43 Hydrolocked

"Engine dieseled (like usu

"Engine dieseled (like usual) on shut off, this time a bit longer, I'm guessing it sucked water in thru the intake then filled all 6 cylinders full of water. We pulled the plugs out and pumped most of the water out.
-How can we get the remaining water out?
-What are the next steps to take?
-What damage could have occured?
-Any other suggestions?"

"Are you suggesting that the e

"Are you suggesting that the engine dieseled (and spun in reverse) pulling water in from the exhaust manifolds?

If so, this motor won't be the same... but i can take you through some steps that you could take that would make it run again."

That is what the mercruiser ma

That is what the mercruiser manual suggested. Have you heard of this before? Does this mean major engine work?

"Yeah, it is the same. Remove

"Yeah, it is the same. Remove the plugs and crank it over for about 10 seconds. Pretty common on motors that haven't had the run-on issue addressed properly.

Do a search here for a thread that includes info about the Mercruiser service bulletin that I posted before. It's right from Merc and is complete. IIRC, the original poster for that thread is named Doug.

If there's water in the oil, get that out, too. Water in the oil is far less common."

"If you are pumping water out

"If you are pumping water out of the cylinders, in all likelihood, it means the engine is ruined. It may run again, but the bearing and cylinder wall surfaces will never be the same again. The wear will intimately show in your compression readings and in low oil pressure.

*pull the plugs
*suck all the water out of the cylinders until you can roll the motor over by hand and it spins freely
*drain the oil/water from the sump and refill
*fog the cylinders with a light oil and replace plugs
*see if it will fire up.
*bring it up to temp and change the oil/filter again

Do this quickly before you get too much rust. You'll still need to address the problem that is causing the dieseling. Just thoughts."

Thanks for the info.
Any more

Thanks for the info.
Any more ideas... Send them over.

"If you didn't keep trying

"If you didn't keep trying to turn the engine over with the water in it the chance of any real damage is small.
On the other hand if you did keep trying the starter there could be some real damage in the form of a bent rod.
Only one cylinder will hydro even if there is water in all the cylinders.
Only one cylinder is at tdc at a time so if that cylinder locked the others can not because they are not as close to tdc on the compression stroke.
It only takes one cylinder to lock the engine.
Also not all of the cylinders can lock because they are not all on the compression stroke at the same time, some are on the exhaust stroke which would push the water out of the exhaust port.
If you removed all the plugs & had water spraying out of all the plug holes while turning the engine over it's because it is easier for the water to exit the plug hole than the exhaust port with the plugs removed.

As stated before spray storage fog or even WD40 into the intake & plug holes & change the oil before you start the engine even if there is no sign of water in the oil. The water will be on the bottom of the pan & not show on the dip stick other than a higher oil level.

There may not be water in the oil but better safe than sorry.

Do not leave the engine without some kind of oil on the cylinders & valves. They will rust in minutes in some cases depending on how damp the air is.


Have the idle mixture / rpm & timing checked. If the idle is to high or the timing is advanced to far it can cause run on.
The idle screws need to be open enough to allow the throttle plate to be closed as far as it can so there is not too much air passing into the intake allowing the run on.
An idle control solenoid is a good way to stop run on. Also try a better grade of fuel & make sure the engine is not running hotter than it should."

Charli's first sentence is

Charli's first sentence is good news. Act quickly before you get rust! Good luck.

Done! It runs as if nothing ev

Done! It runs as if nothing ever happened... So far.
Thanks for the advice!

I'll have to look into an idle control solenoid to stop run on.

good man.

good man.

"Again, look for the thread wh

"Again, look for the thread where I posted the part number, etc for the Mercruiser solenoid kit and the other steps for dealing with this issue. The answer I got when I asked about it in '98 is that they went to a more aggressve cam and it was more prone to hot spots and the problem you are having. I also heard that some of the water injestion issues were caused by some boat manufacturers placing the motor a bit lower in the boat without knowing that Mercruiser had come out with a lower-profile exhaust riser.

There are other solenoids out there that will work and IIRC, there was some mention of a mid-'70s GM car with an idle stop solenoid what worked well for this carb."