How often should impeller be changed?

[mercibby]

Re: How often should impeller be changed?

Hi All -

I've heard that the impeller should be changed every other year (Merc. 3.0 L w/Alpha I Outdrive in fresh water). How true is this?

The reason I ask is because it's going on the "every other year" for my boat. I changed it when I first purchased it used--the owner told me that the impeller hadn't been changed for at least three years. When I looked at the old one, it appeared to be in good condition. I changed it anyways.

What is a good rule of thumb?

Thanks for any advice!
d

mercury wants you to check the impeller every 100 hours but if you are going to take the time to pull the lower off and check the impeller than you might as well change it while your in there. Working at a marina in iowa we always tell our customers as a good rule of thumb that they should change there impeller every 3 years under normal operating conditions.

 

[MrBill]

Re: How often should impeller be changed?

It is most critical that the impeller (raw water pump) be in optimal condition in closed cooling systems. All 3.7L Mercruiser engines had closed cooling systems, other engine models were optional. In closed systems, this is the only mechanism pumping cool, raw water into the heat exchanger. If it is in less-than-good condition, the engine temp will rise significantly, particularly at WOT. While on muffs the engine will operate normally because the supplied water pressure will flow through the impeller and not be a good indicator of its true condition.

Its an easy job...in my 3.7L, I replace the impeller ($10) every other year, and the entire pump assembly ($35)every fourth year. Been doing this since 1989...the engines been perfect, and in a 3.7L that's a feat. One overheat and your engine could be toast.

 

[marinemech1]

Re: How often should impeller be changed?

if its in your hand replace it
if you want to check pump performance they used to give specs in service manuals (they still might)
it was i think 6" water out of hose if engine at idle and hose held ? inches above static water line

 

[JoChek219]

Re: How often should impeller be changed?

Hey Mr. Bill, I was just wondering where do you get your parts, I also have a 3.7...1987 this upcoming season will be my 2nd season with the boat and was thinking of maybe replacing imperller just to know its new and in good shape. Was also wondering how hard is it to replace the entire pump assembly

 

[andy1canada]

Re: How often should impeller be changed?


Howdy from Victoria BC Canada!

Just thought I'd jump in and let you and Mr. Bill know - if you don't already - about a great connection for all 470' Merc. owners. (I have one in an older boat that I'm in the process of selling because I've bought another boat)

The site is called Breezeworks (Google it) and the fellow that runs it out of Florida lists parts for the 470 - many hard to one's... like 4-BBL intakes, 4" heat exchangers etc. - and there's also a link to a Forum (chat) that's chaulk-full of 470' owners who discuss everything from alternator-conversions to - how to stop your beer from fizzing at 50 mph.

It's a very useful and fun forum.

Hope it helps!

Cheers,
Terry

Victoria, BC

 

[imported_boatin clan]

Re: How often should impeller be changed?

I have my impeller changed every other year wether it need it or not. Best to remove the lower unit periodically than to have it get stuck and have to heat it with a torch to remove it. Like Mr. Goodwrench used to say "You can pay me now or pay me later"