Hi all

Had a great sail yesterday off Mooloolaba with my brother and niece - even sailed back into the river through the bar. Started the engine in the river to pick up some non-sailors for a BBQ and no water coming through the exhaust. Pretty sure it was initially but after 20 mins or so noticed temp too high and no water coming out.

Turned the engine off and sailed into the pond near Lawries. Then turned it on to get into berth without any problems.

Spent a couple of hours today checking the impeller - looks OK - and the intake also looks OK. Pulled impeller out and reinstalled. Still no water.

Have had problems about 3 years ago when it seemed the pump didn't like getting air locks. Seemed to stop pumping after sailing if I left the intake through hull open. So now I close everything up when the engine gets turned off.

Any ideas welcome!

Scott

Check the exhaust elbow, I had a similar problem a few years back
The elbow can corroded and block the flow of water out of the wet exhaust.

You can check by connecting a length of hose to the pipe that leads to the exhaust elbow and run the hose into a bucket. Start the motor and if you get water into the bucket if confirms the problem is in the elbow.

What motor is it?

Is your sea strainer hogh above the water line
In my old boat the priginal sea strainer was well above the wayer line
So in some situations it could drain back causing an air lock
Ive since moved it and lowered its position so now sea water level is near the top of the strainer lid
Also some time small fish can get stuck in the hose coming from the hull through hose going to the pump
Im not sure what motor you have the buhk i have has a chain drive spinning the pump sharf

Hi, same as your problem I'd solved by driling fiev holes in the front of raw water intake housing.This eliminated venturi efect. Before that pump was sucking cooling water trough slots on the back of the skin fitting, but during sailing with motor stoped venturi efect sucked/dryed system due to pump impeler wear.

Is it possible the rubber impeller is spinning on the bronze hub. I've seen this before. It still looks visually okay but doesn't have the traction to pump water.

The impeller is probably fine but check the wear on the face plate. Once a groove appears the pump will often not prime. Tolerances are critical here and ensure you use a gasket. Arrange the water intake and outlet hose to the pump so that some water always lays in the pump when its not running. Smear a bit of grease on the impeller and face plate for the start after pulling it down. Put your finger on the face plate while the engine is running, it should always feel cold.

I agree Ramona. And I was told always to coat the impeller with vaseline before assembly.

You can refinish the face plate, removing wear marks and grooves. Use wet and dry sandpaper on a flat surface like a sheet of glass or ply. Takes a while!

The back plate also wears. It depends on the pump design whether you can do anything about this. However the point will come eventually when you're better off to buy a new pump or refurb kit. All the priming problems will then go away for a few years.

Thanks all

The motor is a 23HP Kubota and is probably as old as the boat so 27 years. Will check the exhaust elbow. The face plate is a little worn. From memory the mechanic last time put ?locktite on it to help with this. The filter is below water line so that should be OK.

Refurb or replace the pump is my suggestion. Loctite won't help.

Start at the water inlet. Are you getting water past the seacock? These things can get crusted up inside and need cleaning out.

Hi papabear,
I spent a lot of time with your type of raw water pump problem - turned out to be the heat exchanger almost entirely blocked by sea grass ( strands about 100mm long, 3mm wide).
While most of this stuff was caught by the filter, small amounts accumulated over time at the inlet to the heat exchanger.
Fixed the problem permanently by adding a finer secondary filter after cleaning out the heat exchanger.
regards,
Allan

Select to expand quote

Datawiz said..
Hi papabear,
I spent a lot of time with your type of raw water pump problem - turned out to be the heat exchanger almost entirely blocked by sea grass ( strands about 100mm long, 3mm wide).
While most of this stuff was caught by the filter, small amounts accumulated over time at the inlet to the heat exchanger.
Fixed the problem permanently by adding a finer secondary filter after cleaning out the heat exchanger.
regards,
Allan

Any potential problem with the finer filter clogging and stopping water flow altogether Allan.??

Select to expand quote

samsturdy said..

Datawiz said..
Hi papabear,
I spent a lot of time with your type of raw water pump problem - turned out to be the heat exchanger almost entirely blocked by sea grass ( strands about 100mm long, 3mm wide).
While most of this stuff was caught by the filter, small amounts accumulated over time at the inlet to the heat exchanger.
Fixed the problem permanently by adding a finer secondary filter after cleaning out the heat exchanger.
regards,
Allan

Any potential problem with the finer filter clogging and stopping water flow altogether Allan.??

No Sam,
The primary filter captures almost all of the seagrass - it's mostly short pieces (less than, say, 10mm) that the secondary filter captures. By themselves, these short pieces wouldn't accumulate in the heat exchanger - it's the occasional long piece that gets through the primary filter that can initiate the 'log jam' in the heat exchanger.
Its capturing these ones that makes the secondary filter is so worthwhile.
In practice, I have to clean the primary filter at least 10 times more often than the secondary.
regards
Allan

Talking about pumps I came across this bad boy the other day I intend to get one to circulate my hot water system, one moving part and its water proof

some were replaced under warranty

lusciousgarage.com/blog/prius_inverter_water_pump_recall_c0u_-_details_for_owners/

Select to expand quote

Datawiz said..

samsturdy said..

Datawiz said..
Hi papabear,
I spent a lot of time with your type of raw water pump problem - turned out to be the heat exchanger almost entirely blocked by sea grass ( strands about 100mm long, 3mm wide).
While most of this stuff was caught by the filter, small amounts accumulated over time at the inlet to the heat exchanger.
Fixed the problem permanently by adding a finer secondary filter after cleaning out the heat exchanger.
regards,
Allan

Any potential problem with the finer filter clogging and stopping water flow altogether Allan.??

No Sam,
The primary filter captures almost all of the seagrass - it's mostly short pieces (less than, say, 10mm) that the secondary filter captures. By themselves, these short pieces wouldn't accumulate in the heat exchanger - it's the occasional long piece that gets through the primary filter that can initiate the 'log jam' in the heat exchanger.
Its capturing these ones that makes the secondary filter is so worthwhile.
In practice, I have to clean the primary filter at least 10 times more often than the secondary.
regards
Allan

Good Al......I know seagrass can be a problem. I have a mate on the Central Coast NSW who fishes on Brisbane Water.
He gets seagrass wrapped around his prop and has to reverse to unwind it because it slows him down......annoying.