Hydrolock while running on plane?

[JWhit]

I have a 1993 Caravelle FS with the 4.3L V6. At the beginning of this season changed all of the bellows, gimbal bearing, shift cable, as one of the bellows was leaking. Got it out on the water, leak fixed, but while running at about 3500 rpm the motor just shut off immediately and quickly. Tried to restart and motor wouldn't turn over. After sitting a few hours was able to get it to restart at the dock and idled fine. Figured bad gas, pumped the tank to the best of my ability and filled with ethanol free gas. On the next ride it stalled out a few times in similar fashion, but restarted after only a few minutes each time. This past Saturday it died again and 3800 rpm and would not restart, but i was unable to pull the plugs on the water to relieve pressure.

Any ideas on the possible issues, could it still be bad gas and would that cause sudden seizure while running? Possibly riser gaskets leaking and letting water in while running? Thanks for any advice!

 

[81 Checkmate]

Re: Hydrolock while running on plane?

What does the engine oil look like?

I take it this is a salt water boat!

 

[JWhit]

Re: Hydrolock while running on plane?

Engine oil looks fine with no sign of water, and I've only had the boat one year on all fresh water. According to the paperwork it's been fresh water most of it's life, but you never know.

 

[haulnazz15]

Re: Hydrolock while running on plane?

You said "hydrolock", but was there actually water found in any of the cylinders after you pulled the plugs?

 

[TilliamWe]

Re: Hydrolock while running on plane?

You said "hydrolock", but was there actually water found in any of the cylinders after you pulled the plugs?

And the first few times it did it, it would have NEVER restarted with water in the cylinders.

 

[haulnazz15]

Re: Hydrolock while running on plane?

And the first few times it did it, it would have NEVER restarted with water in the cylinders.

I agree, it likely would have bent some internals. He just said it "seized" and then he pulled the plugs to "relieve the pressure". It doesn't sound like hydrolock unless streams of water came out of the spark plug holes when he cranked the engine over without plugs in.

 

[TilliamWe]

Re: Hydrolock while running on plane?

I agree, it likely would have bent some internals. He just said it "seized" and then he pulled the plugs to "relieve the pressure". It doesn't sound like hydrolock unless streams of water came out of the spark plug holes when he cranked the engine over without plugs in.

yep, we are thinking the same way.

 

[JWhit]

Re: Hydrolock while running on plane?

i wasn't able to pull the plugs, didn't have any tools with me. i am going to bring that along for next time, but can't think of anything else that could csue the motor to seize while running, but sound normal upon a later restart. so no evidence of water yet, just my initial assumption and the fact that it wouldn't restart immediately

 

[haulnazz15]

Re: Hydrolock while running on plane?

i wasn't able to pull the plugs, didn't have any tools with me. i am going to bring that along for next time, but can't think of anything else that could csue the motor to seize while running, but sound normal upon a later restart. so no evidence of water yet, just my initial assumption and the fact that it wouldn't restart immediately

If it was truly hydrolock, the water in the cylinders wouldn't have likely drained. There are other things that could cause the sudden stop of the engine, like a coil failing or an ignition short.

 

[tpenfield]

Re: Hydrolock while running on plane?

Hydrolock at those speeds would be more of an explosion than anything else. So the things to check are fuel and ignition. I'm thinking water in the gas or a loose electrical connection in the ignition system (somewhere ???)

 

[JWhit]

Re: Hydrolock while running on plane?

would something loose on the electrical side cause it to not turn over though? maybe it still is bad gas, and guess the only way to know for sure is to remove the tank somehow to clean, or run on temporary tank for a little while? thanks for all the input so far!

 

[haulnazz15]

Re: Hydrolock while running on plane?

would something loose on the electrical side cause it to not turn over though? maybe it still is bad gas, and guess the only way to know for sure is to remove the tank somehow to clean, or run on temporary tank for a little while? thanks for all the input so far!

How about a faulty ignition key-switch or associated wiring?

 

[JWhit]

Re: Hydrolock while running on plane?

it's not a dead battery type sound when trying to restart, starter engages just doesn't turn the motor over. hopefully i'll have a chance to work on it soon to test for water

 

[boat1010]

Re: Hydrolock while running on plane?

Just like some of the others have said. If it were to hydrolock at that RPM you would not be restarting that motor. Water does not compress. When the starter ingages but does not turn over the motor it could be a low battery. Pull all the plugs and try turning it over by hand or with the starter. It should turn over pretty easy.

 

[26aftcab454]

Re: Hydrolock while running on plane?

this was mine that hydrolocked at 3200rpms--the impeller was worn but not terrible-but one of the Y-pipe water shutters had turned to mush and think it was the culprit.

 

[JWhit]

Re: Hydrolock while running on plane?

hopefully mine is not too far gone, guess we'll see if i can turn it over on Friday. I think if it is not blown already, i'll check the water shutters as you mention. any tips to check/replace those? Thanks!

 

[haulnazz15]

Re: Hydrolock while running on plane?

I think you just need to focus on getting it started. I would pull all of the plugs and crank the engine over (remove the coil lead from the distributor). If no water comes spraying out of the cylinders, you don't likely have a hydrolock issue and can move on to something else. I would check the oil dipstick for water/sludge again just to be sure. Once those two items have been verified good. I would be changing the water separator filter/fuel filter and possibly looking at draining the fuel tank of all of its contents to eliminate water intrusion in the fuel system. Finally, if those items have been taken care of, I would be looking at ignition system (points/coil/wires/ignition switch).

 

[TilliamWe]

Re: Hydrolock while running on plane?

Also, that BIG plug on Mercruisers can get loose and just hitting a wave can cause a total engine shutdown.

 

[joewithaboat]

Re: Hydrolock while running on plane?

View attachment 150439 this was mine that hydrolocked at 3200rpms--the impeller was worn but not terrible-but one of the Y-pipe water shutters had turned to mush and think it was the culprit.

Id be very interested in knowing how broken shutters or worn impeller can cause this.

Ive had both before and probably will again.

As to the o/p, like others i think your problem is in fuel or electrical....

 

[HT32BSX115]

Re: Hydrolock while running on plane?

Id be very interested in knowing how broken shutters or worn impeller can cause this.

Ive had both before and probably will again.

As to the o/p, like others i think your problem is in fuel or electrical....

I Agree with that.

A hydrolock when the engine is running is usually caused by ingesting it. (Any water already in the exhaust is blown out with the exhaust!)

On shutdown it's usually caused by water running back through the exhaust from a leaking (cracked) manifold/riser or gasket.

Water can also get in during a rapid deceleration/shutdown at high speed.

but while running at about 3500 rpm the motor just shut off immediately and quickly.

This is the high speed shutdown........... Even exhaust "shutters" don't completely protect from this.....

Tried to restart and motor wouldn't turn over. After sitting a few hours was able to get it to restart at the dock and idled fine.

Here's the hydrolock resulting from that high speed shutdown. and the subsequent restart after the little bit of water finally leaked past the rings.




The same thing can happen if you turn the key off when on a plane or you pull the safety "kill" lanyard

Cheers,


Rick