OMC overheating,help save my vacation!!!

[fritzies5]

Arrived at our lake rental Sat. night and have been working on the boat since Sun. AM. Here's the scoop: Boat is a Four Winns 3.0 OMC Cobra. It overheated first time in the water. Pulled impeller and it was toast...badly disintegrated. Replaced impeller, housing,o-ring, gasket and plate. Flushed old impeller pieces out of intake hose(pulled off at T-stat housing and back flushed, prior to installing new impeller). Now it will not draw water unless it's hooked to a hose w/muffs. Unhooked intake hose at t-stat housing and water flows only if engine is running and muffs connected. Fed a garden hose into intake hose and back fed water thru the system....water exited at intakes. impeller housing drain, and around prop....no leaks anywhere in intake hoses. It will draw if you start it with the muffs on and then slide them off while running in the water. It pumps fine until you shut it off. Then on restart it won't pump until you put the muffs on again. Any ideas? Please help as my family really wants me to spend my vacation with them and not working on the boat! Sorry for the long post...trying to give a clear picture of the prob.

 

[gadget73]

Re: OMC overheating,help save my vacation!!!

Sounds like the new impeller was maybe installed with the wrong "set" to the blades, and its now partially shot. I'd pull the lower unit again and inspect the water pump installation, something sounds wrong with it.

I'm not really well versed in OMC, but drawing from what I know on other drives, you'd want to make sure that any shaft seals are installed and actually sealing. the wear plate needs to be in good shape, and the housing needs to be free of scratches or grooves. I also like to lube the impellers when installing, just to make sure they don't fail on initial startup. Dish soap works fine for this, and it washes right out with water on first start.

 

[skeat]

Re: OMC overheating,help save my vacation!!!

You have to make sure no air is getting by the raw water pump. If anything looks scratched or worn get rid of it. You can buy the whole assembly OEM (housing included) for about $80 Coat both sides of the gasket and O ring with gasket sealer and be careful installing so that the o-ring doesn't get shifted out of place. It could be other things but this is common.

Good Luck,
Shawn

 

[Stinky_1]

Re: OMC overheating,help save my vacation!!!

I have the exact same problem with my 2.3L OMC engine!!!

I have been messing with it all afternoon trying to sort it out. Lucky enough you can get to the impeller very easy on these drives.

My only idea is that I am getting air into the system somewhere, somehow. I cant see where or how. I even tried some high temp silicone and make my own gasket around the housing. Thinking it must be letting air in some where.

In my case I suspect there is air getting in somewhere between the intakle screens, and the intake side of the impeller. That is why when you start it with muffs on it works. The water pressure from the garden hose pushes water up to the impeller, which can then circulate it. You remove the muffs in water, and its still primed, so its able to keep sucking the water up.

If you do end up getting it sorted out PLEASE come back and post what you did. I am heading to the lake this friday and really wanted to take the boat with me!

One thing I did for my test, was with the impeller OFF, I ran water from the house through the line where it enters the engine BACK towards the impeller. Made sure water flowed that way. Then put it into the impeller hole and watched water come out trough the screens. So I know there is no obstruction in the lines anywhere. I know it HAS to be something to do with the impeller, but what and how to ffix it I have no idea!!

 

[cr2k]

Re: OMC overheating,help save my vacation!!!

Remove the impeller housing and check the position of the liner. The SS liner should be even and level not cocked to one side. Common issue. I have seen some that need to be replaced a few times. New liner in old housing may not fit due to some heat damage from previously running dry.

Good luck.

Oh the impeller turns Counter Clock wise (from the back of the drive) so when you put the housing on twist it clockwise.

Or

Using a large screwdriver twist the impeller in first (clockwise) and align close to the drive tang on the drive. Also important it to clean all gaskets and use aviation permatex on both sides of the gasket. Do not over tighten.

 

[havasuboatman]

Re: OMC overheating,help save my vacation!!!

Remove the impeller housing and check the position of the liner. The SS liner should be even and level not cocked to one side. Common issue. I have seen some that need to be replaced a few times. New liner in old housing may not fit due to some heat damage from previously running dry.

Good luck.

Oh the impeller turns Counter Clock wise (from the back of the drive) so when you put the housing on twist it clockwise.

Or

Using a large screwdriver twist the impeller in first (clockwise) and align close to the drive tang on the drive. Also important it to clean all gaskets and use aviation permatex on both sides of the gasket. Do not over tighten.

