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1992 3.0 liter Raw Water pump issue

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Kmoore37

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New to boating and this forum...Brought boat home from saltwater lake ( after running for 2.5 hours with temps around 165 at all speeds)put muffs on to clear salt water from system. Never got water flow out of the exhaust (only ran at idle for 8 seconds) shut it down and found impeller housing somewhat deformed (from heat) the impeller was also somewhat damaged. This impeller and housing (sierra) had about 75 hours of run time over the course of a year. I replaced the housing and impeller and still do not get water flow out of the exhaust UNLESS I firmly hold the muffs againist the intakes to ensure no leakage and pressure feeding the raw water pump. Took boat to lake and still do not get and flow thru engine. I believe since the first pump overheated I think it was not able to suck in water as it should. Bottom line....the raw water pump is not drawing water from the lake or with muffs...they only way it will work is to Pressure feed....Any ideas???
 
I would remove the Impeller and Housing and if you have power steering(probably not on a 3.0L) you'll need to check the power steering cooler at the back of the engine (usually) for peices from the impeller. Check the condition of the water hose at the outdrive, clamps tight? Hose good? You'll also want to disconnect the water hose where is goes into the Thermostat housing and back-flush with a garden hose ( use a clamp ). Then I'd take a look at the Thermostat housing they can get clogged up too.. then, I'd Feed water directly into the Intake/Exhaust Manifold and see what the flow looks like coming out.. you may have blockages in the Manifold and Elbow, too.. .very typical with age and even more with Salt Water use.
 
Check the tube and many grommets/seals from the suction side of the impeller down to the "water passage housing" for integrity. There's a gasket under that housing as well on top of the lower unit.
 
I know my post was long and could be confusing...In short I do have normal flow thru the engine and out of the exhaust ONLY when i tightly hold the muffs to the water intake on the foot. It wont suction feed when in the water or just with muffs on....i am stumped???
 
Kmoore37 said:
I know my post was long and could be confusing...
Click to expand...
mine was short and concise, but I'll make it longer....

Cobras are great for having the water pump up high, but it means the suction tube has to run down to a housing that basically fits where the pump would be on a Johnson/Evinrude lower unit. The soft seals and grommets on the tube don't generally seal well for 21+years.

When you clamp your ear muffs on there- the leaks are less of an issue because of the sheer volume of water.

of course - that's just one possibility that has to be explored.
 
Ok I understand now..Thanks... and I think you are right! The housing and impeller I installed last year toasted because it was not getting enough water but enough water to keep engine temp down, so I knew nothing about it till I got home to flush it out. OK, is there anyway to get to the suction tube without removing the upper and lower sections?
 
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