Hydro Lock Exhaust Problem
02-12-2004, 09:58 AM
#1
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Hydro Lock Exhaust Problem
Has anyone ever heard of a boat "Hydro Locking" in the exhaust?
Basically I understand that when the boat comes off plain it is possible for water to back up throught the thru-hull exhaust and get into the engines and blow the motor. This is most common on boats where the thru-hull exits under the swim platform.
Now there is supposed to be a butterfly in the exhaust that prevents this, but in some cases, if the conditions are right, it can still happen.
What precautions can one take to ensure that this never happens again?
Get rid of the thru hull with a Quick and Quiet?
Some type of riser?
Any information?
Basically I understand that when the boat comes off plain it is possible for water to back up throught the thru-hull exhaust and get into the engines and blow the motor. This is most common on boats where the thru-hull exits under the swim platform.
Now there is supposed to be a butterfly in the exhaust that prevents this, but in some cases, if the conditions are right, it can still happen.
What precautions can one take to ensure that this never happens again?
Get rid of the thru hull with a Quick and Quiet?
Some type of riser?
Any information?
02-12-2004, 11:19 AM
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Sometimes coming off plane with the throttles closed and the engines at a high RPM will cause the exhaust to scavenge water up the exhaust pipes...This can happen if there is a big overlap in the cam timing. I'd suggest getting and installing the rubber flaps on the ends of the through hull exhaust pipes and being careful coming off plane... it seems that with some boats .. just as it is coming to a stop... there is a huge wave from behind that will swamp the stern. I've seen this on a 30' Scarab.The trick to not getting the stern swamped was to throttle up just as the wave was coming and the stern wouldn't get covered with water.Then you can proceed at a wakeless speed and not worry about water scavenging into the exhaust. Good Luck.
02-12-2004, 11:48 AM
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What about at the dock. The exhaust is only 1 # from the water line. The rubber flap probably wouldn't stop a small surge of water at the dock (not running) then the water can still get in the engines, right? Someone told me to get some risers? Is that logical, nearly $1200 for parts that I am not sure are necessary.
02-12-2004, 11:51 AM
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It happened to my 30 Scarab. I was running hard when I looked down to see one temp gauge at 240. I shut down the throttles and switched off the hot engine before the boat had a chance to settle. My theory is the water starts up the tailpipe and as it cools, the exaust creates its own suction and draws the water right into the engine. A few minutes later, I tried to start the engine but it wouldn't turn over. I thought the engine was seized. By the time the marine repair guys looked at it the engine was rusted, ruined.
The same thing happened to a friend with a Baja 240 Sport. He was running at high speed when his throttle linkage jammed wide open. Thinking calmly he switched off the key. Sure enough his engine lockd up too. Since I had just had my experience, we decided to pull the spark plugs. Sure enough, water! After we got the water out, the engine started up and ran fine. Wish I had known about this sooner.
The same thing happened to a friend with a Baja 240 Sport. He was running at high speed when his throttle linkage jammed wide open. Thinking calmly he switched off the key. Sure enough his engine lockd up too. Since I had just had my experience, we decided to pull the spark plugs. Sure enough, water! After we got the water out, the engine started up and ran fine. Wish I had known about this sooner.
02-12-2004, 12:06 PM
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So what I am gathering, so far, is that it's not necessary to spend big bucks to stop this from ever happening as long as you are aware that it can happen, and how to prevent it, or fix it if it ever does happen.
These types of thing make me glad that I didn't have thru-hull on my last boat.
Let me ask you this, if the boat needed to be shut off immediately while it was running at high speed, and it was equiped with Quick and Quiet exhaust, could the thru-hull have been closed to prevent problems?
These types of thing make me glad that I didn't have thru-hull on my last boat.
Let me ask you this, if the boat needed to be shut off immediately while it was running at high speed, and it was equiped with Quick and Quiet exhaust, could the thru-hull have been closed to prevent problems?
02-12-2004, 05:15 PM
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02-14-2004, 01:10 PM
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What are they going to fix me up with?
I called BAM and they said that I better have an Mercruiser mechanic check it out because there must be some kind of leak or problem that can't be resolved over the phone.
Fact is, I will fix it myself, or sink it before I call a mechanic.
I called BAM and they said that I better have an Mercruiser mechanic check it out because there must be some kind of leak or problem that can't be resolved over the phone.
Fact is, I will fix it myself, or sink it before I call a mechanic.