Also, that little hose on the back of the impellor housing must be unblocked and spewing water while the motor is running. The reason it is there is to allow the pump to correctly prime. Block it off and you can get a cavitation, or boiling effect, which keeps the pump from working.

 

[sea wolf]

Re: OMC overheating,help save my vacation!!!

Hook up the muffs & look at the impeller housing. If it's leaking you have a bad gasket or the o-ring is not seated. My bet is on the 0-ring or the gasket leaking, allowing the system to suck air.

 

[Stinky_1]

Re: OMC overheating,help save my vacation!!!

we are talking about a outdrive mounted raw water pump. The one in the engine is just for circulating the water that is put there from the impeller.

I know in my case the insert is not twisted at all. Nice and centered.

When I pull that house it is pufing air out of the rubber part. I got the impression that house somehow comes off the exhaust line. it puffs the air in the same rythm as the exhaust. Is that not what it is supposed to do?

 

[Stinky_1]

Re: OMC overheating,help save my vacation!!!

any chance you can recall where someone could look for that screw? i wondered if there might be something like that.

i am thinking for my next test i will pull the impeller out of the housing, put it backonto the drive, then try using my shop vac to pull water through the whole system back there. I may be able to hear or see more with the engiine off.

if it ends up working I am seriously considering putting an electric impeller pump in the boat and running that.

 

[fritzies5]

Re: OMC overheating,help save my vacation!!!

Thanks alot for all the suggestions! We ended up hiring a marine mechanic to come out and take a look. Turns out the problem was that we were doing all our testing either w/the drive partially submerged in a tub or with the boat on the trailer backed into a very steep landing. Mechanic took one look at our setup and said "that won't ever work, get the boat in the water!". Once in the water he had to suck some water into the intake hose and then connect it(with the engine running). All is working well now, we ran it quite a bit last night turning on/off and letting it set between running. Turns out the impeller will not "pull" water up hill. Went out this AM and all is as it should be. We're feeling fortunate to have it going again! Thanks to all, and anyone in the Sevierville,TN area that needs a quick, competant and fair repairman I highly recommend you contact Buster Smith.

 

[Stinky_1]

Re: OMC overheating,help save my vacation!!!

so, i pulled the impeller off again, cleaned everything up and sealed it all very well. This time I have no leaks at all around the housing with the muffs on and water running. Start the engine up, it pulls water just fine. turn off the city water and remove the muffs and the impeller keeps sucking in water from the bucket.

Shut it off and let it sit about 10 minutes and it wont suck any water at all again!

Somehow it is losing it prime. It HAS to be on the sucktion side of the impeller, or else it should have primed all by itself still.

I am wondering if I need to pull the lower leg off and start inspecting the seals leading up to the impeller.

ANyone ever see those go bad and cause this kind of problem? I really hate taking things apart just for the sake of taking them apart!

 

[sea wolf]

Re: OMC overheating,help save my vacation!!!

so, i pulled the impeller off again, cleaned everything up and sealed it all very well. This time I have no leaks at all around the housing with the muffs on and water running. Start the engine up, it pulls water just fine. turn off the city water and remove the muffs and the impeller keeps sucking in water from the bucket.

Shut it off and let it sit about 10 minutes and it wont suck any water at all again!

Somehow it is losing it prime. It HAS to be on the sucktion side of the impeller, or else it should have primed all by itself still.

I am wondering if I need to pull the lower leg off and start inspecting the seals leading up to the impeller.

ANyone ever see those go bad and cause this kind of problem? I really hate taking things apart just for the sake of taking them apart!

First of all you should start your own thread. But, what's with the bucket? If you have it on muffs, how are you using a bucket, & why? This is a new one on me. But, if u have the drive in a bucket with the engine running, yea, it's going to suck water. It's suppossed to. Get rid of the bucket thingy, hook it up to muffs, & see what it does. Can you post a pic of your setup?

 

[Stinky_1]

Re: OMC overheating,help save my vacation!!!

I figured since the posted has/had the exact same problem as me, and had tried the exact same solutions, that it was a natural fit for me to post in here as well. This way, in the future anyone that has a similar problem can see two cases in the same thread.

Anyway, I will try to explain it a bit better.

I have a large bin full of water that the leg is sitting in my driveway. When I start the boat it does NOT suck water up from the leg into the engine.

If I put earmuffs on the leg over the impeller intake screen, turn on the city water, then start the engine, it will suck water. While the engine is still running, I can then turn OFF the city water and slide the muffs out of the way. The impeller will STILL suck water up even though I am no longer force feeding it anything.

