Tytan
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Less than 15 minutes--- DEAD IN THE WATER.. possible causes??
- Thread starter Jonathan Lee
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TplusR
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Tytan
Active Member
That's an odd reference because when the rocker shaft is installed you can feel the rocker arms open some of the valves as the rocker shaft bolts are tightened. I have replaced the valves on two 4Tec machines, after reinstalling the cam and rocker assembly in the head you can see some valves open this is before the head is reinstalled on the block. Take a look at a camshaft at any point in it's rotation there will always be a lobe sticking up which will hold a valve open. Any four stroke engine always has some valves open at rest.
Tytan
Active Member
If the exhaust valves are all closed then why do we have to clamp the water line to stop water getting into the engine ?
TplusR
New Member
So the exhaust manifold and ports on the head don't flood which would allow water into the cylinder as soon as it was cranked. Also to prevent any corrosion that would occur after the head was flooded, especially from salt water.
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Ok,,, I got the answer.. This has been bothering me since the moment we had conflicting information within the post. And the answer is,, we are both right.. LOL
The 4-tech engine is specifically to stop rotation at a point where all the valves are closed when you either push the STOP button of the lanyard is pulled off. SO,, I am correct that they are mechanically driven and do not some how magically closed when the engine is turned off. They only way this was posable would have been electronic valves and or to allow for some sort of hydraulic bleed off "assuming" they were hydraulically operated. Which they are not, they are direct connection from the cam tot he cam follower. So bottom line is, if they ignition system is doing its job properlly, the engine will in fact stop with ALL VALVES in the closed position. Good post,,, made me do some thinking and digging...
The 4-tech engine is specifically to stop rotation at a point where all the valves are closed when you either push the STOP button of the lanyard is pulled off. SO,, I am correct that they are mechanically driven and do not some how magically closed when the engine is turned off. They only way this was posable would have been electronic valves and or to allow for some sort of hydraulic bleed off "assuming" they were hydraulically operated. Which they are not, they are direct connection from the cam tot he cam follower. So bottom line is, if they ignition system is doing its job properlly, the engine will in fact stop with ALL VALVES in the closed position. Good post,,, made me do some thinking and digging...
In theory, yes. I have done LOTS of looking and reading on this. If you don't pinch the hose, no water will enter the engine. UNTIL,,, you crank the engine. I'm still doing additional digging as again, in theory, the only water should be water that made it through the hose and is resting in the exhaust ports. Which, again in theory, should be blown out the exhaust once the engine cranks. So,, what I am looking for now is, is there any place that both the exhaust and intake cross paths.
Jonathan Lee
New Member
Wow-- This is fantastic info... if I only had a Seadoo that ran..=( J/K.. This is really good to know if I ever do get to ride! Thanks for all the help gents
Contacted a specialist with the 4-tech and here is why he states we MUST STILL pinch the water tube even though the vales are in fact closed when the engine is not running.
When the vessel is being driven under its own propulsion the jet unit supplies water around the exhaust system and intercooler if applicable.
This cooling water is then dispelled from the system by the exhaust pressure.
If the engine is not running but the vessel is still moving through the water the effect of the water moving through the jet pump forces the sea water through the system and fills it up completely including the exhaust manifold which is meant to stay dry.
This build up of water can cause issues when trying to restart the motor as the water creates a barrier that prevents exhaust gasses from leaving the cylinder thus preventing it from running, also the water sitting on the back of the exhaust valves can potentially leak into the cylinder during cranking which in turn can cause obvious damage to the engine components and further prevent the motor from running.
The clamping of the inlet pipe is a precautionary measure to prevent the system filling if the vessel is being towed for prolonged periods or at cruising speed, however short tows at idle speed typically do not cause an issue.
I hope that the above is an adequate explanation.
When the vessel is being driven under its own propulsion the jet unit supplies water around the exhaust system and intercooler if applicable.
This cooling water is then dispelled from the system by the exhaust pressure.
If the engine is not running but the vessel is still moving through the water the effect of the water moving through the jet pump forces the sea water through the system and fills it up completely including the exhaust manifold which is meant to stay dry.
This build up of water can cause issues when trying to restart the motor as the water creates a barrier that prevents exhaust gasses from leaving the cylinder thus preventing it from running, also the water sitting on the back of the exhaust valves can potentially leak into the cylinder during cranking which in turn can cause obvious damage to the engine components and further prevent the motor from running.
The clamping of the inlet pipe is a precautionary measure to prevent the system filling if the vessel is being towed for prolonged periods or at cruising speed, however short tows at idle speed typically do not cause an issue.
I hope that the above is an adequate explanation.
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