Last week when leaving the dock I checked my coolant water flow at the exhaust, all good on leaving but when motoring out in the Gulf, I noticed the temperature gauge going up and the water had stopped at the outlet. I shut down the motor and on checking the inlet hose after the seacock, found it was plugged with a thick 60cm long seaweed. After removing this and cleaning the water filter just after the hose, the engine ran cool and plenty of water at the exhaust.
I recently changed the water pump impellor, should this be changed again as it ran dry for a spell? The hoses seem fine, any other checks that should be done regarding the overheating? The inlet is just a 20mm hole on the bottom of the boat, would a screen or deflector be a good idea?
The engine is a 3cyl Kabota diesel with a heat heat exchanger.

if 'easy' you can check the impeller to see if it is cooked / burnt / cracked etc....it prob had enough moisture to avoid that as you shut her down..?

The pump would still have enough water in it. Run the engine and hold your fingers on the face plate. If it stays cool your good to go.

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Ramona said..
The pump would still have enough water in it. Run the engine and hold your fingers on the face plate. If it stays cool your good to go.

Excellent tip.. That would save unscrewing 10 fine bronze screws that are usually hard to unscrew,due to seizing..That reminds me, I must replace the screws with the stainless ones I have bought some time ago !!
There is always some to do on a yacht. Lol

The raw water also cools the exhaust hose and water lock muffler if you have one . Check you haven't melted it if it's a plastic one or burned your exhaust hose

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Ramona said..
The pump would still have enough water in it. Run the engine and hold your fingers on the face plate. If it stays cool your good to go.

Not sure I get what you are saying. If the impeller is stuffed and missing vanes it won't pump water but it still shouldnt get hot as it's before the engine and the rubber vanes won't be rubbing against the outside of the housing.

What am I missing?

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Jolene said..
The raw water also cools the exhaust hose and water lock muffler if you have one . Check you haven't melted it if it's a plastic one or burned your exhaust hose

The water flow was fine after he cleaned out the weed. If the muffler melts the water goes into the bilge!

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Not sure I get what you are saying. If the impeller is stuffed and missing vanes it won't pump water but it still shouldnt get hot as it's before the engine and the rubber vanes won't be rubbing against the outside of the housing.

What am I missing?

The seawater temperature off the coast here is very warm at the moment but still far cooler than the engine room temperature. If the pump is working properly the face plate will be cool and sometimes even wet with condensation. If the pump was not pumping the pump body would have the same temperature as the engine block. When you start the engine, by the time you reach down and put your fingers on the face plate your going to know.

Thanks for the replies, the muffler and exhaust hoses seem fine but thanks for the advice, I will have another look at these. There was no indication of water in the bilge. When the motor overheated, a yellow white foam came out of the exhaust for a spell. Unfortunately the water pump is in a terrible spot to work on. I am worried that I could have lost one or more of the rubber impellor fins, which can clog the engine coolant flow if they get stuck in the system. Feeling this as Ramona suggested may still show it working even with the loss of one of the fins?

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Ramona said..

Jolene said..
The raw water also cools the exhaust hose and water lock muffler if you have one . Check you haven't melted it if it's a plastic one or burned your exhaust hose

The water flow was fine after he cleaned out the weed. If the muffler melts the water goes into the bilge!

FFS Just because the water flow is now fine and there is no water in the bilge,,, it doesn't mean you haven't melted plastic or caused damage to the exhaust. The water lock may be still intact but stuffed and destined to fail in immediate future.

So are you saying there is no need to check the exhaust after starving it from cooling water .

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Jolene said..

Ramona said..

Jolene said..
The raw water also cools the exhaust hose and water lock muffler if you have one . Check you haven't melted it if it's a plastic one or burned your exhaust hose

The water flow was fine after he cleaned out the weed. If the muffler melts the water goes into the bilge!

FFS Just because the water flow is now fine and there is no water in the bilge,,, it doesn't mean you haven't melted plastic or caused damage to the exhaust. The water lock may be still intact but stuffed and destined to fail in immediate future.

So are you saying there is no need to check the exhaust after starving it from cooling water .

The question from 2Shakey was, does he he need to check the impeller, as he had just replaced it.
You would think 2Shakey was diligent to check the exhaust hose and box. His concern was the impeller.
So Romona's usual helpful advice is a correct guide.
Additionally, placing your hand on top of the exhaust, will soon tell you if the water pump is working effectively.

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BeamReach said..

Jolene said..

Ramona said..

Jolene said..
The raw water also cools the exhaust hose and water lock muffler if you have one . Check you haven't melted it if it's a plastic one or burned your exhaust hose

The water flow was fine after he cleaned out the weed. If the muffler melts the water goes into the bilge!

FFS Just because the water flow is now fine and there is no water in the bilge,,, it doesn't mean you haven't melted plastic or caused damage to the exhaust. The water lock may be still intact but stuffed and destined to fail in immediate future.

So are you saying there is no need to check the exhaust after starving it from cooling water .

The question from 2Shakey was, does he he need to check the impeller, as he had just replaced it.
You would think 2Shakey was diligent to check the exhaust hose and box. His concern was the impeller.
So Romona's usual helpful advice is a correct guide.
Additionally, placing your hand on top of the exhaust, will soon tell you if the water pump is working effectively.

Why don't you just go and read 2Shakey's original post again.
Specifically the bit that says
"any other checks that should be done regarding the overheating? "