Raw Water Pump Impeller replacement - How to Guide

[SemperFi]

"6.Now comes the hardest part. Loosen the clamps on the intake and exhaust hoses for the raw water pump and remove the hole assembly."

Your not kidding ... For a 240SD an added step to make it 1/10th easier ... Remove the hoses above the Y at the engine block ... This gives you better access to the hoses on the pump so that you can twist to break the seal and then pry gently on both sides of the hose ...

Thanks! ... Your guidance sure saved me a lot of time ...

 

[Suthrn]

Where might one find an impeller kit for a 496? I just got my boat and it's 3 yrs old and I'm sure this hasn't been done. Time to do some preventative maintenance. Thanks.

 

[dstruchen]

Tom,
Do you have a comment on the size of the impeller puller?
Small Impeller Puller for Impeller Size 2-1/4"–2-9/16"
Large Impeller Puller for Impeller Size 3-1/16"–5"

Thanks for the write up!

 

[Presentation]

Tom,
Do you have a comment on the size of the impeller puller?
Small Impeller Puller for Impeller Size 2-1/4"–2-9/16"
Large Impeller Puller for Impeller Size 3-1/16"–5"

Thanks for the write up!

I just did my raw water pump impeller change last night.

With the pump removed, to remove the impeller from the pump I grabbed a impeller fin with a needle nose pliers. With a old t-shirt protecting the insulation on the handle I put the pliers in a bench vice. Holding onto the pump, not the puller, I pulled the impeller out.

To get the new impeller in I put a ty-rap around the impeller, pushed all the fins to they were in the correct orientation, and tightened the tie some more, repeat until the impeller is smaller. If your cable ties are too short you can put one tail thru the next head to make them longer.

Finally, I coat everything with KY jelly, the inside of the pump, the new impeller then push the impeller in the pump assembly.

Pushing the impeller in the pump when I get to the part with the cable tie around the impeller I use a side cutters to cut the tie then shove the impeller in the rest of the way.

 

[shartong]

After the 200 hr service I can no longer flush the Bravo III outdrive out of the water. Water pump cools in the water. Any help would be appreciated. Is it possible the new impeller is too small to draw water up the outdrive when out of the water? Could the new impeller be defective. I checked the belt diagram on the engine and it seems to be running correctly.

 

[Henry Boyd]

I had a similar problem a couple years ago, only mine would stop cooling for no reason while in the water. I replaced the impeller, then the whole pump. In the end I had the yard put a through hull in and seacocks. When they contacted Mercruiser we found out there was a pre-established kit to do just this. My guess is that that the plumbing is just so inefficient that without the hydraulic pressure of the pump being below the water line that lowers the head requirement, the pump can't generate enough suction to pull water up through the muffs.

If you can't find a solution, I'd strongly recommend the through hull pick up. Plus you get the ability to get an in water flushing inlet (at least for the engine).

Henry

 

[widowmaker]

What a great write up! Thanks.
But In 95 heat and humidity I'll give this one to the mechanic.