Mercruiser 470 water pump

[arnettmark]

Getting back into boating after 15 years, I bought a 1979 SeaRay with a Mercruiser 470. While tuning up the carb, the barrel of water the outdrive was in tipped a little and exposed the impeller intake (without my noticing!). Before long, the outdrive was smoking. I assume the water pump melted down and will need to be replaced, but what else should I inspect/replace when doing the water pump?

I'm also upgrading to a 4" heat exchanger, anything else I should tackle while I am going through this cooling system?

[HT32BSX115]

Howdy,

Yes, you'll be replacing the whole pump, housing etc.....

Since you're replacing the heat exchanger, you probably don't need to flush your 3" one of the fragments that could have gotten into it....

If you have a power steering or engine oil cooler, look at the raw water path to them (and in them) for impeller fragments and other debris etc...


Regards,


Rick

[stonyloam]

I would pull the whole outdrive, and check the gimbal bearing and u joints. Also check the condition of the bellows. It is a lot easier to do the impeller with the outdrive off anyway. As I understand it, if you are using a tank you need to have the water level above the level of the impeller housing, not just above the level of the intake, so it is better to use a hose and muffs if you can. The 4" exchanger is a fine idea.

[EddiePetty]

...and while you have the complete outdrive off, peek up into the exhaust passages for the remains of a former flapper (shutter) valve.
And, just for grins while you are removing the undersized 3" heat exchanger, remove the forward end plate of the exchanger and see how many impeller pieces are lodged there.
When I upgraded to the 4" exchanger I replaced the water supply hose from the inboard transom nipple to the exchanger with clear, nylon reinforced tubing to permit me to monitor water supply with the doghouse open. Really comes in handy on muffs as you can see the moment the impeller becomes water starved by engine speed. Underway, the clear tube is the first thing I check should I get an over-heat indication. Additionally, I check my water supply everytime I launch...just habit now.