Sea Water Pump pulling water?

[jbutler67]

Rampage 24 Express
Closed cooling system
Mercruiser M048938

Is there any way to test the Sea Water Pump is pulling water? If engine is run for 30 seconds on land, will it drain any water in the sea strainer? (I'm hesitant to run dry... don't want to damage the impeller in the sea water pump.)

When I run it on a hose, the engine stays nice and cool - around 160-165 degrees. Took it out on the water for the first time today, it got above 225 degrees and climbing before I shut it down.

The seacock to the sea strainer was definitely open.

I'm wondering if it stayed cool on hose because hose was forcing water?

Tomorrow, I start diagnosing the overheat problem. Any pointers greatly appreciated.

Thanks!

 

[jbutler67]

Follow up....

This may be a stupid idea, but please tell me if it is.

Can I take the cap off the sea strainer and keep filling it with water while engine is running... to test the Sea Water Pump?

 

[Palone]

Over flowing the sea strainer is not recommended because water is not drawn from the bottom of the strainer.. Your first instinct is correct. The garden hose pressure does help aid the sea pump.I think you have a weak impeller or an obstruction somewhere.

 

[harringtondav]

Over flowing the sea strainer is not recommended because water is not drawn from the bottom of the strainer.. Your first instinct is correct. The garden hose pressure does help aid the sea pump.I think you have a weak impeller or an obstruction somewhere.

Yes. My experience with full inboards is w/my bud's 42' Bluewater. If your strainer is and hull grate are clean, it's probably the impeller. He has twin 350s and a Kohler generator. Seems he's changing an impeller somewhere every 2 yrs. He keeps a stack of spares in his cabin.

Edit: Be sure your strainer gasket is good, and installed tightly. Leaks here will draw air, and cause overheating.

 

[achris]

Put a section of clear hose in the line. You'll see if it's dragging water in, and if any air's getting into the system too.

Chris.....

 

[Scott Danforth]

raw water pumps dont draw water, they push water.

they need to be flooded to prime. in boats, this is done at rest by the fact that the boat sea water pump is installed below the water line

as the boat gets moving, the pickup helps force water to the impeller

if you overheat in water, and not on the hose, change the impeller.

 

[jbutler67]

Pulled the Sea Water Pump today. Problem was definitely the impeller! It stayed cool on hose because hose was forcing water. But the impeller had seen better days! (pics attached)

Lesson learned... be careful doing a test on the hose!

I spent 25% of the day pulling the Sea Water Pump and the other 75% of the day back flushing hoses to get rid of all the little impeller parts.

 

[Scott Danforth]

Now celebrate during the last part of the day with the spirit of your choice

 

[tank1949]

Rampage 24 Express
Closed cooling system
Mercruiser M048938

Is there any way to test the Sea Water Pump is pulling water? If engine is run for 30 seconds on land, will it drain any water in the sea strainer? (I'm hesitant to run dry... don't want to damage the impeller in the sea water pump.)

When I run it on a hose, the engine stays nice and cool - around 160-165 degrees. Took it out on the water for the first time today, it got above 225 degrees and climbing before I shut it down.

The seacock to the sea strainer was definitely open.

I'm wondering if it stayed cool on hose because hose was forcing water?

Tomorrow, I start diagnosing the overheat problem. Any pointers greatly appreciated.

Thanks!

With boat in water and at idle disconnect output water hose at riser for a MOMENT. See if lots of water is pumping. Or, replace impeller or buy a digital inferred thermometer and compare. They are cheap at Harbor Freight. I have one in my boat. Take out the "stat" and compare degrees. U may have a stat going bad too!