OMC 4.3 - Water Not Circulating thru Engine

[janas4play2]

Newbie here, please be nice.
= )
I found there is no water circulating thru the engine. How do I go about diagnosing if the problem is with the water pump or the impeller or??
Also, if there is a crack in the exhaust manifold, would that cause the lack of water circulation in the motor?

I am NEW to all of this, don't really have the funds to give to a shop at this time...just looking for a start.

Thanks for any input.

 

[jtmarten]

Re: OMC 4.3 - Water Not Circulating thru Engine

You can pull the hose that feeds the engine from the drive/impeller. Fire it up for a few seconds and see if she's pumping water. If not replace the impeller. You can check water pump operation by using a garden hose where you disconnected the water feed hose. Fire it up and see if she's pumping through.

If the impeller is more than 2yrs old, or if you don't know the age, just replace it. Cheap insurance, and you'll know it is good.

If the manifold is cracked externally, you'd know if the impeller was OK since it'd be spewing water out of the crack. If it's cracked so water can enter the cylinders, I wouldn't run it until you replace the mani.

 

[janas4play2]

Re: OMC 4.3 - Water Not Circulating thru Engine

Thank you for your reply.

I know there is a crack externally, the impeller appears to be okay, I'm not sure of the age. Another question I have, is how do you know that the impeller is spinning?
I don't know if this information is important, but it's an I/O motor.

I apologize for my lack of knowledge, I am new to boats. I think I may have gotten in over my head.

 

[bruceb58]

Re: OMC 4.3 - Water Not Circulating thru Engine

If you have a cracked manifold, why aren't you replacing that first?

Also, if you don't know how old the impeller is, just replace it. Its easy on an OMC Cobra.

 

[janas4play2]

Re: OMC 4.3 - Water Not Circulating thru Engine

Thanks Bruce, I will replace both, just the not knowing where to start first is driving me crazy.
= )

 

[CountryCruiser]

Re: OMC 4.3 - Water Not Circulating thru Engine

Yes, try everything in the above posts. I had this same issue last year when I went to summerize. I still can really tell exactly what it was but here are a few more ideas to try:
1. Remove the outer half moon cover off of the top of the outdrive. You will expose the impeller housing. There should be a vent hole in the impeller housing, in think on the lower left corner, make sure this is not plugged up. When you hook the hose up to the intake, water should come out of this vent hole. When you start the engine water should REALLY shoot from this vent hole. If if does, you at least know that you are getting water to the impeller.
2. When you replace the impeller, and I hope you will, remove the impeller and housing and take the raw water supply line off at the thermostat housing. You should be able blow air or water back from the thermostat hose through the power steering cooler to the impeller. If this flows well you don't have any restrictions there either.
3.Get a short, 6" or so clear piece of hose the same I.D. as the raw water supply hose. Using a coupler and hose clamps, attach one end to the end of the raw water supply hose and the other back to the t-stat housing. This will give you a quick and easy visual to see if water is making to the engine even after you have fixed your problem. Make sure you see no air bubbles when the engine is running, or you may have a leak somewhere down the line.

Hope this helps and it might be a good idea to change the thermostat while you are at it. Oh, and get ready to bend over for the exhaust manifolds unless you can have them welded!

 

[bruceb58]

Re: OMC 4.3 - Water Not Circulating thru Engine

Thanks Bruce, I will replace both, just the not knowing where to start first is driving me crazy.
= )

Why is your manifold cracked? If it was from freezing, are you sure your block isn't cracked too? What is the history of you with this engine? Has it ever run properly while you owned it? Any other issues?

 

[janas4play2]

Re: OMC 4.3 - Water Not Circulating thru Engine

Thanks for your question.

Unfortunately, I just purchased this boat for a low price from "a sweet ol' lady" who stated that her and her husband went to get it ready for the summer and discovered a milky water/oil mixture. Figuring it was a blown head gasket they didn't want to bother paying to fix it or try to work on it themselves.
I purchased against my husbands better judgement thinking this would be a great "family fun" purchase.....not too bad, you know a quick fix??
Ha!
I'm sick thinking of what I just got in.....(or bent over...LOL)

But, regardless of my bad judgement, I/we don't know very much about the boat, it's in great body/interior shape...the engine looks okay, what I thought was a cracked manifold appears to be QuickSteel so I am assuming there was a crack somewhere.
We placed new oil and an oil filter and started the engine up, that's when we realized it didn't appear to have water running thru the engine.
After inspecting the impeller, it looks in fair shape, no shredding or anything that looks out of order, but I will replace nonetheless.
And, if it matters or ?? there doesn't appear to have water in the oil now, but I guess that could be due to the fact that there is no water running thru the motor?

I'm trying to read the boards to gain information, and reading the Seloc book is somewhat informative, but confusing to a newbie such as myself.
I am hoping that with everyones input, I can get some direction as to where to start first.

Thank you again for your time, it's greatly appreciated.

 

[daymienrules]

Re: OMC 4.3 - Water Not Circulating thru Engine

just to confirm, you do have have the garden hose attached to the muffs and supplying water to the engine right? I could see how a new boat owner might not know to do that if they were never told to.

 

[bruceb58]

Re: OMC 4.3 - Water Not Circulating thru Engine

OK...now that we know a little more info, you might want to do some different things before even repairing the water pump. I would first pressurize the cooling passages of the block to check for cracks. The fact that the manifold was cracked points toward that and not a blown head gasket. Once you know that info, you then have to make the tough choice to spend the money on a new engine or just cut your losses.

 

[janas4play2]

Re: OMC 4.3 - Water Not Circulating thru Engine

Thanks everyone, got the water circulating, found out the block is cracked.

Another one bites the dust.
I'm optimistic though, I'll stuff a new engine in it and have some fun.
(all I can do)

Take care & happy safe boating to you and yours.

 

[janas4play2]

Re: OMC 4.3 - Water Not Circulating thru Engine

Ooops, forgot to ask...is there a engine I can swap my 4.3 for or should I just stick with that?
Thanks!

 

[fossill]

Re: OMC 4.3 - Water Not Circulating thru Engine

The 4.3L is a great engine, good on power and good on gas. Be it me, I'd get a brand new GM crate engine from your local GM dealer and marinize it. That way you get a new engine at an economical price. I'm not a big fan of rebuilt engines as most budget ones just have useable old parts put back in.