Mercury XR6 Woes

Hello Everyone!

I recently purchased a boat with a 150hp XR6 Mercury engine. The engine ran fine until just a few days ago. I noticed when I first bought the boat, that the tach didn't work. I read online that this was due to the voltage regulator failing or being on its way out. I decided to swap the tach send from one regulator to the other and the tach worked fine... but it only worked for a few minutes and then quit!

The next day, I took the boat out to the lake and after I got on plane I went wide open trottle and got it up to 50-55 mph. The boat suddenly started losing power and I quickly put it in neutral fearing the worst. After a few seconds the engine died on its own. I tried to turn the boat over and I only heard a clicking noise.

After waiting for a few minutes... I tried to start the boat and it ran great at idle so I tried to get back on plane and stay at around 30 mph, but the boat did the same thing! It lost power and died! After this happened, the boat wouldn't start and I had to use the trolling motor to get back to land (2-3 miles away).

I checked the voltage gauge and the batteries were around 10-20% and when I checked them before heading out it had said 50-60%


While I was still at the lake I took the engine cover off and I noticed that the bendix on the starter was stuck up! I hit the starter a few times and got the starter to kick back down.

Once I got to the boat ramp I swapped out the battery with the trucks and tried to see if it was the batteries that were the problem. This did not help and the starter kicked up and started to turn the flywheel a little bit, but the boat would not turn over completely.

I wiggled the flywheel back and forth and got the Bendix to kick back down and I then tried to manually turn the flywheel. The engine however, wouldn't turn completely over. It would turn fine and then "hit" something and I would turn it around the other way and it would "hit" something again.


So my main questions are this.

1. Could the problem be electrical? If so, what should I check first? Is there a sensor that prevents the engine from turning over completely, even by hand?

2. Is it possible that the engine isn't turning over because the boat is still "stuck" in gear? By this I mean the boat may have "died" while in gear (I don't remember). If I put it in neutral with the boat "off" would the transmission still be engaged?

2. If the safety switch is in the "off" position, will the engine turn over as long as you turn the key?


3. When I first got the boat, you couldn't leave the engine in the "crank" position indefinitely. If the engine didn't start after a few seconds you would have to wait to try again. If I tried to turn the key to the "crank" position instantly after it didn't start, it wouldn't even click. Is this some sort of safety feature that might be preventing the engine from turning over completely?

4. Could my engine be done? I thought an engine wouldn't move even slightly in either direction if it was "seized" or had thrown a rod.



I appreciate any help I can get! Thank You!

1 - you may have some electrical issues, along with something else. There is no "sensor" that prevents the engine from turning over. Some models have a neutral safety switch which will prevent power from being sent to the starter and yet others that "lock" the flywheel (usually small horsepower motors). On those that lock the flywheel it won't move "at all".

2 - If you shifted back to neutral there is nothing that would keep it in gear unless you had a broken shift cable, broken shifter or some mechanical issue with the gears etc.

3 - with the safety switch set to "off" the motor should turn over all day (or at least until the battery dies) but will not fire. It sends the power, that normally goes down to the spark plugs, to ground - otherwise, everything works "like it should be running".

4 - crank position indefinitely - again, no safety feature there that I can think of - sounds like you may have a bad keyswitch is "addition" to other issues.

5 - your engine could be seized - maybe??

Remove the sparkplugs and see if you can turn it over by hand - that way you are not fighting the cylinder compression (which you may have mistaken for a "hitting something".

Hopefully you didn't buy a pile of scrap that someone got to run with some "snake oil" long enough to get it sold.

Private sale or dealer?? if the latter, I would be giving them a call...

Remove the plugs, do a compression test.
If it doesn't turn over after the plugs have been removed, drop the lower unit and see if it turns then.
Post the results.

Pull the oil drain plugs on gearcase and see if its has metal slivers as gearcase may have took a dump. Sounds more like a powerhead seize but check gearcase anyway...

I ended up taking off one of the cylinder heads and the worst case scenario was indeed confirmed.


The engine appears to have completely melted the very top starboard side piston.

While I was under the cowling I went ahead and did a compression test and the rest of the engine appears to test at 120.

I have attached some pictures!

1. Does anybody know what may have caused this failure? How can I diagnose the possible cause?

2. It appears that there are crosshatch markings on the other cylinders. Does this mean that this engine has been rebuilt previously?

3. Will I be able to hone or bore the "bad" cylinder, or will I need to replace the entire sleeve?

4. Will I be fine with just replacing the "bad" cylinder and rod without having to touch the rest of the engine? (The rest of the engine cylinders all tested at 120 PSI)















Thanks in advance for any advice or feedback you can provide!

I ended up taking off one of the cylinder heads and the worst case scenario was indeed confirmed.


The engine appears to have completely melted the very top starboard side piston.

While I was under the cowling I went ahead and did a compression test and the rest of the engine appears to test at 120.

I have attached some pictures!

1. Does anybody know what may have caused this failure? How can I diagnose the possible cause?

2. It appears that there are crosshatch markings on the other cylinders. Does this mean that this engine has been rebuilt previously?

3. Will I be able to hone or bore the "bad" cylinder, or will I need to replace the entire sleeve?

4. Will I be fine with just replacing the "bad" cylinder and rod without having to touch the rest of the engine? (The rest of the engine cylinders all tested at 120 PSI)















Thanks in advance for any advice or feedback you can provide!