Over Heating Problem

[merit131]

1989 OMC, Corba 5.0L Ford V-8. Last year fine. I changed the thromostat. The old one was really shot. When I took out the old one, there were no copper arms on the stat, just spring and the upper part. I think the old arms may have went into the water pump below the stat and maybe damaged the pump, not sure. When I start the engine the gauge slowly creaps up all the way. Then I let it cool, and did it again with the boat in forward gear, thinking the boat needs to be in gear to get the outdrive pump working to pull in the raw water from the ocean. But the same thing, goes all the way to hot.

I removed the new stat and took it home to check in pot of hot water, and it opens fine reinstalled the stat but still have problem. It's the right marine stat.

Any ideas on how to give a test to see whats going on with pumps, outdrive pump and motor pump while still in the water? Thanks.

 

[Kainon]

Re: Over Heating Problem

Well.. the water pump on the front of the engine if the vanes inside are worn, will result in not enough water flow through the heads and block which can cause and over heat however unlikely.

Have you EVER run the engine without providing water some how? If you did, you've destroyed the Impeller in your Raw Water Pump

The engine/drive doesnt need to be in gear, if you have an inboard, your pump is on the front of your engine.
If you have an outdrive it most likely is in your outdrive.

Do you have an Sterndrive? or Inboard? (prop under the boat)

you probably have an SX Drive which is pretty easy to change, should be instructions or pics here somewhere..

you may have peices of the impeller in the cooling system somewhere too

SO.. also when you have a boat in the water for extended periods, can also get marine growth in the pickup holes, this will
restict the flow..

you'll have to get the boat on the trailer, or pulled to get to the pump impeller.

 

[merit131]

Re: Over Heating Problem

Hi Chief: Yes an IB/OB, yes I have the two pumps like you said. I just put the boat in the water last week. Today I removed the hose from the thromostat, the hose that is the supply to the engine from the outdrive. I then attached a clear hose (12in long) and reattached it back to the stat and started the engine to see if water was going to the engine, and it was not. So I beleive your right the pump in the out drive would need to be changed. Yes, I got the manual from this site and it looks like a pretty easy job to change. I'll do that first and see how it goes. If still over heats, I'll do the front pump as well on the engine. As you can see by the pic, I built a new engine hood and seat, so I would need to remove all that to get at the engine pump. I may have about 4 in clearance back there. Thanks let you know how it goes. Murp

 

[HT32BSX115]

Re: Over Heating Problem

1989 OMC, Corba 5.0L Ford V-8. Last year fine.
Any ideas on how to give a test to see whats going on with pumps, outdrive pump and motor pump while still in the water? Thanks.

Howdy,


Your OMC Cobra has a rubber impeller type pump on the back of the outdrive that has most likely failed.


You need to change it and if it has a LOT of pieces missing on the old one, you'll need to locate them to ensure that they're not plugging up the power steering cooler etc.

It's very unlikely that your circulating pump (on the front of the engine) has failed.

If you're not sure how to change a raw water pump on a Cobra, do a search. Get yourself an OEM OMC (NOT SELOC/CLYMER) service manual for your year model drive. there's also several Youtube videos on how to do it.


Um, by the way, if it's an 89, It's NOT an SX (Volvo) ...... They didn't exist until around the mid 90's

Regards,


Rick

 

[merit131]

Re: Over Heating Problem

Chief, I have one question. Do I need to put the boat in gear to get the sterndrive pump pumping, or will it work (pump) while in nautral?

 

[HT32BSX115]

Re: Over Heating Problem

Chief, I have one question. Do I need to put the boat in gear to get the sterndrive pump pumping, or will it work (pump) while in nautral?

The raw water pump operates anytime the engine is running. If there's no water to it either from being in the water or from a flush adapter, it's destroyed in less than 1 minute.

 

[merit131]

Re: Over Heating Problem

Thanks Rick, The only concern I have w/ the circulating pump is, when I took out the old thromostat thos copper arms that are attached to the spring were gone. So I said to myself, oh oh, they mayhave droped into the circulating pump and maybe messed up those vains, not sure ofcourse what condition they were in when they detached from age. I guess the only way to find out is to remove that pump, or just see how the boat goes when I change the outdrive pump. Thanks Rick, I let you know.

Rick, Do I need to put the boat in gear to get the sterndrive pump pumping, or will it work (pump) while in nautral?

 

[merit131]

Re: Over Heating Problem

Thanks for your speedy reply Rick. Very helpful.

 

[HT32BSX115]

Re: Over Heating Problem

You can certainly remove your circulating pump and inspect it. Many of them have a metal plate on the back that might prevent you from seeing the impeller. The impellers are usually cast iron. It's unlikely that that the brass parts from the t-stat hurt it....

The raw water pump (and the "upper" gears in the drive for that matter) turns anytime the engine is turning.

Looks like we're literally posting at the same time!!

You should probably buy a raw water pump kit for your cobra. If it hasn't been replaced in a few years.

