2006 Merc 115hp 4-stroke won't turn completely over?

[rebmo]

I have a 2006 Merc 115 hp 4-stroke on a Lund 1700 Explorer with 40hrs on it that died and now won't start? First, this motor is maintained regularly with oil changes each season and lube, water pump, etc.. It always performed flawlessly. Yes it's had light use and that could be a concern too, but it has been well cared for.

3 weeks ago we pulled it out of storage, put the muffs on and started it up. If fired right away and idled fine. I put it in forward, then reverse, with a little throttle all fine, back to neutral and shut it off all in about 10 minutes. So all looked good. Oil clean from last year end of season change. fuel with preservatives (mercury) from last season. Took to the launch nearby and put in the water and fired right up so let idle, parked the truck, came back and my son hit the tether switch backing away from the captain seat. We reset the tether switch and tried to start and it just cranked. Tried a few times for only a few seconds then let it rest. Tried to start again after about 10 minutes and it sputtered, but didn't fire up. Gave it another rest and tried a couple more times and the battery got too low. So I pulled one of the full charged trolling batteries and hooked it up and all I got was a click. Took the original battery back home, charged it, came back and it just clicked. At this point I just trolled it back on the trailer and took it home.

I then bought a new battery since the one I had was 4 years old. The new battery made no difference. The fuse was good. I checked out the wiring and found the 12v breaker on the hot side of the battery was open so I replaced that, not luck just clicking with a turn of the key. With the hood off measured the voltage at the starter. Perfect ground and 12.8V at the battery and solenoid. I then measured the voltage trying to start and it dropped to 8v. Now I was sure the starter was bad. I looked over the starter and the top bushing housing had a crack. So now sure it was the starter, got a new one to replace it. The Merc Dealer ordered one for about 350 and it came and sure enough they ordered the wrong one. So they actually looked it up and checked and there was a superseded starter. This made sense since I was having trouble, but now $500 and there were only 4 in the country left. So they gave me a discount and I ordered the kit. Installed the starter and the gear jumped up and just barely turned the engine over.

So now I spent nearly 600 on a new battery to replace the old, a bad breaker that would not reset and stayed open, a starter replacement for known bad starters and the problem of the motor not turning over completely still persists. So now I am a bit frustrated. Today I went over the electrical and have all the proper voltage and continuity to the starter circuit. Battery full charged. Then I put a socket on the crank and tried to turn over manually and I can get about 180 degrees and it just stops hard like metal on metal. So now I suspect I'm really screwed. This is obviously why the starter would not turn it over as it got to this point and just locks up and clicks.

What now. All the dealers nearby in SE WI rape you for engine repairs. I fix my tractor motors but am not an outboard expert and not sure where to start.I'm taking a deep breath and will try to figure out what went bad here. Can anyone give advice on how to diagnose a motor that stops hard at one point up when trying to manually turn over?

 

[Silvertip]

Pull all of the spark plugs and see if you can turn the engine. If not, there is something dreadfully wrong inside the motor. It could be anything from a brokenor slipped timing belt and the valves are hitting a piston. It could be a partial seizure due to a failure of the oiling system or fuel getting into the oil via a bad pressure regulator. The reason the starter cracked is because it tried to get past the point where the engine failed to turn. Something had to give and in this case it was the starter. To be on the safe side, do not try and force the engine past that sticking point. The key is to determine WHY it is sticking and there really are not that many reasons for it. Most of them are expensive. Failure to be able to turn the engine manually with the plugs out is almost never a good sign.

 

[rebmo]

Thanks so much for the reply Silvertip. I pulled the plugs and the bottom cylinder was literally filled with gas. I tilted the trailer/motor to drain the gas out. The other 3 cylinders had no gas in them that ran out. There was also gas running out of the intake manifold. I did some googling and one possibly is a leaky hose in the fuel regulator. I ordered new plugs and oil & filter. The motor turns with the fuel emptied. The cracked starter housing makes sense as well as the locked cylinder. I'm going to drain all the fuel and also take the fuel regulator apart and inspect for the leaky vacuum hose described on another posting with the exact same problem.

