1996 90 hp overheat warning

[twofarmers]

Sucked up silt enough to stop water flow for 10 seconds, overheat alarm sounded and I shut down the engine for a few minutes. When I restarted, the engine ran fine, water flow was fine, except for midrange, when the overheat alarm sounded again. Took it home for diagnostics. I have replaced water pump and thermostats. Runs cool at trolling and wide open speeds. Warning alarm sounds at mid range (2300 rpm). Runs great without thermostats. One mechanic says head gaskets, another says silt is still in head. Will compression check show the head gasket problem? Thanks in advance..

 

[rickdb1boat]

Re: 1996 90 hp overheat warning

Yes, a compression check would reveal a head gasket problem and you might have water getting into the cylinders, but I'm betting you still have silt in the cooling passages. Remove the lower unit and T-stat and flush out the system real well. Flush through the T-Stat opening and up through the water tube. Check out the impeller again. Check out the impeller housing for signs of scuffing. did you just replace the impeller or the whole pump? Including the housing?

 

[twofarmers]

Re: 1996 90 hp overheat warning

Thanks for the input. I've flushed the powerhead without the thermostats and flushed the lower unit when the water pump was replaced. I've run it about 4 hours in fresh water without the thermostats and the temperature is fine. Wouldn't a head gasket overheat? Can there still be silt after all this?

 

[Dhadley]

Re: 1996 90 hp overheat warning

There were 2 115's in 96. Which one do you have? <br /><br />The 60 degree models dont have head gaskets. Post the model number so we know where we are now.<br /><br />Good luck!

 

[twofarmers]

Re: 1996 90 hp overheat warning

Sorry for the confusion. This is a 1996 , 90 HP with the 90 degrees block..

 

[twofarmers]

Re: 1996 90 hp overheat warning

Yes, I replaced the entire pump housing.

 

[Dhadley]

Re: 1996 90 hp overheat warning

Ok, with a crossflow you do have head gaskets. And you have the rubber deflectors in the water passages too. I would definately pop the heads off, change the deflectors and head gaskets.<br /><br />While youre at it, its really no big beal to remove the water jacket cover on the heads and clean out those passages.<br /><br />Keep us posted!

 

[twofarmers]

Re: 1996 90 hp overheat warning

Thanks for the help..got the parts...trying to find the time..

 

[twofarmers]

Re: 1996 90 hp overheat warning

With engine almost warm, compression: 1=140, 2=140, 3=135, 4=140. Not enough difference to be a head gasket? Also, I let the parts store talk me into an NGK substitute plug when I put in the new water pump. Ever seen the plug make an engine run hot?..thanx

 

[Solittle]

Re: 1996 90 hp overheat warning

Compression is great. Don't know about the NGK plugs causing the motor to run hot but I do know that OMC motors run best with Champions and suggest that you replace the NGks. Check your manual for the right one or chech the red Search unless someone jumps in with the rignt one.

 

[twofarmers]

Re: 1996 90 hp overheat warning

Heading for the lake tomorrow for a test run. If it still runs hot, is there a way to clear the water jackets without pulling the heads. I hate to break a factory seal..

 

[rickdb1boat]

Re: 1996 90 hp overheat warning

Champion QL77JC4

 

[DJ]

Re: 1996 90 hp overheat warning

Lose the NGK's.<br /><br />Pull the heads, this is NOT a big deal. With an engine that age, I doubt the bolt torques are correct anyway.<br /><br />Take a close look at the deflectors, as Dhadley mentions. They can move or melt when they get hot.

 

[twofarmers]

Re: 1996 90 hp overheat warning

Pulled starboard head last night..easy, found no obvious problems. Do the deflectors get lubricated with silicon before pushing them in? Also, does the plate between the heads house any water jackets or just exhaust? I have the gasket for this plate and will probably pull it for cleaning and reseal.

 

[Dhadley]

Re: 1996 90 hp overheat warning

No NGK's. No silicone. <br /><br />Get the Champion QL77JC4's as Rick mentioned earlier. <br /><br />I spray the deflector with Electra Clean and they will slide right in.<br /><br />No KGB's!! I mean NGK's!!

 

[twofarmers]

Re: 1996 90 hp overheat warning

Both head gaskets are now replaced and correct Champion plugs are installed. Both water jackets looked like the bottom of the hot water heater. The local lake I fish has extremely hard water and it looks like it deposited in the water jacket and formed rocks. All are clean and I am waiting for one gasket to finish. Does the plate between the cylinders have any small water passages that need to be cleaned? Thanks again

 

[twofarmers]

Re: 1996 90 hp overheat warning

Thanks for all the help. New water pump, t-stats, head gaskets and water jacket gaskets. Ran it for an hour straight with no overheating. The key was cleaning the water jacket passages. Should be good for another 6 years.