Slamming outboard(s) into reverse and hydrolocking the engine(s).

[Philster]

Re: Slamming outboard(s) into reverse and hydrolocking the engine(s).

seahorse5, do you know if these boats had a single throttle/shifter or dual controls?

That is fascinating. We get bogged down thinking about basic mechanics and forget how electronics come into play...

 

[seahorse5]

Re: Slamming outboard(s) into reverse and hydrolocking the engine(s).

single controls are the most common in today's boats

 

[glenn property of pam]

Re: Slamming outboard(s) into reverse and hydrolocking the engine(s).

fun post to read. i have a lower 70 hp lower unit in the yard that was switched from full forwards to reverse on a 2 stroke and the big dent in the side of it shows where the gears tryed to get out the lower unit. if the gears survived then the rotating mass of the crank, flywheel, shaft verses the rotaing mass of the gear and prop comes into play. the question is how fast does a engine have to be running to bend a rod with a hyro-locked piston. if it stalled and ran backwards would it have enoght mass/speed running backwards to bend the rod (carnt see it running many rpm as theres still a point where both valves would be closed causing resistance to the pistons movement, now im just driving my self nuts trying to work the valve movements in reverse order)

 

[gil60]

Re: Slamming outboard(s) into reverse and hydrolocking the engine(s).

There is some heated discussion going around in other places I won't mention.

Nonetheless, the non-disputed facts go like this:

Outboard-equipped boat running on plane. Debris or other sudden panic-inducing issue causes operator to slam throttle to neutral and then reverse almost immediately, or from forward to reverse. There are documented cases of this causing the engine or engines to hydrolock. In the cases I've read, they are Yamaha o/b engines. Yamaha has even warrantied some engines that have hydrolocked (engines had bent con rods and other damage).

The disputed facts:

Water entered the engine via the exhaust vs. water entered the engine via the intake.

There are two camps that align themselves with one explanation or the other. "There is no way water can come up via the exhaust; not just by slamming it into reverse; it came in via the intake!" vs. "There is no way it can enter the intake; these must be cases of it coming in via the exhaust!"

There is another delusional camp that believes the engine ran in reverse cycle (internals rotating opposite of norm). Since these are four-stroke o/b engines, I prefer to discard this possibility, but would entertain the theory for a moment, if we were talking about 2-strokers, as they can run in reverse (we 2-stroke engine builders call that 'dieseling').

I wanted to get iboaters' takes on this issue. Because owners are relaying the information, there isn't much extra detail (for example, if it happened to me, I'd want to know more about where the water was actually found. Surely, if the engine ingested water via the air intake, I'd expect evidence of that and lack of that evidence might point me to the exhaust).

Please opine. I lean towards water ingestion at the intake, but I also know there are always chances for water reversion at the exhaust.

I did the exact same thing .. I came upon a partially submerged tree and jammed the throttle back to neutral and the motor died immediately. Since I was having some electrical issues i thought nothing of it thinking that the batteries had just died on me. So now I have a 225 Yamahahaha that is as useful as a brick... i can find no one, including my mechanic who has maintained my unit for the past 7 years who will agree with the surveyor who was sent by my insurance company to look at this thing.

 

[JB]

Re: Slamming outboard(s) into reverse and hydrolocking the engine(s).

You have violated rule #12, Gil. Please read and respect our rules.

Thanks for your cooperation.