My pet gremlin moved on my 1989 OMC 3.0. Need help with cooling sytem.

1989, 20 ft baja, omc (GM) 3.0l, cobra drive.
Ok, so now I have a new problem that I cant seem to get figured out.
I finally got my engine to run great, however, I had to shut it down after few minutes due to it getting to overheat temp.
At the dock I dropped the lower unit and was mentally patting myself on the back because the engine was running so well when I noticed it was getting hot.
I pulled the inlet hose from the thermostat housing and found I wasnt getting any fresh water to the engine. I pulled the boat out and looked at the impeller. all looked well, the impeller is new and was installed twisting it in counter clockwise. I put one in when I first started working on the boat.
With the hose off I noticed that the hot water from the engine side was shooting out but nothing was coming from the impeller or supply side.
Got back home and pulled the housing off, as well as the impeller plate and the gasket behind that. I did notice some small drips of water from this area when on the muffs so for a quick fix to see if it would work, I added a very thin layer of sealer to the gasket surface.
No leaks on the muffs so back out to the lake. Left it on the trailer, lowered the drive, fired it up, same darn thing. I get no fresh water when at idle, I get some water at around 1300 rpm or so, but it almost seems that the impleller dosent have enough umph to overcome the pressure of the hot side. The supply line was also hot so that makes me think this as well.
I made an observation on the liner of the impeller housing. At the top of the kidney shap there was a gap of about 1/32" which would make the liner less than perfect shape.

Q: Is this enough to cause my problem?

By the way, at home I ran hose water from the bottom with the impeller cover off and the water flowing good. I also ran the garden hose from the hose at the thermostat housing and good flow to the impeller . No obstructions.
I'm stumped! .
Thanks
Offshore 79

Re: My pet gremlin moved on my 1989 OMC 3.0. Need help with cooling sytem.

"was installed twisting it in counter clockwise"
Duh! I just looked at the book again and I was in the King Cobra section. King cobra is counter clockwise, cobra is clockwise.
Can someone just slap me.
Back to the lake!

Re: My pet gremlin moved on my 1989 OMC 3.0. Need help with cooling sytem.

That didnt do it.
When I take the hose off the thermostat housing I get water to flow, when I put it back on, the hot side overcomes the cold side.
Does anyone know why this would be?
Could there be a leak somewhere between the gimbal housing and the upper case?
I just removed the impeller housing again to see if the vanes we good and I noticed the liner is off center.
Should this be off center or did it shift at some point.

Re: My pet gremlin moved on my 1989 OMC 3.0. Need help with cooling sytem.

Cracked the head on a mercruiser 140 after changing the impeller and the engine still overheated. The bits of the old impeller were hiding in the bottom of the outdrive water intake where I didn't think to look.(bonehead) Those four small bits of rubber would intermitently clog the intake causing an occasional overheat condition until finally they jigsawed themselves together to totally clog the outlet pipe from the pump and being in the wilds of Georgian Bay with the kids at the time I badly overheated her and wrecked the head to get back to shore

Re: My pet gremlin moved on my 1989 OMC 3.0. Need help with cooling sytem.

offshore79 said:

"was installed twisting it in counter clockwise"
Duh! I just looked at the book again and I was in the King Cobra section. King cobra is counter clockwise, cobra is clockwise.
Can someone just slap me.
Back to the lake!

Click to expand...

It looks to me like u need a new liner & possibly the housing. I would order a new water pump kit which will include the above & a new plate. If it's leaking from the bottm of the housing, the plate may be warped, which will cause the pump to suck air. And gasket sealer won't cure it.

Re: My pet gremlin moved on my 1989 OMC 3.0. Need help with cooling sytem.

Sea wolf,
I plan on getting the impeller kit and housing but I'm not so sure it's the problem.
When I pull the hose off the thermostat housing I can hear the water coming and then it pumps it out great. (I could fill a gallon of water in just a few seconds.) I do however get hot water jetting out of the thermostat housing which, with the hose back in place, seems to overpower the flow from the impeller.
I wonder it there is a restriction after the thermostat causing this. Like maybe a clogged exhaust elbow.
I inspected the exhaust manifold and it's clear but when I got to the elbow I chipped off allot of rust. Now that I think of it, I didn't fully inspect the elbow when I had it out.
I plan on doing this when I can get back to it.
Just a thought here, if the engine is up to temp, and if the thermostat is open, the water should be passing right thru to the exhaust manifold right? Should I see much water jetting out the cold water inlet on the t-stat housing?

I bought the boat at an auction thinking the engine needed to be replaced but the engine components turned out to be, for the most part, salvageable. I think I'm now getting into the things that caused it to fail and ultimately be auctioned.

Re: My pet gremlin moved on my 1989 OMC 3.0. Need help with cooling sytem.

