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Jacana · 07-11-2008, 19:18

Hi all and happy and safe sailing.Recently replaced the salt water impeller pump on one motor and have a noticable change in the amount of water and temperature of water coming out . Having twin motors on the cat. at 2500rpms almost half the amount of water is coming out and you cant hold your hand under the water flow as its too hot compared with the other motor.Both engines are running very well and should I be concerned with either one running too hot on discharge or too cold.Thanks Geoff.

Badsanta · 07-11-2008, 20:26

when you changed the impeller, was it complete, any chunks or wear? It may have clogged the heat exchanger causing low flow thus increasing the temp. I have not done it but I think it is just a gasket and a O-ring to take off the end of the heat exchanger to clean and check. Something changed here. Also the exhaust elbow has a tendency to rust and clog if over 3-5 years old. Check that also, it is considered a ware item and needs periodic replacement. Just a thought

Jacana · 07-11-2008, 21:47

Impeller was complete only change was new pump.Thanks Geoff.

Badsanta · 08-11-2008, 12:06

have you checked the exaust elbow?

imagine2frolic · 08-11-2008, 12:14

Something is clogging something. Last June when leaving Florida I had a similiar problem. Turned out barnacles had passed through the pump, and were lodged in the hose on the other side.

RCMURF · 08-11-2008, 12:52

Air bubble?

wsvoboda · 18-12-2008, 20:27

Maybe the belt is not tight enough to rotate the pully for water intake.

Artful Dodger · 19-12-2008, 02:00

Wondering if you have a strainer installed would that not stop the barnacle problem, so the elbow off of the heat exchanger has a problem with rust build up, new one to me, will remove mine and check it out as engine is four years old and have noticed a slow down in water flow but never paid attention to tempersture.

Badsanta · 19-12-2008, 10:16

Yes, the exhaust elbow on the yanmar GM engines is considered a ware item by yanmar and needs to be replaced at times. The easiest way I have found is to remove the 4 mounting bolts. put the elbow and flange on a work bench, apply heat and use several large wrenches. I could not believe how much corrosion was in mine. I could not find the hole with out knocking out the junk with a screw driver. I put on a new one and saved the other.

Jacana · 27-12-2008, 13:32

Pulled heat exchanger out and cleaned no blockages ,pulled exhaust elbow off bit gunky no blockages(hint use 50/50 water and swimming pool acid and soak exhaust elbow for about 10 minutes watch as it eats all the gunk out,dont stand near when putting in water as it can bubble and spurt a bit at first).Measured water output at 2000rpm for 60 seconds then put the old water pump back on measured again guess what the brand new pump only puts out almost half the amount of old pump.After all the f.......g around .....went to visit my trusty yanmar dealer who didnt believe me said he would confer with the workshop guys result they put a new impeller in with twice the amount of blades and should now pump twice as much water.....now its my turn I told him I dont believe him as the only way it can pump more is if it spins faster....soon as I get a chance Ill let you know how the new new pump goes in the meantime a new lesson learnt dont have to have a blockage to effect the water flow.Merry Xmas to all Geoff.