496 Mercruiser HO impeller water pump change

[Hatchman]

Hello, need some help please. Boat is a 2005 Sea Ray SLX 270 with Mercruiser 496 HO 425hp and Bravo 3 and boat also has fresh water /antifreeze cooling.

Tried to start the boat yesterday. Water pressure showed .6 psi while on the hose, so shut it down and put it in water to see if that would help, water pressure was only 1.0 and got an engine alarm. All Smartcraft gauge info showed engine OK, temp OK, oil temp OK, oil pressure OK, basically all the gauges were OK except for the alarm.. Shut it down raise the hatch and seems the exhaust was pretty hot, so the alarm was probably due to the exhaust temp sensor. Hopefully shut it down before any exhaust damage.

Do you think it is the impeller? What is the part number Good place to buy it?

EDIT: Engine Serial number is OW345078 and think I found the part number for the impeller

Mercruiser Brass Sea Water Pump Impeller
PRICE: $28.91
Part #: 47-862232A 2

And housing if it is scored:
HOUSING-IMPELLER (#46-862914A13)
PRICE: $249.91
Part #: 46-862914A13

Would it be better to change out the whole sea water pump? Part number?
How hard is it to get to and how long should it take, what tools will I need?

Marine quoted 600 bucks to change out the impeller and an extra 750 if it required the entire sea water pump and extra on top of that if the heat exchanger had to be back flushed to get out impeller bits, so this could run over 1500 for replacing a 35 dollar part. Sound high?

Thank you for the advice! My search skills are killing me, when I try to search for info I get 500 threads, and they seem to only have one word I am searching for and not sure if the parts I am finding online are right for this boat.

Thank you for the help!

 

[dubs283]

Re: 496 Mercruiser HO impeller water pump change

as with any overheat situation, the first place to look is the impeller

you more than likely have the newer style brass pump, you shouldnt have to replace it unless the bearings/seals have gone out on the shaft

you definitely need to find all impeller pieces if any hsve broken off

check the diy section for mercruiser manuals, follow the links for your specific engine and get the manual for your engine

dunno about parts numbers, etc...pretty easy to find things here on iboats or the www

 

[Don S]

Re: 496 Mercruiser HO impeller water pump change

The impeller is the first thing to change, and should be replaced at least every other year.

Do you have a serial number handy? Not really any way to look up parts by year of your boat, and the engine may be a year older or newer than the boat.

 

[Hatchman]

Re: 496 Mercruiser HO impeller water pump change

as with any overheat situation, the first place to look is the impeller

you more than likely have the newer style brass pump, you shouldnt have to replace it unless the bearings/seals have gone out on the shaft

you definitely need to find all impeller pieces if any hsve broken off

check the diy section for mercruiser manuals, follow the links for your specific engine and get the manual for your engine

dunno about parts numbers, etc...pretty easy to find things here on iboats or the www

Thank you for the info! Did a search and think I found the part numbers. Will look for the manuals. Thank you!

The impeller is the first thing to change, and should be replaced at least every other year.

Do you have a serial number handy? Not really any way to look up parts by year of your boat, and the engine may be a year older or newer than the boat.

Yes, found the serial number and think I found the right part numbers. Thank you!

 

[Don S]

Re: 496 Mercruiser HO impeller water pump change

Replace the seal ring as well. #3 in the picture below.

Would it be better to change out the whole sea water pump? Part number?

That depends on the condition of the other parts. There will always be some wavyness of the impeller surfaces, it's when they become excessive they become a problem.

How hard is it to get to and how long should it take, what tools will I need?

I had one boat that I had to pull the engine out of to change that impeller, so it all depends on how your boat is setup. No one can tell you how long. The tools needed is whatever it takes to do the job.

 

[Hatchman]

Re: 496 Mercruiser HO impeller water pump change

Thank you all for the info.

Doing more searching around, it seems the best way is to take off the idler pulley and then take off three bolts and unbolt the whole seawater bracket from the engine. There should be a water pressure sensor to disconnect, and the two large water hoses from the rear held on with screw clamps.

Looks like tools will be a 10 mm socket or wrench, 6 mm socket or wrench, flat head screwdriver, and assorted extensions, drivers, etc.

I don't think I will have to pull the motor, but you never know! Waiting for the impeller to come in. The impeller comes with the O'ring/seal, so that will be replaced as well. Don't plan on replacing the housing (another 300) unless it is gouged.

Will report back with results. Thank you for all the info!

 

[Hatchman]

Re: 496 Mercruiser HO impeller water pump change

Replaced the water pump impeller, no change. Looked like it had a little scoring on the cover plate.

Thinking of trying this next:
Mercruiser Seawater Raw Water Pump SS Wearplate Repair Kit BRAVO3 | eBay

The 2.5 year old impeller was frozen in the curled position, the blades were not even touch the sides of the housing on one side. The complete impeller was there, no pieces missing / broken.

Water pump was still full of pink antifreeze, which means during the minute or so the engine ran, the water did not circulate anywhere.

Even with new impeller, still no circulation. Thinking it is either a blocked heat exchanger or scored water pump.

 

[Bondo]

Re: 496 Mercruiser HO impeller water pump change

Replaced the water pump impeller, no change. Looked like it had a little scoring on the cover plate.

Thinking of trying this next:
Mercruiser Seawater Raw Water Pump SS Wearplate Repair Kit BRAVO3 | eBay

The 2.5 year old impeller was frozen in the curled position, the blades were not even touch the sides of the housing on one side. The complete impeller was there, no pieces missing / broken.

Water pump was still full of pink antifreeze, which means during the minute or so the engine ran, the water did not circulate anywhere.

Even with new impeller, still no circulation. Thinking it is either a blocked heat exchanger or scored water pump.

Ayuh,... It could be a plugged heat exchanger, but more than likely the scorin' in the pump is the problem...

 

[Hatchman]

Re: 496 Mercruiser HO impeller water pump change

It was the scoring. A rebuild kit with stainless steel plates fixed it right up. Now that I know how to do it, it was much quicker to swap it out, 18 minutes to get it off, 22 to put it back on (including the serpentine belt). Marina wanted to charge 6 hours labor for an impeller change...