2004 Mercury OptiMax: Low Water Pressure After Grounding

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Author Topic:   2004 Mercury OptiMax: Low Water Pressure After Grounding

heatxcape posted 05-31-2010 07:35 AM ET (US)
I have twin 2004 Mercury OptiMax outboard motors. [I] had [the water pump impellers] and [thermostat valves] changed about 20-hours [of engine running time] ago. [U]nfortunatly [the boat] had a soft grouding on a shifting sandbar. [I] shut down the engines immediatly, and, once [I] pushed myself off, the starboard engine started to overheat about 15 minutes later. [I] went to [a] marina and cleaned out the clogged aspirators that were blocked with sand to insure a steady stream. [The Mercury OptiMax motors] ran fine for two hours at both idle and full tilt, but [I] did notice my Smartcraft [gauge or instrument] is showing at idle that my port water pressure is 4.0-PSI and the starboard is 1.8 to 2.0-PSI. psi. [Is the cause of the difference in the readings of water pressure between the two engines due to the] water [pump] impeller or the poppet [valve]?
[S]omeone told me 2.0-PSI at idle is OK, but [I] don't want to be 10 miles out and have [something on the engine] break apart and leave me stranded. [Give me advice]. [I] forgot to add that at idle the starboard [Mercury OptiMax engine] is running about 5 to 10-degrees hotter [that the port engine], which makes me think [that there is a problem on the starboard engine with the water pump] impeller.
jimh posted 05-31-2010 08:17 AM ET (US)
I assume from your narrative that prior to the grounding the starboard and port twin Mercury OptiMax engines showed similar water pressure and similar temperatures. According to your narrative, after the grounding, at idle the starboard Mercury OptiMax now has lower water pressure and runs at a higher temperature.
The water pressure indicator is a measure of the water pump output pressure. The water pump output pressure is an indicator of the volume of water being produced by the water pump and delivered to the cooling system. Lower pressure indicates less water. Engine temperature is inversely proportional to volume of cooling water. You report the engine temperature is higher. All of these observations lead to a conclusion that the water pump in the starboard engine is not producing as much water flow in the cooling system as is occurring in the port engine.
The poppet valve is a pressure sensitive valve that is intended to increase flow of water in the cooling system in order to reduce temperature. If the poppet valve were not operating normally, the most likely result would be the engine would be supplied with too much cooling and its temperature would be lower. This is not consistent with your reported observations, so it seems unlikely that the poppet valve is causing the engine to run at a higher temperature.
heatxcape posted 05-31-2010 04:23 PM ET (US)
Thanks for the info. Yes, both port and starboard pretty much in sync on the water psi. So after the soft grounding, it appears taht i may have damaged the impeller.....unless someone can think of something else.
jimh posted 05-31-2010 07:56 PM ET (US)
Re the water pressure indication--this might also be affected by debris from the sand. Try disconnecting the hose between the motor and the water pressure gauge. Let the motor run for a while, and this should cause water to be pumped through the hose and run from the unconnected end at the gauge. This may flush out debris from the water pressure hose.
As for the water pump impeller, it is hard to gauge how much sand might have been sucked into the cooling system. One would hope that a small amount of sand might be able to pass through the water pump without causing damage. However, from your data about water pressure decrease and temperature increase, it seems reasonable to conclude that the water pump output volume and pressure are lower than normal, or at least lower than the other motor.
heatxcape posted 06-01-2010 01:26 PM ET (US)
in regard to your reply....(low pressure might also be affected by debris from the sand. Try disconnecting the hose between the motor and the water pressure gauge.) I am not that familiar with the inner workings of the Merc Optimax. Can you advise as to how to find teh hose prior to the water pressure gauge?? anyone happen to have a diagram or good directions?
jimh posted 06-01-2010 01:40 PM ET (US)
You can follow the hose from the gauge, or disconnect it at the gauge.
Tohsgib posted 06-01-2010 01:55 PM ET (US)
Disconnect at the gauge if manual. If electronic then it won't matter. If electronic I might try removing the sensor and see if it had goop in there.
10000 Lakes posted 06-04-2010 01:05 AM ET (US)
Save wondering. Drop both lowers and change out both impellers. Spending eighty bucks and a couple of hours labor could save thousands.
Eliminate that first. The fact is common sense here should prevail over mental cures. One engine is running hotter. That says something is amiss for sure besides a tiny water pressure line..

