1993 Luhrs 290 - Hydrolocked

[stevemellett]

Has anyone ever had or heard of getting "hydro-locked". This is where water backs up through your exhaust hose into your exhaust manefold and ending up in the cylinder that has the exhuast valve open. Why is this happening? I recently went shark fishing in moderate seas and both engines became hydro-locked. After removing spark plugs, soaking cylinders with oil and blowing them out, we were able to reassemble everthing and get both engines running in no time. Water was literally pouring out of the cylinders. Is there something I can do to prevent this from happening? I was think of installing some aftermarket "flappers" on my exhaust to help prevent water from getting back in. Help!

[CrazyIslandMoFo]

From what I have heard, this occures due to exhaust risers or elbows rusting out, and the water jacket being compromised, is your boat fresh water cooled w/ raw water heat exchanger?? if your boat is raw water cooled your whole engine block may need to be replaced... I would think it would be nearly impossible for water to make it up the exhaust system enough to swamp the motors... were the motors running when this happend ?

[Esquire]

I believe that you can swamp your engine by getting water backed up through your exhaust. I think it is pretty hard to do it while the engine is running but suppose anything may be possible such as backing down really hard...it would ususally occur drifting, or while at anchor rocking back a forth if the seas are a bit lumpy.. do you have any flaps over your exhaust ports at all? Woudl suggest that you install some as you mentioned if not, just be sure they do not restrict your exhaust flow. Could also happen as CIMF says too but it will happen right away again if you have that kind of problem.

[stevemellett]

There was no water in my oil, so i don't believe that my block, exhaust manifolds or risers. I have fresh water cooled engine with heat exchanger (Marine Power 350 Gas Engines). When I disconnected the exhaust hose from the riser offshore, there was water rushing in as the boat rocked. The motors were off at the time. When I tried to start the motors, it almost seemed like the batteries were dead, because the starter would not engage. I checked the batteries and they were fine, then pulled my spark plugs and water rushed out of the cylinders. I do not have an flaps on my boat. I spoke to John at Lockwood's in Jersey today and he suggested installing Primex In-line Check Valves (MUFCI). This seems like a good start. Still want to know why this is happening though? Seems like a poor design to have to worry about something like this. There is too many other things to worry about offshore.

[CrazyIslandMoFo]

I am curious, what are you running for silencers? I have naqualift... do these change any thing ?? I do have flaps. When the exhaust is below the water line, I wonder if the exhaust lifters have any effect on hydroloc,... is there a sphion effect??? Were you taking heavy seas to the stern? Were all cylnders or all banks to have water?? Thanks for the info...This forum is outstanding!

[chuckm]

You should have flappers on the exhaust ports. The baffles in your muffler are supposed to help control the amount of water that can run back uphill. Due to clearance issues the risers only have a mild slope to them. In a boat with a deeper engine room you can run a taller elbow which gives more protection. Even still you should be very careful about running in reverse as even a moderate following sea can cause water to run "uphill" into the engine. You are very lucky that you did not throw a rod as water does not compress and if the engine tries to run with water in the cylinder the piston rod or valve stem will give under the pressure.

If your risers & elbows are more than 5 years old you could have passages that are rusted out. Also if you have not changed the gasket between the riser and elbows in a couple years the gasket may have failed.

Most likely it's the lack of flappers that are just letting water flow back into the engine. Gets some flappers on ASAP.

Also, beware of a thing called reversion. In most gas marine engines the vaccum at low rpm is enough to pull water up the elbow and back into the valves. This becomes a problem when you turn the engine off after idling as the water puddles around the valves or in the piston and causes rust. To avoid this run the engine up around 1200 rpm prior to turning it off. The exhaust pressure at this rpm will counter the vaccum and blow out the water.

chuck

[stevemellett]

Not sure what I have in there for silencers (I'll check)... they are bicg black fiberglass cans aft of the motors in the engine room. we were drifting in moderate seas 2-3'. at first, only the cylinders with open exhaust valves had water in them, but after removing the plugs, water continued to pour in and flood all cylinders when cranking the engines. I was able to get my motors running back at the dock immediately after drying the plug wires, cleaning the plugs and spraying a bit of starting fluid in the carbs. Both motors are running great.

Thanks for the info too, chuck... good advice. I installed the Primex check-valves yesterday on each exhaust hose close to the stern. I intend to also install rubber flaps on the back of the boat where the exhaust exits the hull. I have to modify the stock rubber flaps to work with the custom design of my Luhr's exhaust ports, as they are molded into the hull. It is probably overkill, but I don't want this to happen again.

[chuckm]

Steve,
You are very lucky that this did not destroy the engines. There is a section in the Luhrs manual on Hydrolock with lots of warnings. I'm surprised that there were no flaps on your boat.

Did you just buy this boat?

Is it a brand new boat?

Is it possible that when the bottom was painted that the yard removed the flaps and did not replace them?

regards

chuck

[witeagle]

The flaps on the 32 open I am about to purchase are missing. There are two flat clamps (one per side) and the rubber is torn off on both sides. I just did a quick search on the net and just found fitted flaps that have a clap on style ring. In this case I just need flaps. Is there a material I can use to just cut my own or pre-cut without the rings.

I am also thinking I can order them from a Luhrs dealer???

[Esquire]

Call Marshall at Luhrs, he is the parts guy and if he has the flaps in stock he will mail them to you. The number I have for him is, 904-827-2030. I needed some small parts for my boat and he got them to me within a week. Good dude.

[davebanks]

How are thy set up originally I have a 38 with detroits and a what i think is a water lock silencer in the exhaust and a flap on one side is this an add on? Or do i need to have flaps?They're 8 inch and dont seem to be easily available even on the net. What to do?
Cheers Dave