'91 OMC Cobra -- Transom Leak

Status
Not open for further replies.

johnbo

Petty Officer 2nd Class
Joined
Mar 19, 2006
Messages
165
I've been helping my buddy chase a leak in his 20 ft. Reneill. It has a 5.0L carbed Ford with the OMC Cobra in it. At the end of last year, he had a leak from the bottom of the transom cutout into the bilge that was a pretty good stream. About the diameter of a wood pencil. I had warned him that this sounded like a rotted transom.

My buddy has owned the boat since it was new and said that it always had water in the bilge at the end of the day, but the leak seemed to getting worse year after year. When the boat was about a year old, he loaned it to a another person who tagged a stump with the outdrive. The outdrive was replaced by an OMC dealer via insurance.

Other than this, the boat is garaged in a heated garage, and gets about 20-25 hours of use at the most per year (190 hours total).

On advice from this site, I built up a somewhat overbuilt gantry and pulled the engine this weekend. I inspected the wood at the cutout (what I could get at), and it is clean and dry, even at the bottom of the cutout. I noted that the bottom 4 bolts (out of the 6) were loose. For example, the little U shaped piece between the bottom two bolts would rattle. The top two bolts were tight. One of the middle bolts would even shift sideways just a little bit.

We took the boat down to the local ramp and backed it in, attached to the trailer. Found that the water was apparently coming from above the bottom two bolts. mostly on the steering rack side of the boat. Having confirmed that the leak was the same as last year, I tightened the bolts down to about 40 ft lbs (using my calibrated arm). The leak greatly diminished, but is still there, just enough to form a wandering stream. Sounds like time for a gasket....

I spent a lot of time banging on the transom with a rounded end of a wrench, and everything sounds really solid. The lags on the front engine mounts came out clean and dry. So, it doesn't feel like a rotted transom. No cracks or checks in the gelcoat on either side of the transom. When I aligned it last year for the first time is 8-10 years it was spot on.

But, how could the transom bolts get loose?

With the engine out, how much more work is it to change the transom seal?

Would this be a reasonable fix? With any chance of success?

Your thoughts are appreciated. (Sorry about the long post).

johnbo
 

mjhamilton4

Cadet
Joined
Jul 26, 2011
Messages
11
Re: '91 OMC Cobra -- Transom Leak

i know this is an old thread but we are having the EXACT same problems as you with our 1991 omc cobra. just curious if you ever found the cause of this...we are going to pull the motor today. bolts did seem loose but as you stated....why would that happen?? just wondered if you replaced the seal and if that helped or if you did find another cause and eventually got yours fixed....it doesnt appear to be our transom either but yet leaking under it? kinda weird that you hit the nail on the head with everything you said being our problems as well! thanks for any help!! we are really scratching our brains!
 

Don S

Honorary Moderator Emeritus
Joined
Aug 31, 2004
Messages
62,321
Re: '91 OMC Cobra -- Transom Leak

i know this is an old thread but we are having the EXACT same problems as you with our 1991 omc cobra.

You may have the same problem, but you should get in the habit of starting a new thread when you have questions and not use someone elses thread for your questions.
 
Status
Not open for further replies.
Top