454 7.4 mpi l VI sea pump back flush question and help please
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454 7.4 mpi l VI sea pump back flush question and help please
Hey guys I have a 99 boss 302 with twin 454 7.4 mpi VI models with around 144 hours... Both engines have ran good around 4-5 times with no issues but today my star board engine started to run hot( prior to this temps seemed up and down, I had the beeper come on today... I noticed one engine pissing out both exhaust pipes and the engine which got hot only pissing out of one exhaust very little... I'm pretty sure it's prob my sea pumps so I have new one the way!!!! Do you all agree on that??? Also when I replace my sea pump impellers should i back flush my raw water cooling system? If so how do I do it please???
#7
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If your motor is the same as mine, water flow comes from transom assembly to seawater pump , then under the motor and into 2 colors on the other side along the oilpan, then at the front of the motor it makes a 90 straight up thru another cooler then the thermostat housing. When I flushed mine I separated the hose between the last cooler and the motor. backflushing from here and separating each cooler will usually get all the chunks. If your overheating only on one side, if you have something plugging it up it will be further down stream since the separation side to side doesn't start until the thermostat house. try pulling the thermostat so you get good flow thru the block.head, and disconnecting the hose that goes from the motor to the exhaust manifold and backflush from there. pull the drainplug on the boat and pay attention to the water level in the bilge as it can rise pretty quick.
#9
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If you don't have strainers you could have sucked something up. No you don't have to flush it, you just have to be willing to buy a new motor if you cook this one because you didn't. So if your motor is worth less than 45 minutes of your time and a new thermostat gasket by all means skip flushing it.