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9394 30 OMC Cobra Drive

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samm835

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"Great site here guys! I have

"Great site here guys! I have recently bought a 94 or 93 Sunbird with a 3.0 OMC motor. I took the boat out on the lake a month or so ago and the it ran hot, so I took it in and had the impeller replaced. I took it out again last weekend and it still seems to be running hot according to the t-stat. Can someone else here help narrow my issue's down? We know the impeller is new, so is there another one on this motor I don't know about? I am also going to change the Fuel seperator and fuel filter tonight when I get to the lake, are these fairly easy to change...I do have a manual, just not here at work so I don't remember where they are.
Thanks in advance!"
 
"How hot? Take the raw water

"How hot? Take the raw water hose lose at the engine. Start it on muffs long enough to see if water is actually being pumped. If so, check / replace your thermostat."
 
"Just out of curiosity...what

"Just out of curiosity...what if there isn't water being pumped. What would be my next problem, I noticed last night while working on it water is leaking from somewhere I just haven't found from where yet......any suggestions on where it more than likely is coming from? The more I write about this the more I am thinking something is cracked."
 
"Need more info here as there

"Need more info here as there are huge differences between a 93 and 94 drive. Give us the model # off the drive or the engine to determine the year (not the year of the boat). 93 had a raw water pump in the drive, 94 went to the cone clutch and an engine mounted belt driven raw water pump.

Also be more specific about the leak, inside the boat or outside?"
 
The above test would tell you

The above test would tell you if your raw water pump (the one in the outdrive with the new impellor) is supplying water to the engine. If not there is either a problem with said pump or a restriction in the line. You can then stick your water hose into the supply hose (the one you took loose at the engine) and try to flush back down to the pick up. Water should come out the intake openings in the lower unit. If all this checks out I would then pull the thermostat housing and check/replace the thermostat. If it is stuck closed or not opening fully the engine will not get enough water to cool it. Do all this and let us know what you find.
What was going on when you saw water leaking? Was it while running? What general area?
 
"The model # for my boat is 98

"The model # for my boat is 987343, I am about 99% sure it has a dog clutch. Ok to be honest I haven't seen the water coming from anywhere, I was on the lake the other day to test the "new impeller" I was on the lake maybe 15 minutes, when I got back to my trailer it had some minimal water in it...again not much but for being on the lake for such a small amount of time it makes me think water is coming from somewhere. I will bring it home from the lake tonight and do test on it and give you guys a heads up...man thanks for the help. The boat stay at the marine dry docked so I will let you know tonight what I am able to find out. If the T-stat isn't working correctly I am understanding correctly that it "could" close up and not allow water to cool the motor off?"
 
"Ok...that's the model for

"Ok...that's the model for a 1993 3.0 drive so yes you do have the dog clutch in the lower and the raw water pump in the upper. For the leak if you can't see anything obvious you need to be able to determine if it's coming from the engine or the boat itself, the easiest way of course would just to let the boat sit in the lake for a while without the engine running (after you dry up the bilge) Although it could still be water coming in through vents or ??? while driving the boat.

If your T-stat was closed up there no way you would have been driving for 15 mins without cooking that thing, what does the temp gauge say? Did you verify sufficient water flow from the impeller as Marada1 suggested above? Boat in neutral (in the lake) pull the input hose off the t-stat (have a bucket handy) turn the end facing up about level with the top of the engine, start it up and you should have between 2 to 4 inches of water coming out. Here is a cooling diagram for yours (may have to blow it up), it shows 2 variations depending whether you have power or mechanical steering.

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"
 
I will take my manual with me

I will take my manual with me tonight to locate the input hose....I am guessing not to hard to find but I can be an idiot at times....my luck I would pull the wrong one. Thanks guys
 
"OK brought the boat home last

"OK brought the boat home last night, I took the hoses off and noticed the hoses had some rust residue.....I am guessing this is help to m issues. Anyway I tried to clean everything as much as possible then hooked the drive up to my water hose and its now not overheating.....I haven't put it back in the lake...what are the chances it will over heat while under load?"
 
"There is still a good chance

"There is still a good chance you could have a problem. First of all running in the driveway puts no load on the engine so it doesn't ever really get hot, although if the t-stat was stuck closed that would show up eventually. The 2nd thing is that your providing cooling water under pressure which can mask problems with the raw water pump, true test is in the lake (or your neighbors swimming pool
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"I tried asking my neighbor ab

"I tried asking my neighbor about the pool thing and for some reason he said there wasn't enoug beer around here for him to let me do that....some neighbor he turned out to be. Well in conclusion I got the boat back to the lake and all turned out well.....the boat never reached above 170 and we were out there all day....so as for now it seems things are better but I will keep an eye out thanks for all the help, I will be back soon I am sure. Again thanks all!!"
 
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