Totally confused!!!

Chemdawg

Petty Officer 2nd Class
Joined
Aug 31, 2013
Messages
112
Hello everyone. Hoping someone here has seen this before and can pitch me some intel. I have the 3.0 mercruiser 4 cylinder. Went through everything, and the motor runs great. I had realized that It was getting a bit on the hot side, so I shut it down before It got too hot. I decided to check out the lower end water impeller since I didn't know the last time it was replaced.

Wow, what a mess. It was completely melted, and the upper housing was pretty messed up with all the burnt rubber. So I spent 110 bucks and bought the lower housing, upper housing, gaskets, impeller, and oil and all that stuff. Rebuilt the whole thing, and started it, and it ran great.

I rewired everything this last week, and today I went to start it again, and realized it wasn't pumping water again. Pulled off the hose that goes to the thermostat housing from the lower unit, and saw I wasn't getting any water. Put my rabbit ears on instead of using the 30 gallon tub that I normally use, and tried to force water up there, and NOTHING. So I decided since it was easy enough to do, I pulled the lower end off again, connected the rabbit ears, and turned on the water to see if it would come out the tube. NOTHING. So now I pulled off the housing for the water impeller again, and it was totally burnt to a pulp again.

I am totally confused how this could happen when everything was brand new, and was ran for maybe 15 minutes total.

Now here is how it went together. Gasket-lower housing-gasket-metal plate-gasket-impeller in housing-housing, with of course the key in there. I know it should have been together correctly, since it was pumping water the first time I put it in, and I got the assembly print from my boat shop.

So how could this have burnt out so fast? Ideas?
 

achris

More fish than mountain goat
Joined
May 19, 2004
Messages
27,468
Re: Totally confused!!!

What sort of engine speed were you running on the hose?

Did you check that the water intakes are clear?
 
Last edited:

littlebookworm

Chief Petty Officer
Joined
Nov 30, 2007
Messages
574
Re: Totally confused!!!

You son't say which outdrive you have, but I'll assume you have an Alpha. You really should list the engine and drive serial numbers and types. Have you checked that the vertical shaft is locked in place so that the gears at the top turn the shaft as the engine turns the drive? It sounds to me that the drive shaft is falling down, which, in turn, does not turn the water pump. I suggest you first download a manual for the drive and look at the breakdown photo of how everything goes together. Then check the vertical shaft. Hope this helps. Hy
 

achris

More fish than mountain goat
Joined
May 19, 2004
Messages
27,468
Re: Totally confused!!!

.... I pulled off the housing for the water impeller again, and it was totally burnt to a pulp again. ...

This indicates a lack of supply water. Only takes about 60 seconds to make an impeller crispy fried. When you run in the '30 gallon tub', the water level is ALWAYS above the anti-cav plate, yes?

Chris.......
 

Chemdawg

Petty Officer 2nd Class
Joined
Aug 31, 2013
Messages
112
Re: Totally confused!!!

Sorry about the lack of info. I have a 3.0L mercruiser with the alpha one drive. No numbers off hand right now. Now that i'm really thinking about it, I'm wondering if I really did cause this. Like I said, I rewired everything from the motor harness forward. During that time, I had to turn the motor over several times to check the ignition switch wiring. That's one time I could have helped burn it. I also started it once and shut it down to make sure it started..... Another time I probably assisted in burning it out.

When I run the motor, I use the 30 gallon tub and lower the motor till the intake fins are all the way under. Now one thing someone told me, was that I should use my rabbit ears to start pumping the water, then submerse it under water before I start it. Is this a true statement?

Now I'm going to replace the impeller here, but I'm wondering about the housing. Can I just scotch brite it clean, or do I need to buy a new one. I watched videos where guys cleaned them up with scotch brite and mild emery cloth.
 

thumpar

Admiral
Joined
Jun 21, 2007
Messages
6,138
Re: Totally confused!!!

How high is the water level in your 30 gallon tub? The water needs to be up to the impeller level in a tub like that to work. I would bet that the water was not high enough and you just burnt up the second impeller. Muffs work because they push water in and up to the impeller.
 

Scott Danforth

Grumpy Vintage Moderator still playing with boats
Staff member
Joined
Jul 23, 2011
Messages
47,309
Re: Totally confused!!!

also, never run more than 1000 rpm on muffs
 

Chemdawg

Petty Officer 2nd Class
Joined
Aug 31, 2013
Messages
112
Re: Totally confused!!!

I think your right thumpar. The tub is like the perfect depth for it. The intake fins on the lower end are completely submersed under the water. The muffs are going to be my best bet from this point on, because I don't want to take the chance of starting it dry.

So what do you think about the impeller housing? Think it's ok to just clean it up?
 

Chemdawg

Petty Officer 2nd Class
Joined
Aug 31, 2013
Messages
112
Re: Totally confused!!!

Now that I know I have a problem, I think I'm going to go ahead and replace the whole thing again. Here are the numbers that were on my motor:

B523519 Motor
C3575167 Transom
0B560715 Drive Unit

It is an Alpha One drive. I looked at the parts on this site, and I found a kit that looks just like what I have. However, I want to verify with someone here that this is the correct one according to my numbers. Here is the link

Water Pump Kit for Mercruiser 46-96148A8 46-44292A5 46-44292A3, GLM 12120 - Sierra 18-3320 - iboats
 

achris

More fish than mountain goat
Joined
May 19, 2004
Messages
27,468
Re: Totally confused!!!

Now that I know I have a problem, I think I'm going to go ahead and replace the whole thing again. Here are the numbers that were on my motor:

B523519 Motor
C3575167 Transom
0B560715 Drive Unit

It is an Alpha One drive. I looked at the parts on this site, and I found a kit that looks just like what I have. However, I want to verify with someone here that this is the correct one according to my numbers. Here is the link

Water Pump Kit for Mercruiser 46-96148A8 46-44292A5 46-44292A3, GLM 12120 - Sierra 18-3320 - iboats

Looks like the right kit to me... :D
 

bonzoscott

Senior Chief Petty Officer
Joined
Jul 26, 2008
Messages
745
Re: Totally confused!!!

Now one thing someone told me, was that I should use my rabbit ears to start pumping the water, then submerse it under water before I start it. Is this a true statement?

Now I'm going to replace the impeller here, but I'm wondering about the housing. Can I just scotch brite it clean, or do I need to buy a new one. I watched videos where guys cleaned them up with scotch brite and mild emery cloth.

No on the hose to tub thing. If you visualize where the pump is in the drive, it needs to be submersed in water to start the flow. Water pressure from your garden hose does that.

Condition of your pump housing and scotch brite, depends on inspection. Can't be for sure how many revs you gave it dry or how hot it got. If it looks good, use it.
 

airshot

Rear Admiral
Joined
Jul 22, 2008
Messages
4,222
Re: Totally confused!!!

I for one am not a reuse person, boats cost a lot to run and maintain and yes I do my own work and a lot of work it is. I do not short change anything, if it needs it I put in new and put it in the correct way according to the mercruiser service manual. I try not to wait until something happens, I check my boat after every outing. Knock on wood....I have never had to be towed, and rarely have issues on the water, if I do they have been minor and easy to take care of on the water. I can only attribute this to regular ongoing inspection and maintaince. As I stated earlier...a lot of work yes but in the long run a lot less work.
 

bonzoscott

Senior Chief Petty Officer
Joined
Jul 26, 2008
Messages
745
Re: Totally confused!!!

^^^ Plus One On that! ^^^ but where is there any water in Perrysburg?
 
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