If I turn the engine OFF, wait 10 minutes, then start it again it does NOT suck any water up from the bucket anymore.

If I were to put the muffs back on, turn the water on again, start the engine, then remove the muffs, it WOULD still suck water from the bucket again.


My point is, unless I force water in to the impeller at start up, I do NOT get any cooling water from the leg into the engine.

I would suspect this indicates an air leak somewhere. My impeller housing is all sealed up now and does NOT leak water anymore (it did when I first started having problems).

So, I am thinking I may need to pull the lower leg off, and check out the intake system from the screen up to the impeller. But, I dont care much for doing that job.

hopefully its more clear now what is going on.

 

[Stinky_1]

Re: OMC overheating,help save my vacation!!!

I maybe still wasnt very clear.....

the leg is always in the bucket full of water for the test. And the muffs are on the leg while it is still in the bucket. This way when I turn off the city water, and remove the muffs, its still submerged in water. There is no stoppage of flow during the process.

 

[cr2k]

Re: OMC overheating,help save my vacation!!!

DO NOT pull out any screws on the out side of the cobra that are not oil drain screws.

If it was or is covered by a sticker or decal it is NOT TO BE REMOVED.
The 2 screws on the sides of the Cobra are clean outs from casting the drive housing. If removed you will need to pull the drive to replace and then it is a pain in the arse.

 

[cr2k]

Re: OMC overheating,help save my vacation!!!

Is the bucket deep enough to simulate the deep immersion the lower drive would be in in a lake? If not yes there are weep holes to ensure draining of the drives water passages to prevent freeze damage. You are telling me you have a bucket that covers the intake plates that you put the muffs on and water level is at least as high as the cavitation plate??

Also if it is an SX there is NO water pump in the drive, only a belt or crank driven pump on the engine.

 

[Stinky_1]

Re: OMC overheating,help save my vacation!!!

its a large rubbermade bin. It comes up just as high as the cavitation plate. Should it come up even higher than that? I have been worried about going out to the lake to test it if it wont run in my driveway.

If you can let me know where the water level needs to be too then maybe I can stop worrying about nothing.


CR2K you are about 3 hours too late with your warning!!!

in my search to figure out where my leak was, I pulled the screw off the side of the drive. I know EXACTLY what you are talking about.

For the benifit of anyone else reading this. Follow his advice and do NOT ever ever ever pull that screw out.

there is a threaded plate behind it that will fall over sideways, and the screw will NOT thread back in to it. Ask me how I know!!!

And, for those of you who all ready pulled the screw and are wondering what to do....... I pulled the impeller housing, pump and stainless plate off. Then got some 10 gauge wire. I made a hook on one end of it, and pushed it into the cavity where the pump draws fresh water up too. I was able to get it in behind the back of the flat threaded bar, and hold pressure behind it just enough to get a couple threads of the flat screw back into it. Then I tightened it back down.

Take the advise though, I was ready to start pulling the whole drive apart to put that stupid screw back on. So, if you can refrain, please do!!

I am not sure what drive the OP has. But mine is a cobra and deff has a impeller pump in the out drive. Its driven off the shaft that comes through the transom into the drive. I have looked at it many many times over the last couple days taking it off and putting it back on again.

I will have a look to see if those holes are covered. I really hope that they are NOT being covered by my bucket of water, and that is what my problem is! My manual didnt mention anything about them. Either that I didnt pay any attention to it.

thanks for the tips so far everyone

 

[Stinky_1]

Re: OMC overheating,help save my vacation!!!

please please please tell me that you are talking about the 2 slots y ou can see just above my cavitation fins!?

does that part need to be under water for me to ever hope for it to suck water up on its own? if so, I will be out at the lake tomorrow to test it out!

 

[Thajeffski]

Re: OMC overheating,help save my vacation!!!

Read his last post. He says that the impeller doesn't have enough power to suck water up much.
Take your boat, put it in the water and see what happens........

The guy just said that the mechanic said buckets don't work.

 

[Stinky_1]

Re: OMC overheating,help save my vacation!!!

yeah, I saw that.

I was always under the impression that running a boat in a bucket, barrel or otherwise was always prefered over using the muffs. I am starting to think I was missinformed.

I will be taking it to the lake tomorrow to try it out. hopefully once those holes are under the water too all my problems will go away. I feel like a fool, but probably have learned something.

here is to hoping it works. Ill post back when I have my results.