You are right on target with the "bad pressure regulator" I believe, I just have to dig into that next. It's pouring rain so I have to wait until possibly tomorrow to get the fuel regulator apart. When the motor was turning and would not start there was a point where I smelled lot's of gas. I assumed it flooded. But I had really limited the cranking to not kill the starter (so much for that). If the regulator ruptured and locked the cylinder, that seems to match the symptoms.

Any other suggestions on what to look for when pulling the regulator apart? (other than a blown/leaky hose?)

Thanks so much for the advice. Glad it's not a mechanical lockup, but need to be careful the problem is gone and washed down oil is then replaced with the new plugs & gas.

 

[hemi rt]

You hydra locked a cylinder. The thing to watch out for now is a bent rod, you can compress air but not a fluid so something has to give. One way to check it is measuring the drop of the piston on a good cylinder versus the flooded cylinder. Take a plug out of a dry cylinder. turn the crank until the piston is all the way down or all the way up. measure from the spark plug seat to the top of the piston, now do the same on the flooded cylinder. They should be within a few thousands of an inch. any more and you've got a bent rod which should be fixed before trying to start if. Of course your measurement on the flooded cylinder will be greater than the normal cylinder

 

[rebmo]

Thanks Hemi RT,

Great tip on the bent rod. I'm hoping that's not the case since the motor turned over fine and killed the battery. Then after that point it would not turn over with a weak battery when the lower cylinder filled. I will measure today since all the plugs are out drying out the lower cylinder.

I'm going to examine the fuel regulator and see if the vacuum tube is compromised which from what I've read on another post can be the cause of the fuel getting into the intake and the lower cylinder. I'll check the piston travel to make sure the rod is not bent on the lower cylinder and get a little oil in there. Then I'll change the oil and put some new plugs in (coming in about 3-4 days).

So the good news so far is the symptom (hydra locked piston) seems to be identified. The cause needs to be nailed down (checking the fuel regulator). If that's the problem then need to check for other issues (bent rod lower cylinder), contaminated oil (will change that), dry cylinder (will put a little oil or fog in the lower cylinder when dry).

I'm also thinking of draining the fuel as it's about 1.5 years old now and some older mixed in, and we have 10% ethanol crap gas here which some of it is. I can get ethanol free gas at a station about 30 miles away and I think I'm going to use that going forward. Some of the gas I have in there is ethanol free and it's treated with the Mercury gas treatment each year.

I'll post as things progress. Open to any other things to check before I get things back together.

BTW, the dealer indicated that a new starter replacement kit is what I now have (it's a different starter that frame bolts to the block and is not clamped. It also has a heavier top cover) They said there are only 4 available in the USA and thought that was strange. There might be a run on these starters, and hopefully not due to the problem I'm having.

 

[rebmo]

So the vacuum line inside the fuel regular/pump housing ruptured (defective Mercury OEM line). This cheap hose (great design Mercury) rupturing sucked up fuel from fuel pump housing and filled up the intake manifold and lower cylinder. Whoops, this tiny hose isn't cheap, just the quality is, it costs $20. This hydra locked the engine and damaged the starter. So after tearing down the fuel pump/regulator housing and finding this defect I discovered another Merc design defect. The air filter had a finger size hole in the foam. I touched the foam and it was all crumbling. So I went to order another filter and found these OEM Merc filters were defective and the foam gets sucked into the motors. Great. So to add insult to injury, the new design air filter is $80 (for an air filter?). It's half that for my Tundra?

I contacted Mercury and they basically let me know the won't help me since it's of warranty even though their design defect (hose) destroyed my starter, left me stranded for hours, and did who knows what damage to the lower cylinder, and has my boat down for weeks. Mercury was kind enough to point out that new revision parts were available to fix their defect and they would sell them to me at full price. You think they'd help with the parts price even. Nope. Thanks Merc, buyer be aware.

So as long as I have the motor down, are there any other Mercury design defects I should be aware of and fix before something else falls apart. Thanks for any advice.

 

[Silvertip]

You need to stop worrying about ethanol. It did not have anything to do with the issue.

 

[rebmo]

The defective design air filter also had nothing to do with the hydra lock but I replaced since it was a bad design gone bad. The ethanol fuel also was smelling bad so just noting I replaced it. No worries, thanks for the help on the fuel regulator tip, the defective vacuum hose was the issue.