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Hi guys,
Had a bit of an incident on the weekend, someone may have some ideas about what may have happened.
We launched the boat and proceeded out of the 6 knot zone probably only 300m or so away, usually by this stage the boat is up to 140-150deg F almost operating temp. As we powered up the boat went into lip mode due to overheating. the temp was around 190deg F. We immediately shut down, this has happened before due to a faulty impeller or airlock in the cooling system and also not having the water intake sea **** completely opened.....so we weren't too concerned at this stage, when this has happened before we have let the boat cool, worked out the problem and were back up and running.
From memory, before when this has happened and the engine has been cooling the rubber exhaust pipes have contracted and expanded while cooling. (like someone breathing in a paper bag) This time when the engine was cooling the exhaust pipes only contracted & stayed contracted.
So we waited until the boat cooled to 170deg F and tried to start the engine, the starter attempted to start but would not wind over. After a few more attempts we conceded and paddled by way of wakeboard back to the ramp... :x
Once we got back home we began to try and trouble shoot what had gone wrong. By then possibility of hydro lock was considered so we removed the spark plugs.... cylinder 2 & 6 both had water in them. Hence the engine not wanting to wind over. So far we have tried a few things to work out why water has got into the cylinders.
- removed the oil. - pretty much black oil little to no sign of water so we don’t think it’s a blown head gasket.
- removed the exhaust manifold / riser. - Gaskets seemed to be sealing (need replacing now we have removed them though).
So this leaves us with the scenario that water was drawn back up the exhaust by the hot air in the engine cooling and siphoning water into the cylinders.... I originally thought that pcm motors had anti-siphon valves fitted to the exhausts, but after looking closely there doesn’t appear to be any fitted.
On the other issue of overheating we also checked
- Water pump impeller – checked out fine, almost new still
- Thermostat – tested & working.
- Debris strainer – not clogged.
We have also cleared the cylinders of water by cranking the engine by hand and then cranked the engine by the starter motor, it all seemed to crank freely so it doesn’t appear any valves where bent or anything.
So our plan of attack is to replace the gaskets on the exhaust manifold/riser put everything back together, test it on the trailer and then water test it.
Has anyone had similar problems or suggestions? Thanks.
Had a bit of an incident on the weekend, someone may have some ideas about what may have happened.
We launched the boat and proceeded out of the 6 knot zone probably only 300m or so away, usually by this stage the boat is up to 140-150deg F almost operating temp. As we powered up the boat went into lip mode due to overheating. the temp was around 190deg F. We immediately shut down, this has happened before due to a faulty impeller or airlock in the cooling system and also not having the water intake sea **** completely opened.....so we weren't too concerned at this stage, when this has happened before we have let the boat cool, worked out the problem and were back up and running.
From memory, before when this has happened and the engine has been cooling the rubber exhaust pipes have contracted and expanded while cooling. (like someone breathing in a paper bag) This time when the engine was cooling the exhaust pipes only contracted & stayed contracted.
So we waited until the boat cooled to 170deg F and tried to start the engine, the starter attempted to start but would not wind over. After a few more attempts we conceded and paddled by way of wakeboard back to the ramp... :x
Once we got back home we began to try and trouble shoot what had gone wrong. By then possibility of hydro lock was considered so we removed the spark plugs.... cylinder 2 & 6 both had water in them. Hence the engine not wanting to wind over. So far we have tried a few things to work out why water has got into the cylinders.
- removed the oil. - pretty much black oil little to no sign of water so we don’t think it’s a blown head gasket.
- removed the exhaust manifold / riser. - Gaskets seemed to be sealing (need replacing now we have removed them though).
So this leaves us with the scenario that water was drawn back up the exhaust by the hot air in the engine cooling and siphoning water into the cylinders.... I originally thought that pcm motors had anti-siphon valves fitted to the exhausts, but after looking closely there doesn’t appear to be any fitted.
On the other issue of overheating we also checked
- Water pump impeller – checked out fine, almost new still
- Thermostat – tested & working.
- Debris strainer – not clogged.
We have also cleared the cylinders of water by cranking the engine by hand and then cranked the engine by the starter motor, it all seemed to crank freely so it doesn’t appear any valves where bent or anything.
So our plan of attack is to replace the gaskets on the exhaust manifold/riser put everything back together, test it on the trailer and then water test it.
Has anyone had similar problems or suggestions? Thanks.
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