OMC Cobra cooling problem related to leakage at transom?

[daray]

Hello all,

One of my first posts on this forum and I'm glad to have found this forum. I'm from the Netherlands and it's kind of hard to find information regarding the OMC engines and sterndrives.

Since I'm from the Netherlands I might have some issues with using the right words or english grammar, but I'll do my best :joyous:
Now, my question. After rebuilding the complete sterndrive of my OMC cobra V6, we took it to the bootramp for a trial run in the water. I already had an issue with a leakage at the transom so we also took the opportunity to find the spot where the water was coming from.
Well, we found the leak and water is coming in at the back from the top of the transom. After doing a lot of reading on the forum I would assume it's because of a faulty gimball housing seal (?). After reading another posters story that he had the same issue after he hit the ground I remember I also had an encounter with the ground a long time ago. So maybe this caused the leakage.
However, we also discovered that the engine doesn't get enough cooling water pumped through it. There is some water coming out after we detached the hoses, but it's obviously not enough.
The cooling issues can't be because of possible issues with the sterndrive since this has been rebuild completely. I also didn't have any cooling problem to the point that I took the boat out of the water for winter storage. The engine has been winterized.
But I want to be sure, can these two problems have any relation with eachother? What could be causing the problems with the cooling?

I hope you guys can help me with some information. After I bought my Sunbird Barletta 208 it has spent more time at the mechanics than in the water (mostly due to bad and unreliable mechanics). But I really would like to start enjoying my boat, at least for this summer.

Thanks in advance for your replies.

Regards,
Ray

 

[daray]

Re: OMC Cobra cooling problem related to leakage at transom?

In addition to my earlier post: I've done a lot of reading on the forum and it seems that the majority of problems with a leaking transom are at the bottom of the transom.
In my case the leaking only starts when the drive is fully submitted under water, for example when I'm speeding up or when I have some more people with me in the boat, obviously the back gets heavier than and the outdrive will be fully submerged. For example, when the boat is sitting in the water at the dock with no one in it there is no problem with leaking water.

In short, the leakage in my case is at the top of the transom. Could this indicate that there might be another issue?

 

[Levinz11]

Re: OMC Cobra cooling problem related to leakage at transom?

Can you put up some pics of the area that is leaking? Do you think the transom itself is rotting?

 

[Bondo]

Re: OMC Cobra cooling problem related to leakage at transom?

In addition to my earlier post: I've done a lot of reading on the forum and it seems that the majority of problems with a leaking transom are at the bottom of the transom.
In my case the leaking only starts when the drive is fully submitted under water, for example when I'm speeding up or when I have some more people with me in the boat, obviously the back gets heavier than and the outdrive will be fully submerged. For example, when the boat is sitting in the water at the dock with no one in it there is no problem with leaking water.

In short, the leakage in my case is at the top of the transom. Could this indicate that there might be another issue?

Ayuh,.... #1 cause of water intrusion at the transom is rotten wood in the transom,...

#2 cause is rotten/ ripped bellows...

#1 cause of a lack of water flow is a Bad Impeller, which is why changin' the Impeller is the 1st thing to do in any overheat situation...

 

[daray]

Re: OMC Cobra cooling problem related to leakage at transom?

it's kind of difficult to take a picture of the specific area but I can try once I'm at the boat.

Regarding the cooling problem, the impeller has been changed already last week so this couldn't be the cause for the cooling problem.

I've read a lot about the rotten transom being the cause of the leakage, but I'll still keep my fingers crossed it's something else. I'll try tapping around the transom, I believe it's possible to hear if the transom is rotten?

Ripped bellows? Which are the ones to look at?

 

[Bondo]

Re: OMC Cobra cooling problem related to leakage at transom?

it's kind of difficult to take a picture of the specific area but I can try once I'm at the boat.

Regarding the cooling problem, the impeller has been changed already last week so this couldn't be the cause for the cooling problem.

I've read a lot about the rotten transom being the cause of the leakage, but I'll still keep my fingers crossed it's something else. I'll try tapping around the transom, I believe it's possible to hear if the transom is rotten?

