So I decided to fire up the boat for the season today. A little background first. I did a 100 hour service before putting it away for the winter. I decided to fog the engine and cranked it a tiny bit to shoot out the excess fogging oil. The only thing I didn't do in the 100 hour service was change the spark plugs ( I know 100 hours is a bit overkill).

So when I went to crank it, it wouldn't crank. It seemed to just jam or bind. Battery was 1 year old, maintained, and charged up. Tried a second time, same thing. I shouldn't have tried a third time, but I did. It slowly cranked and sounded like it was struggling. It fired. Smoked for 15 to 20 seconds (I'm thinking the fogging oil) and smoothed out in about 30 seconds. It sounded like it was running fine to me. I turned it off and started it again. It fired up easily. I was terrified I hydro locked it by putting too much fogging oil in.

I decided to change the spark plugs because it would give me a chance to compression test it. Pulled the throttle wide open and cranked it for each cylinder - 190 on the dot for each one. I finished changing the spark plugs and tested it. Fired immediately and ran smoothly.

I really don't believe I hydro locked it damaged anything, but that just really scared the hell out of me. Any ideas what it could have been?

When you said you cranked it to shoot out the excess oil, I'm assuming you pulled the plugs? I usually do that and watch for the oil to shoot out the cylinders before there's any gas introduced.

Either way, I agree you probably didn't hurt anything. Today must have been the day to get out oards going in New England, I got my boat out of the woods today too.

40 minutes ago, PourMyOwn said:

When you said you cranked it to shoot out the excess oil, I'm assuming you pulled the plugs? I usually do that and watch for the oil to shoot out the cylinders before there's any gas introduced.

Either way, I agree you probably didn't hurt anything. Today must have been the day to get out oards going in New England, I got my boat out of the woods today too.

Yes, I had the plugs removed. I do that to lubricate the rings and cylinder walls as well, but I mostly do it to get rid of excess fogging oil so I don't have issues in the spring. If I did have too much oil in the walls, it probably would've smoked for much much longer than it did.

Not that mercury's vesselview is definitive, but there were no fault codes that popped up when I ran the engine. I even revved it up a few times to 3500 rpms. Sounded fine, no skip, and no faults.

I shouldve mentioned that when I tried to start the engine, I just heard the engine click, like it turned over an inch but was binding. I'm a bit of a worrier, lol. But I just can't make sense of what it could've been.

Only things I can think of so far are:

1. Hydro locking

2. Poor battery connection (I just finger tightened it). But it would start instantaneously on subsequent tries.

3. Corroded/rusty starter

4. Poor battery (it's only 1 year old and I had it on a trickle charger)

5. I under fogged a cylinder/fogging oil didn't work and the rings rusted onto the cylinder wall (I find this the least possible)

I have an old Merc XR 6 150hp (carbureted)

When my engine did the same thing, it turned out to be a bad starter, New starter fixed the problem. The click you hear is the starter solenoid activating or delivering voltage to engage the starter. "It slowly cranked" would be another hint at starter issues.

I hope your problem can be fixed as readily as mine was.

9 hours ago, Nitro 882 said:

I have an old Merc XR 6 150hp (carbureted)

When my engine did the same thing, it turned out to be a bad starter, New starter fixed the problem. The click you hear is the starter solenoid activating or delivering voltage to engage the starter. "It slowly cranked" would be another hint at starter issues.

I hope your problem can be fixed as readily as mine was.

That would really annoy me. The engine is 2 years old. I wonder if finger tightening it gave a poor connection. I just finger tightened it to test out the boat.

My new boat came with an advisory hang tag on the steering wheel and a sticker in the battery compartment warning against the use of wing nuts. At the time I figured it had to do with fire/arcing risk, but now I'm wondering if modern outboards are more sensitive to electrical disturbance. That wouldn't surprise me. Modern outboards are a completely different animal than one from 30 years ago.

6 hours ago, MontanaBasser said:

My new boat came with an advisory hang tag on the steering wheel and a sticker in the battery compartment warning against the use of wing nuts. At the time I figured it had to do with fire/arcing risk, but now I'm wondering if modern outboards are more sensitive to electrical disturbance. That wouldn't surprise me. Modern outboards are a completely different animal than one from 30 years ago.

Maybe a poor connection, although I finger tightened as hard as I can (and I've got tough hands and grip). The more I think about it, it DEFINITELY wasn't hydrolocking. I just didn't spray nowhere near enough to flood the engine and even if I did, cranking it over (before storage) would've gotten rid of it the excess.

So my guess is it's down to 3 possibilities:

1. Poor connection somewhere. (maybe the finger tightened nuts, but I tightened the heck out of them)

2. Weak or failing starter (2 year old outboard!)

3. Weak or failing battery (1 year old battery)

I wonder if anyone experienced a starter that was weak after sitting for a winter.

17 hours ago, Nitro 882 said:

I have an old Merc XR 6 150hp (carbureted)

When my engine did the same thing, it turned out to be a bad starter, New starter fixed the problem. The click you hear is the starter solenoid activating or delivering voltage to engage the starter. "It slowly cranked" would be another hint at starter issues.

I hope your problem can be fixed as readily as mine was.

You're right. It's obviously related to starter health. I wonder if a weak connection can mimic a failing starter.

If you have a remote starter, which most newer Mercs do, oftentimes it needs to be near the main starter button when the motor is started by using that main starter button. The remote can also cause the motor to stop while running if moved out of proximity, or placed in a tight pocket of your pants. Other than that, the remote's battery may need replacement or could be improperly installed.