Is water coming out thu the exhaust?

Re: My pet gremlin moved on my 1989 OMC 3.0. Need help with cooling sytem.

Sea wolf,
Yes it is on the muffs. It looks like it comes out well but I thought maybe not enough...........

Re: My pet gremlin moved on my 1989 OMC 3.0. Need help with cooling sytem.

Well, new impeller (again), only this time also a new housing, liner, gasket, metal plate. Still only get water when I take the fresh water hose off the thermostat housing.
Again, when on the muffs, water passes thru the lower unit and passes thru when I feed water from the end of the fresh water supply hose.
What to do?

Re: My pet gremlin moved on my 1989 OMC 3.0. Need help with cooling sytem.

Here's one I havent read yet.
I attached a garden hose to the fresh water hose up by the thermostat but this time left the impeller and housing in place.
I found a significant amount of water coming from the gimbal housing area. I looked in and a stream of water was shooting out of the side of the hose and seemed water was coming from where the hose connects to the out drive as well.........Did I find my gremlin finally?

Off comes the lower unit.....again!

Update. Didnt do a darn thing.
I took the lower unit off, repaced the hose from the transom to the hose fitting in the drive.
I also used a thin coat of sealer to make sure therre was a good seal between the gimbal housing and the gear case.
Just on an off chance, I put the garden hose in the hose to the exhaust and that seems to be clear too.

Theres nothing left. I'm pretty sure Ive been through everything now.

Re: My pet gremlin moved on my 1989 OMC 3.0. Need help with cooling sytem.

Ok, I think I have one more thing left to try. When I was running the boat at the dock and added some throttle, I could feel air bubbles in the supply hose to the thermostat. From what I read, this could be an indicator that something could be out in the water pick up tube assembly and exhaust is getting in the supply. I guess I'll be removing the lower unit again and parting the case.
Any words of wisdom before I tare into that?

Re: My pet gremlin moved on my 1989 OMC 3.0. Need help with cooling sytem.

To any of you that are paying attention to the ramblings of a DIYer, I've got another update.
I pulled the outdrive (#3, I think) and this time I pulled the lower from the upper to see if there was anything missing or lodged in the lower unit. This is what I found.
I think there may just be a problem with this.


And I'm not sure where the washer came from but it's melted in there


Needless to say I'm off shopping for some parts again. Two pick up tube seals and one tube guide.
It looks like whomever worked on the lower unit in the past probably installed the tube in the lower unit first, thru the tube guide and into the tube seal, and tried to slide it into the upper. The guide is called guide for a reason. The tube should be installed in the upper first and then fed into the guide when putting the lower back on..
NICE!

Oh, and for all of you that wondered where that little hose from your impeller housing went, here you go.


Wish me luck on this, I've got nothin else I can do.
offshore79

Re: My pet gremlin moved on my 1989 OMC 3.0. Need help with cooling sytem.

I took it to the water last night.
I put the boat in, pulled the hose off the thermostat housing and set it to the side. I turned the key, started good........waiting...thar she blows!
I let it run at idle for awile finally after 5 minutes realized it normally would have been at 200+ degrees by this time.
After about 10 minutes worth of idling It was around 175.
I ventured out into the lake and ran it (close to shore) for awile at about 2000 rpm, then about 3000 for about another 3 minutes, then at around 4000 for about 10 minutes.
I finaly started to work to WOT. 4200 for a few minutes, then 4500, 4800, and a burst at 5000+ RPM......Need to reprop. 15 to 17 I think.
175 ish the entire time. WoooHoooo!

The gremlin is gone!

Re: My pet gremlin moved on my 1989 OMC 3.0. Need help with cooling sytem.

congrats and good to see the outcome! It looks like at some point in the past there was a bad overheat and that melted the seals for the water tube. That circular retainer looks like the ones used to hold the plastic thrust plates on the forward sides of the upper unit.
I also had a mild running hot issue this year, what it turned out to be was exhaust manifolds starting to clog, and barnacles growing in the water intakes. In oder to test this theory, without splitting the drive, I broke out the water screens at the 4 intake holes on each side of the lower and used a stiff piece of wire to clean out all the barnacles inside. The engine used to run at 175 abut would heat up to about 185 after coming off plane. After cleaning out the water intakes, it ran at 165 and only heated to 175 after coming off plane. Now I know I have to replace that water intake screen but at least I know that was part of the cause. I know the Merc and Volvo drives to not have a screen for the water intake but they use 6 smaller holes on each side vs the 4 large holes on the Cobra. The Cobra's lower design is OK on an outboard (which it was adapted from) but for an I/O moored in the water (salt) you will get barnacles growing in there. I'd like to see an external screen design that can be removed for cleaning like on the late model Evinrudes.....