Ripped bellows? Which are the ones to look at?

Ayuh,... the Top Big 1, 'n the shift cable bellows,... the exhaust is wet on both sides anyways...

In my experience, knockin' on the transom to find Rot is a fallacy,...

 

[Black as]

Re: OMC Cobra cooling problem related to leakage at transom?

Have a look at your "Y" pipe they also have a tendency to leak at the base, If you can use a mirror.

 

[daray]

Re: OMC Cobra cooling problem related to leakage at transom?

Thanks for all the advice guys. Maybe this will help my mechanic with solving the issues. I'll keep you posted.

 

[Bulbash]

Re: OMC Cobra cooling problem related to leakage at transom?

I've read a lot about the rotten transom being the cause of the leakage, but I'll still keep my fingers crossed it's something else. I'll try tapping around the transom, I believe it's possible to hear if the transom is rotten?

Tapping is absolutely pointless... I just replaced my rotten transom this winter. When I tapped it did sound perfect and uniform in all areas, the only way to check is to drill a small hole, I did it from outside, since it will be easier to fill the hole if test is negative... If shavings will be dark you have a problem if they are light colored than you are good.

 

[Bulbash]

Re: OMC Cobra cooling problem related to leakage at transom?

Here is a pic of my transom that was perfectly sound when tapped from inside and outside...

 

[daray]

Re: OMC Cobra cooling problem related to leakage at transom?

Here is a pic of my transom that was perfectly sound when tapped from inside and outside...

Yikes.....horror...I'll start crossing my fingers all day.. I did decide to have the motor pulled out. Regrettably costs are almost exceeding the value of the boat but than again, selling it like it is will also get me nowhere

 

[daray]

Re: OMC Cobra cooling problem related to leakage at transom?

Good news, the cooling problem has been solved. Only cleaning all hoses and cooler did the trick. Going for a testrun this morning

 

[daray]

Re: OMC Cobra cooling problem related to leakage at transom?

Did a testrun today.

Testrun sunbird omc 2 - YouTube

Testrun sunbird omc - YouTube

After examanation it seemed that the leakage is coming from the steering rod (?). Another mechanic stated that it's probably the transom seal. A lot of guessing going on... I think the only way to have a clear idea of the leakage is to pull the engine out.

The cooling problem also still wasn't quit fixed. Motor temperature increased and than went down again, after that it went up again. This continued a couple of times. The advice was to have an separate pump installed with it's own water pickup, according to the guy the heating problem is a typical OMC problem. What do you guys think? The strange thing is that there was no problem at all with the cooling before I put the boat in winter storage.

 

[Lou C]

Re: OMC Cobra cooling problem related to leakage at transom?

You may be right, the only way sometimes to find the exact source of a transom leak is to remove the drive, remove the engine, re-install the drive and then back the boat into the water. Climb into the engine compartment with a bright flashlight and I bet you will find it.
Cooling system problems are not more common with the OMC Cobra than any other sterndrive, if anything, the impeller is more durable and easier to replace than on a comparable Mercruiser Alpha.
After you get the leak fixed....
Make sure the seal on the impeller housing is really in that groove in the housing. Its easy for it to get out of place when you are installing it and if it does the pump will suck air when you are running on plane, because the impeller is out of the water then.
Make sure there is no blockage in the hose between the transom mount and the thermo housing. What I do when I replace an impeller, is once I have it off I do some tests. I hook up the water muffs and turn on the water. I hold the muffs tight to the drive and water should shoot out of the hole on the right side in this pic. If not there is a problem with the water tube in the lower unit. If thats OK then I disconnect the hose at the thermo housing. I then put a garden hose in that hose and turn on the water. Water should then shoot out of the hole on the left side in the pic. If not there could be old impeller pieces in the hose or in the power steering cooler on the rear of the engine. The manifolds and risers (do they get really hot, as in more than 135 *F?) can clog and that can cause overheating too. Lastly engine issues (blown head gasket) can also cause overheating. It can be tough to track down, but those are the basics....

Here is what my OMC one piece manifolds looked like after 5 years in salt water. In fresh water this is probably a non issue, but not in salt....