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Author	Topic: 2004 Mercury OptiMax: Low Water Pressure After Grounding
heatxcape	posted 05-31-2010 07:35 AM ET (US) I have twin 2004 Mercury OptiMax outboard motors. [I] had [the water pump impellers] and [thermostat valves] changed about 20-hours [of engine running time] ago. [U]nfortunatly [the boat] had a soft grouding on a shifting sandbar. [I] shut down the engines immediatly, and, once [I] pushed myself off, the starboard engine started to overheat about 15 minutes later. [I] went to [a] marina and cleaned out the clogged aspirators that were blocked with sand to insure a steady stream. [The Mercury OptiMax motors] ran fine for two hours at both idle and full tilt, but [I] did notice my Smartcraft [gauge or instrument] is showing at idle that my port water pressure is 4.0-PSI and the starboard is 1.8 to 2.0-PSI. psi. [Is the cause of the difference in the readings of water pressure between the two engines due to the] water [pump] impeller or the poppet [valve]? [S]omeone told me 2.0-PSI at idle is OK, but [I] don't want to be 10 miles out and have [something on the engine] break apart and leave me stranded. [Give me advice]. [I] forgot to add that at idle the starboard [Mercury OptiMax engine] is running about 5 to 10-degrees hotter [that the port engine], which makes me think [that there is a problem on the starboard engine with the water pump] impeller.
jimh	posted 05-31-2010 08:17 AM ET (US) I assume from your narrative that prior to the grounding the starboard and port twin Mercury OptiMax engines showed similar water pressure and similar temperatures. According to your narrative, after the grounding, at idle the starboard Mercury OptiMax now has lower water pressure and runs at a higher temperature. The water pressure indicator is a measure of the water pump output pressure. The water pump output pressure is an indicator of the volume of water being produced by the water pump and delivered to the cooling system. Lower pressure indicates less water. Engine temperature is inversely proportional to volume of cooling water. You report the engine temperature is higher. All of these observations lead to a conclusion that the water pump in the starboard engine is not producing as much water flow in the cooling system as is occurring in the port engine. The poppet valve is a pressure sensitive valve that is intended to increase flow of water in the cooling system in order to reduce temperature. If the poppet valve were not operating normally, the most likely result would be the engine would be supplied with too much cooling and its temperature would be lower. This is not consistent with your reported observations, so it seems unlikely that the poppet valve is causing the engine to run at a higher temperature.
heatxcape	posted 05-31-2010 04:23 PM ET (US) Thanks for the info. Yes, both port and starboard pretty much in sync on the water psi. So after the soft grounding, it appears taht i may have damaged the impeller.....unless someone can think of something else.
jimh	posted 05-31-2010 07:56 PM ET (US) Re the water pressure indication--this might also be affected by debris from the sand. Try disconnecting the hose between the motor and the water pressure gauge. Let the motor run for a while, and this should cause water to be pumped through the hose and run from the unconnected end at the gauge. This may flush out debris from the water pressure hose. As for the water pump impeller, it is hard to gauge how much sand might have been sucked into the cooling system. One would hope that a small amount of sand might be able to pass through the water pump without causing damage. However, from your data about water pressure decrease and temperature increase, it seems reasonable to conclude that the water pump output volume and pressure are lower than normal, or at least lower than the other motor.
heatxcape	posted 06-01-2010 01:26 PM ET (US) in regard to your reply....(low pressure might also be affected by debris from the sand. Try disconnecting the hose between the motor and the water pressure gauge.) I am not that familiar with the inner workings of the Merc Optimax. Can you advise as to how to find teh hose prior to the water pressure gauge?? anyone happen to have a diagram or good directions?
jimh	posted 06-01-2010 01:40 PM ET (US) You can follow the hose from the gauge, or disconnect it at the gauge.
Tohsgib	posted 06-01-2010 01:55 PM ET (US) Disconnect at the gauge if manual. If electronic then it won't matter. If electronic I might try removing the sensor and see if it had goop in there.
10000 Lakes	posted 06-04-2010 01:05 AM ET (US) Save wondering. Drop both lowers and change out both impellers. Spending eighty bucks and a couple of hours labor could save thousands. Eliminate that first. The fact is common sense here should prevail over mental cures. One engine is running hotter. That says something is amiss for sure besides a tiny water pressure line..