Originally Posted by johnnyq
I tried to bypass the switch but no joy. Impeller is replaced, coolant checked, strainer clean, thru hull
clear, any other suggestions?
If that unit is a pressure switch then I guess it must work
like the oil
sensor switch as well. The pressure switch is after the saltwater pump
so the pressure should be anything from 10 psi to 40 psi. From boatdiesel, clark leighs talks about the installing a pressure meter which is a good idea to compare the readings when your lco alert comes on. He goes to even put the pressure gauge before raw water pump
to isolate the problem. I think that is a great suggestion.
You did not mention about swapping to a new pressure sensor yet so I assume the parts
have not arrived yet.
There are 2 possibility here:-
1. The pressure switch faulty from day 1 . So changing out the part could solve the problem - easy test.
2. The pressure switch is not faulty. Then this present another set of things to check off. I am simply listing items I would go through
- intake thru hull
, clogged, parts
- sea cock is faulty , not fully open even the lever is fully open.
- the hose may looks fine but the inner tube has collapsed. A visual check or simply just replace it.
- sea strainer is clogged, sea weed etc
- raw water pump
, impeller (which you have replaced), could be air leak, worn out face plate, bad rubber gasket
, (will seal well when engine
is cold), seals
(have to remove the whole unit),
- hose clamps , cracks on the hose allowing air to get in,
- some people replace the impeller pump with March pump (need to check the output and ensure the March pump is below water line as it cannot self prime)
- use a IR heat temp with laser to take the readings for your raw water pump
to see what is the reading when LOC shows up. May be heat related.
- take out the heat exchanger
for service/cleaning and do a pressure test
- same time take out the elbow
and check for clogging. May be the back pressure from the elbow
or heat exchanger
is causing the LOC.
Good luck johnnyq