OMC Cobra 3.0 Overheating

Author Message   Greg Reichert Visitor Posted on Saturday, April 19, 2008 - 11:37 pm:    I was starting my boat for the first time of the season yesterday, and after hooking up the muffs and turning on the ignition all went well initially. The engine ran smoothly, after getting up to temperature, about 160, the pump seemed to cycle fine as I watched all of the colored antifreeze slowly pump out of the sterndrive. It maintained its temperature well, so I shut it down and proceeded to change the oil. After changing the oil, I started it back up to get oil into the filter and check the level, but the boat proceeded to heat past 160 and it never cooled down. I quickly turned it off and waited to try again with the same result. I then looked on a forum and read that if I unhooked the thin top hose that goes into the thermostat housing coming from the impeller and no water came out while engine was running, the impeller was at fault. I tried this and no water came out of the hose with engine on. I'm just trying to figure out if it might be my impeller or if the thermostat might be bad. I don't understand why it would have worked upon initial startup but not 30 minutes later after changing the engine oil. It also overheated momentarily when I was winterizing it with one of those winterizing kits that you hook up to the muffs, but it didn't seem to be able to suck in the antifreeze. I shut it down at that point and hooked up the muffs directly to a garden hose and it cooled back down. Now, however, it continues to heat past the 160 degree mark at all times. Any help would be appreciated. If it is the impeller or thermostat, can I fix these myself. I am handy, but a newbie boat owner. Thanks, hope post isn't too long...   Morten Ringvold Senior Member Username: haffiman37 Post Number: 2641 Registered: 04-2006 Posted on Sunday, April 20, 2008 - 12:14 am:    Take out the impeller and check. Behind the rear cover on the drive(2 screws at top, 1 down), then 3 screws for the pump housing. Note that this system is not self sucking, and You might have burned it during winterizing.   Greg Reichert Visitor Posted on Sunday, April 20, 2008 - 08:32 am:    Morten, thanks so much for the response...I am sorry to ask but I can't find the '(2 screws at top, 1 down)'. Do I have to drop the drive by removing the four hex heads at the very top of the drive by the oil level dipstick in order to get to the screws that you are talking about? Will the pump housing then be evident. Thanks for your patience and expertise.   Hy Stat Advanced Member Username: hystat Post Number: 235 Registered: 05-2007 Posted on Sunday, April 20, 2008 - 09:40 am:    Cobra impeller is serviced without removing the drive - invest in a manual. There's several pages on the subject - even if we could type real fast we're gonna forget some detail some time...   Morten Ringvold Senior Member Username: haffiman37 Post Number: 2644 Registered: 04-2006 Posted on Sunday, April 20, 2008 - 10:09 am:    Screws #62.   Greg Reichert Visitor Posted on Sunday, April 20, 2008 - 11:33 am:    Thanks Morten, after your last post I did hunt and find this diagram on another site and I found the screws to which you are referring. My engine is, I believe, an '85 and I think this diagram was labeled beginnng in '86. My boat just has four screws at the top that hold the - I want to say - lower unit on the drive. If I invest in a manual, is my impeller as easily serviceable/found or should I just take it into the shop? They're telling me it's a $350 job, so I'm wondering if it's inaccessible. Thanks again so much...   Bob Hill Advanced Member Username: boatin_bob Post Number: 525 Registered: 07-2006 Posted on Sunday, April 20, 2008 - 06:46 pm:    Greg...is your drive a Cobra or a Stringer? 1985 was the last year for Stringers and 1986 was the first year for Cobra's (Picture above is a Cobra). Does your drive have a big rubber seal around it or does it have 2 hydraulic cylinders (one on each side) to trim/tilt with?   Greg Reichert Visitor Posted on Sunday, April 20, 2008 - 07:23 pm:    Bob, the more I've been reading, the more I think mine is a stringer. It would be nice if I knew what I had..eh. It does have the big rubber seal - bellows I'm assuming - and there are no hydraulic cylinders. It has the selecttrim where the entire engine moves up and down to trim the sterndrive. I was led to believe it was a cobra by the marina where I purchased it, but I don't think they no much more than I. Also confusing is that some manuals I see online say OMC cobras 1986 - ... and one says OMC sterndrives 1985-... I'm hoping to be able to do this job myself, but I'll need to know where to hunt to find impeller. I'll need to know which manual is appropriate to purchase for this boat...or maybe you're going to tell me that this is no DIY job. Thanks for the further enlightenment. You guys are invaluable.   Morten Ringvold Senior Member Username: haffiman37 Post Number: 2647 Registered: 04-2006 Posted on Sunday, April 20, 2008 - 08:17 pm:    If a Stringer the upper unit look like this, and drive has to be removed to get off the upper unit and gain access to the impeller.   Greg Reichert Visitor Posted on Sunday, April 20, 2008 - 08:31 pm:    That's the one! Thanks...so is this the manual to buy - OMC STRINGER STERN DRIVES 1964-1986? It's a SELOC manual.   Morten Ringvold Senior Member Username: haffiman37 Post Number: 2652 Registered: 04-2006 Posted on Sunday, April 20, 2008 - 09:03 pm:    That is the 400 Stringer drive. You get it from this site. Read first, then do the job. Good luck.

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