Have a look at the following thread.

http://forums.iboats.com/showthread.php?t=334348

The manual there is a 1990 model but the instructions for changing the raw water pump is the same as is a LOT of other stuff.

 

[merit131]

Re: Over Heating Problem

Yes we are posting at the same time, my quite time. Thanks Rick a few before and after pics hope you don'r mind, I'm just showing off.

 

[merit131]

Re: Over Heating Problem

A few more pics,

 

[HT32BSX115]

Re: Over Heating Problem

A few more pics, View attachment 148608View attachment 148609View attachment 148610View attachment 148611View attachment 148612

Nice job on the interior!

 

[merit131]

Re: Over Heating Problem

I am pretty sure it is the pump in the outdrive. What I did was, remove that hose from the (from the outdrive pump, boat in water) at the tromostat and added a clear hose of about 12in and started the engine, no water passed to the stat. So that is the problem for sure. I will change that and see if the over heating problem is gone. Thank you. Will post outcome.

 

[merit131]

Re: Over Heating Problem

Well it's not the impeller. I installed a new one and still have the same problem. No water getting to the engine. The old impeller was a little chewed up. I took the small hose off the impeller housing and blew in it and heard air coming out somewhere inside the lower unit. I then attached the rabbit ears and turned on the water, but no water came out of that small hose.

OMC Cobra 1989 outdrive.

Question 1: That small hose going to the impeller housing, is that the only water supply to the engine? It comes out of the lower unit, about 1/4 in to 3/8 in dia.

Question 2: Is there another water supply that comes out of the lower unit to that impeller or to the engine eleswhere?

 

[HT32BSX115]

Re: Over Heating Problem

The small hose is a "vent" tube. If you remove the impeller housing and put "muffs" on the drive, you should see water at one of the ports when you turn it on.

No water getting to the engine. The old impeller was a little chewed up.

How many "old impellers" have been chewed up over the years? You may have impeller fragments (and other debris) in the hose that goes from the transom mount to the t-stat housing, completely clogging it.

 

[merit131]

Re: Over Heating Problem

Thanks Admiral, Got your message and will post here so everyone can see.I checked all hoses and cooler hoses for clogging, but seem ok.

As you asked, I put on the muffs with the impeller removed and no water was coming out of the ports. I assume I have a clog in the lower unit. From what I see in the diagrams, it looks like a screen cartage in installed below the water housing in the lower unit. I don't like removing the lower unit, but I guess I'll need to and replace that screen or check for clogging. Do you agree?

 

[merit131]

Re: Over Heating Problem

If you remove the impeller housing and put "muffs" on the drive, you should see water at one of the ports when you turn it on.

Well you were right, and as I said I did that, but today I did it again and this time I took both hands and applied pressure to the muffs and sure enough, water poured out of the impeller port, this primed the impeller pump. Thanks all for your help. Cooling problem solved.

 

[merit131]

Re: Over Heating Problem

I spoke too soon. Over heating porblem not solved! Today I went to WalMart and purchased a big plastic storage box that I could fit under the Outdrive. I then filled it up w/ water over the intake holes. I wanted to make sure the impeller pump would work and pump the water to the thormostat, as if it was in the water. I started the engine and IT DID NOT WORK, no water came up to the stat. I still had a 12in peice of clear hose attached to the reg hose to see if water passed to the stat. No good. I don't know whats doing on, all hoses are clear of blockage I think I may have damaged the new impeller when testing for flow. It looks good, but I don't know. all hoses are tight, so I don't think air is getting in.

Yesterday when I had the rabbit ears on and applied pressure w/ my hands on each side, it was the house pressure that was making the flow and not the impeller pump. Tomorrow I will pull the impeller off again and make sure the gear shaft in turning, (the one that turns the impeller. This thing is got me nuts already. Any thoughts out there ????? Jack

 

[HT32BSX115]

Re: Over Heating Problem

I took both hands and applied pressure to the muffs and sure enough, water poured out of the impeller port, this primed the impeller pump.

That should have proved that you don't have some sort of blockage between the intake ports and the pump inlet....

Today I went to WalMart and purchased a big plastic storage box that I could fit under the Outdrive. I then filled it up w/ water over the intake holes. I wanted to make sure the impeller pump would work and pump the water to the thormostat, as if it was in the water.

But it's really NOT like being in the water....


You really cannot just put the out drive in a bucket of water like an outboard and expect the pump to prime.

It works with an outboard because the level of the water in a bucket is usually at or above the level of the pump (which puts water into the pump before it starts turning) Same with an Mercruiser Alpha The actual position of the pump makes it submerged when you put the drive about halfway into the water.

With a Cobra, the pump is higher up on the drive making it a little harder to prime.

You need to use a flush adapter or put the boat in the water.

Tomorrow I will pull the impeller off again and make sure the gear shaft in turning, (the one that turns the impeller. This thing is got me nuts already. Any thoughts out there ????? Jack

Those pump shafts have been known to break. It that's happened, the impeller won't be turning (and you've found your problem!)




Regards,


Rick

 

[merit131]

Re: Over Heating Problem

Thanks Rick for that info. I'll be back Jack