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Old 06-19-2013, 08:02 PM
NotEnoughTime NotEnoughTime is offline
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Johnson Raw Water Pump Cover Plate blew off

I took my boat out after de-winterizing and about 40 minutes into the trip we started losing power and noticed there was more exhaust than normal coming from the back of the boat. We killed the engine immediately and opened the back hatch. I saw water pouring out of the water pump housing. The cover plate was on the floor with the screws next to it. I know for sure that I tightened those screws when I replaced the impellar just a few days prior.

I have attached some pictures of the pump and the screws. You can see on the screws that some of the threads are messed up. I'm sure the threads were fine when I put the cover back on. So the threads must have gotten messed up when the cover plate blew off.

I was thinking about just getting new screws and running the boat while keeping a close eye on the housing and see if that resolves it. At first I figured if the screw threads were damaged the female threads on the housing must be damaged, but they seem fine.

I have owned the boat 4 years and changed the impellar every year, nothing like that has ever happened before.

My thought is that maybe I over-tightened the screws?

Has anyone ever seen this before? Any idea how this could have happened? Could it be from over-tightening?
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Old 06-19-2013, 08:06 PM
snork snork is offline
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over tighten the screws, put a new impeller in and keep the old for a spare
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Old 06-19-2013, 08:06 PM
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mikeg205 mikeg205 is offline
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Screws over tightened stripped out... pump threads look ok
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Old 06-19-2013, 08:59 PM
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ricford ricford is offline
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Is that the right impeller? There are two lengths apparently. The last picture looks like it's sticking up a bit from the housing. I've heard of guys putting the short one into a long pump and having no suction. I wonder if putting the long one in a short pump would strip the screws out.
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Old 06-20-2013, 08:42 AM
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Rossterman Rossterman is offline
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Pull the impeller and measure the depth of the housing. Should be 1 7/8 or 2 inch. Verify you have the correct impeller length. Most M/Cs have the 2 inch pump and problems come when the install the shorter impeller but you could have the opposite issue.
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Old 06-20-2013, 09:32 AM
NotEnoughTime NotEnoughTime is offline
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The impellar was sticking out from when it was on the engine. Once the cover blew off the impeller was working it's way out of the housing. I pushed it back and it's now sitting flush.

Can I get replacement screws at the hardware store? Or do I need to order special ones for this housing?
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Old 06-20-2013, 09:41 AM
bigmac bigmac is offline
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Quote:
Originally Posted by NotEnoughTime View Post
The impellar was sticking out from when it was on the engine. Once the cover blew off the impeller was working it's way out of the housing. I pushed it back and it's now sitting flush.

Can I get replacement screws at the hardware store? Or do I need to order special ones for this housing?
They're brass. Steel would strip the $200 pump housing instead of a $2 screw.

http://www.skidim.com/prodinfo.asp?number=68-5005
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Old 06-20-2013, 10:18 AM
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In the last pic, it looks like the impeller is a little long for the housing.
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Old 06-20-2013, 02:52 PM
FrankSchwab FrankSchwab is offline
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Those don't look like brass screws - and they don't look like the ones (either originals or replacements) on my pump. Are you sure that they're the right material and size?

The stripped threads on the screws are weird - note that the end of the screw that's deepest in the body is perfectly fine, and the stripped part is in the middle of the threads? In my experience, overtightening will break the screws before it strips the threads, and in any case overtightening that stripped the threads would strip them all the way to the end of the screw. I'm thinking that you DIDN'T tighten the screws, they started backing out, the cover plate started moving around (wearing the middle of the threads), and eventually the screws backed all the way out.
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Old 06-20-2013, 03:31 PM
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Quote:
Originally Posted by FrankSchwab View Post
Those don't look like brass screws - and they don't look like the ones (either originals or replacements) on my pump. Are you sure that they're the right material and size?

The stripped threads on the screws are weird - note that the end of the screw that's deepest in the body is perfectly fine, and the stripped part is in the middle of the threads? In my experience, overtightening will break the screws before it strips the threads, and in any case overtightening that stripped the threads would strip them all the way to the end of the screw. I'm thinking that you DIDN'T tighten the screws, they started backing out, the cover plate started moving around (wearing the middle of the threads), and eventually the screws backed all the way out.
I was wondering the same thing about the stripped threads only in the middle. I like your explanation.
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