2011 Mercury 15 4-stroke internal failure

Airdale

Recruit
Joined
Nov 11, 2009
Messages
3
I purchased a brand new 2011 Mercury 15hp 4-stroke this year from Bass Pro shops in Maryland. They had a good sale going on and I was in need of an outboard for my 14' duck boat. I completed the break in period per the Mercury manual and the break in procedures card I was given. During the break in, I felt like the motor didn't run very smooth. It always started easily and idled just fine, but the lower power range was rough and it didn't seem like it would make full power. It would also surge at low power settings. I didn't stress about it because it was the break in period.

After the break in, I changed the oil per the manual. 1 liter of 10w30 4 stroke oil and a new filter from the local Mercury dealer. I also went ahead and changed the spark plugs in hopes that this may smooth the motor out. After I changed the oil and plugs, I ran the motor hooked up to the flush. I noticed that aside from it running a bit rough, that it also seemed like it had a slight missfire below 1/2 throttle. So yesterday I dropped the boat off at the Merc dealer to have them take a look at it. They said the motor ran fine, but they made a small linkage adjustment because it wasn't getting full throttle.

This morning I took the boat out on the river for a duck hunt. The motor ran as it normally did all the out to the spot where I setup. I shut the motor off, trimmed it all the way up and settled in to hunt for awhile. After about an hour, I went for a ride and the motor shut off. It actually sounded like I had hit something, but that wasn't the case. The motor never shuttered or kicked up, but the way that it shut off was almost as if something grabbed the prop. I went to restart and it wouldn't restart. It took me about a minute to get it running again and when it did start, it had a very loud whine. I shut it off again, inspected the prop, lower unit, removed the cowling and checked for anything obvious. I started it back up again and the whine was still there, only much louder with the cowling removed. I decided I better get back to the ramp and made my way back at 1/2 throttle.

I went to the Merc dealer and the mechanic ran the motor hooked up to the flush right there. He shut it off right away and then checked the oil level, which was normal. The oil still looked brand new. He removed the spark plugs and they showed signs of overheat. A compression test showed that neither cylinder got above 90. He asked me if I ran it through mud and I told him that the whole time I was running, the tell tale never stopped streaming water, I never bumped bottom and I never had to trim the motor up for shallow water. I was an outboard and diesel engine mechanic in the Coast Guard for 4 years and I've been running boats for 20 years, so I'm not a rookie at this. I always check the tell tale frequently when I'm running an outboard.

The motor showed no prior signs of an overheat. The low oil pressure light never came on. The mechanic is going to start looking at it today to find the problem, but it does not look good. My guess is that this motor had something wrong with it from day one. My buddy has the same exact boat I have but he runs a 15 Yamaha 2 stroke. He does 15-16mph on the water, while my Merc couldn't get me over 11mph. The motor has less than 20hrs on it, so I expect nothing less than 100% warranty coverage from Mercury on this, otherwise we're going to have a big problem because I just spent $2,500 on this motor this year. Does it sound like this problem is related to the lack of power? I was a Johnson 2 stroke and Honda 4 stroke mechanic in the Coast Guard, so I'm not familiar with Mercury 4 strokes.
 

SaabFAN

Cadet
Joined
Sep 8, 2011
Messages
16
Re: 2011 Mercury 15 4-stroke internal failure

I'am no expert on this particular motor either, but from what you are telling, i guess you had a "piston-squeezing" (leo.org-translation for "Kolbenklemmer"). This happens when tolerances are not within specifications and can be cased by to much heat, stuck piston-rings that give the piston too much clearance, or insufficient lubrication.
I think, in your case, the last possibility was the cause for the failure. When your engine was not run inside the factory, it is possible, that no part ever saw any oil before you started it. The oil-pump needed some time to pump the oil to every surface and in that time, the engine ran entirely without lubrication, which is a death-sentence inside the break-in period.

The Whine from the engine after it suddenly stopped, is a bearing, that was damaged, when the Piston-Squeezing suddenly stopped the engine.

I suggest, you demand a new engine or at least a new Power-Block from your dealer, because your pistons may be damaged, the connecting-rods WILL BE bent and the same goes for the crankshaft. Add to that all the bearings inside the crankcase and the fact, that there may be a clogged oil-canal inside the block.
In your case, wouldn't trust this engine one more meter without a new Engine-Block!
 
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