thermostat housing-lots. What you see inside that housing may well be inside the block-restricting water flow around the cylinders. You've got the heads off now-compare the appearance of your block with the one in the attached pic. Note the difference in cleanliness of the cooling passages between the two blocks 3. Pull the head covers off both heads and see what the cooling passages look like inside-they may also be restricted. You can clean them. If they are, you may also need to pull the rectifier/regulator off the top of the block and make a visual inspection of the cooling gallery below for debris. 4. The bottom right pic shows cylinder wall scuffing. Aluminum from the piston has delaminated and stuck to the cylinder as it ran hot. It's been doing that for some time to look like that. You'll need to clean that aluminum transfer off the cyl walls. Use a few drops of muratic acid to dissolve the aluminum that has transferred to the cyl liner wall. Once cleaned up, check the bore to see if there are vertical gouge marks on the liner wall at all. If so, you may have to overbore that cylinder and go with an oversize piston on that one hole. Remove the prop so you can look down the exhaust opening in the lower unit. You may fine bits of broken rings deep inside that cavity. 5. Due to the failure mode, it's not likely the carbs, but as insurance, I'd pull all for main jets out and check them for any debris which would cause a fuel restriction (and lean condition) which could also lead to overheating. Esp pay attention to the two mains that feed the bad cyls.

 

[Brock O]

WOW..there's a big difference in the water galley between the too, looking at my old thermostats its easy to tell why, they were a prick to replace, needed two butter knives and a extra set of hands to get the bolts started. It would take some work to get this ready for rebuild, then to find out the wall is over the 30 thou then what ? haven't checked what's available in this motor regarding piston size. I'm leaning more towards ditching it!! Just found another motor...Johnson 2003 115hp 2 stroke for $3500.

looking at the photo's and the problem, cost for gaskets and parts to get this back running ? if I was going to do it! it would be bearing's big and small through out, new pistons and rings for all four cylinders plus machining, All would have to purchased from the states as all boat shops wear balaclava's here!! If any one can give a price for parts for the above...would be most appreciative!

Brock

 

[racerone]

All you have to do is draw a picture of the 2 rings in the groove.-You will then note that as the bottom ring starts to wear the side clearance does NOT increase.---Then see what happens to the side clearance on the ring with the big chamfer.----As it wears the side clearance INCREASES.-The rings starts to bounce around in the groove and breaks.----No mystery to me !

 

[Brock O]

What are you saying Race?, this is more due to time and wear rather than over heating...its 1995 and I know the 2 previous owners and the hours wouldn't stretch 800 or 900 hundred. **** poor for a motor if you ask me, id think this is due to a heat issue....lack of flushing and maintenance of thermostats.

My issue..

 

[racerone]

I have about 20 motors on hand with broken ringsn in them ( for parts / rebuild ) so if I have 20 or more it is a common failure !!!!