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Changed the impeller on Merc for the first time & it wasn't easy


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Unlike the vast majority of you with a direct drive, the impeller on my Merc d/d is located halfway down in the engine well. Due to the difficulty getting to the access bolts on the back of the housing, it is necessary to remove the WHOLE unit. Of course to do that I had to first take off the serpentine belt and then bust my hands trying to blindly remove the two hoses conected to the impeller housing (they were on there tight squeazed next to the oil lines and pump). Rant off!

The easiest way to get the old impeller out was not with needle nose pliers but with two long screwdrivers after I put some shaving cream in to assist. I can't see how changing out a v-drive's impeller could be that more difficult than mine. I let mine go for a couple seasons with no visable wear. Needless to say, I won't be changing out my impeller every year!

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I didn't realize Merc was still an option on Bu's. I am with you. I have changed my impeller each spring and none have had any signs of wear and all have been soft and pliable. I think they could go a lot longer than the avg. 75 hour season. But for 30 bucks.......

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I pulled an impeller out of a 4 year old boat that never had the impeller changed and it didn't look bad at all. I think every other year is more than enough, especially if you keep the old one as a spare.

Chris

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I pulled an impeller out of a 4 year old boat that never had the impeller changed and it didn't look bad at all. I think every other year is more than enough, especially if you keep the old one as a spare.

Chris

Unless of course it breaks on the off year. $35 is cheap insurance.

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The trouble that can "potentially" occur with that model of raw water pump (plastic housing type) is the impeller blade can bond (rubber to plastic) together when drained for the winter storage. When I started the engine for the first time during the spring of 2001 even while in the lake the bond was tight enough to tear all the impeller blades off. On the inside of the plastic housing you can also see small slivers of plastic torn off at each place where there was a bond. It tore the impeller all apart.

I now change the impeller each year not so much to replace the impeller (but why not since I have to completely remove the entire pump), but to make sure there is not a bond between materials.

The possible remedy if you don't want this to happen with this particular model is to remove the pump as part of the winterization process and rub a sufficient amount of vegetable oil or equivalent to the inside of the pump housing or what I do since I keep mine in a heated garage is not drain the water from the engine thus keeping the pump housing wet. But now I still go through the process of replacing my impeller each spring just in case or just to inspect the housing.

It sound like an unnecessary pain, but it you can (trust me on this one) have about $5K worth of peace of mind.

IMG_0070_1_1.jpg

Edited by Jesse
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The trouble that can "potentially" occur with that model of raw water pump (plastic housing type) is the impeller blade can bond (rubber to plastic) together when drained for the winter storage. When I started the engine for the first time during the spring of 2001 even while in the lake the bond was tight enough to tear all the impeller blades off. On the inside of the plastic housing you can also see small slivers of plastic torn off at each place where there was a bond. It tore the impeller all apart.

I now change the impeller each year not so much to replace the impeller (but why not since I have to completely remove the entire pump), but to make sure there is not a bond between materials.

The possible remedy if you don't want this to happen with this particular model is to remove the pump as part of the winterization process and rub a sufficient amount of vegetable oil or equivalent to the inside of the pump housing or what I do since I keep mine in a heated garage is not drain the water from the engine thus keeping the pump housing wet. But now I still go through the process of replacing my impeller each spring just in case or just to inspect the housing.

It sound like an unnecessary pain, but it you can (trust me on this one) have about $5K worth of peace of mind.

IMG_0070_1_1.jpg

Your's looks different than mine. My housing appears to be constructed out of brass. I do know that was one of the past problems was that the plastic housing. As a side note you can upgrade all or part of the impeller housing. Of course it's a few $$$. I believe I saw that parts in Overton's. As it is, I'm lucky if I see 60 hours on the bu' with my current work load. I will try the blue "Globe" impeller next change out in a couple of years. During the winter, the engine block (and impeller housing) are full of -100 anti-freeze per owner's manual but still keeping the inside of the housing wet like you do. I believe this should help as well. The impeller that I pulled out after 2 seasons use was almost in mint shape.

I believe that in Mercruiser's zeal to make winterizing as easy as pulling 4 blue plugs, they created another monster with the impeller replacement.

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I tried to replace with the Jabsco brass replacement pump but it would not fit my model of engine. Mercruiser seemed to make a number of changes between 94 and 98 so I can imagine that each year has a something a little different.

Having a brass housing is much better if will fit the engine mount and line up with the pulley belts.

Another problem I had was a year ago while pull the old impeller out I dropped the plastic housing on the concrete and it broke. I had to wait a week for a new housing, but at least it wasn't very expensive.

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I showed a friend of mine at work the housing using Merc's online manual and his response was that was asinine. I then proceeded to tell him that the manufacturer's recommendation was to change it out every year, he replied that he would sell the boat first.

I guess we're just masochists.

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Yeah....the ones that I have pulled out from 2003, 2004, and 2005 have looked like new, but with a close inspection of this year's change the rubber looked a little dry even though I kept the housing wet. I think it could have gone another season, but I had already ordered the replacement.

I can now change mine in less than an hour with totally removing the entire housing from the engine bracket and hoses.

The toughest part is getting the new impeller blades started into the housing. Once I get it started I use the pulley wheel and shaft to push and spin the impeller down into the housing. By using the pulley wheel it is easier to align all the impeller blades in one direction and spin the impeller almost like you are using the wheel and shaft to screw the impeller down into the housing rather than using your hand to push it down.

Edited by Jesse
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  • 2 months later...
The trouble that can "potentially" occur with that model of raw water pump (plastic housing type) is the impeller blade can bond (rubber to plastic) together when drained for the winter storage. When I started the engine for the first time during the spring of 2001 even while in the lake the bond was tight enough to tear all the impeller blades off. On the inside of the plastic housing you can also see small slivers of plastic torn off at each place where there was a bond. It tore the impeller all apart.

I now change the impeller each year not so much to replace the impeller (but why not since I have to completely remove the entire pump), but to make sure there is not a bond between materials.

The possible remedy if you don't want this to happen with this particular model is to remove the pump as part of the winterization process and rub a sufficient amount of vegetable oil or equivalent to the inside of the pump housing or what I do since I keep mine in a heated garage is not drain the water from the engine thus keeping the pump housing wet. But now I still go through the process of replacing my impeller each spring just in case or just to inspect the housing.

It sound like an unnecessary pain, but it you can (trust me on this one) have about $5K worth of peace of mind.

IMG_0070_1_1.jpg

I have just broken my impeller. I have a mercruiser on my 1991 Euro F3. It is V Belt attached. We had been in the water 2 times a week since mid march. During July we went to Minnesota for vacation and left the boat in the driveway. When we got back we went to the lake as soon as we could. The engine would not crank and then I heard a big pop. Not knowing what it was, I surveyed the engine and all the belts looked okay. Then I noticed the engine temp was creeping up. WE drove it out on the water and it cooled down until we slowed to an idle again. Then the water temp went back up.

I check the intake the water was coming in the hose just fine. We then went back home (no skiing that day *sniff*). I took the water pump off and all of the blads on the impeller were shredded off and stuffed into the inlets for the water.

Now for my question....... What can I do to avoid the impeller drying out and adhereing to the plastic housing? I have never known I should replace it every spring, but I think that is good advice. What if I am gone next summer for a month again? What measures should I go to to prevent the impeller drying out or causing problems from lack of use? Should I run some water into the engine to keep it moist?

Sorry for such a long winded note. I have ordered the mercruiser replacement from SKIDIM and I hope it fits now after seeing some of these posts. Where is a good place to get a replacement impeller?

Thanks for your patience for reading all of my ramblings.

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