Alarm/Overheating maybe the result of head gasket failure

[mzmanley]

I wanted to post the following as the most plausible explanation of a recently triggered warning alarm and overheating condition.<br /><br />Patient: '89 200hp Yam (rebuilt), hrs since rebuild unknown.<br /><br />Symptoms: Alarm triggered, starboard cylinders running hot.<br /><br />Repairs: water pump (new), replaced T-stats & fuel pumps.<br /><br />Originally the overheating was attributed to a defective T-stat. In fact the starboard side T-stat was defective but after it was replaced the alarm was triggered again. With a new water pump, and recently replaced T-stats and fuel pumps the alarm went off a second time. Here is another plausible explanation - something not offered up as an explanation and something that I have not read on this forum regarding overheating motors.<br /><br />The faulty T-stat was responsible for the initial overheat but that likley caused an already weak heat gasket to fail. I noticed that the motor did not smoke when first fired up. I pulled the plugs and found water in two of the starboard cylinders. The head was pulled and sure enough those two cylinders were ingesting water. The crank has since become very tight (the motor has effectively seized).<br /><br />It appears that the reason the alarm was triggered the second time was the result of the compression and steam pressure leaking into the water jacket preventing the water pump from circulating enough water to cool the motor.<br /><br />FYI - It may be advisable that on older motors (or neglected motors) an alarm maybe the result of a failed head gasket. Breaking down the motor immediately may allow the motor to be saved. <br /><br />PS: this motor looks very good from the outside but the head gasket was in very poor condition. It maybe a good idea to reseal the heads once a year in salt water applicatins ($100 in gaskets, etc.). This was a '89 motor but it was rebuilt so the head gaskets must have been replaced.<br /><br />Does this sound reasonable?

 

[rodbolt]

Re: Alarm/Overheating maybe the result of head gasket failure

Hello<br /> one of the classic symptoms of a failing head gasket is it will overheat above 4000 rpm with good water pressure. I see quite a lot of head gasket failures. usually caused by some aftermarket head gasklets that I wont name by name. the metal in the gasket rusts away and poof no head gasket. takes 2 to 3 years and its gone.I no longer use aftermarket head gaskets in my rebuilds. got tired of having this failure and my customers looking at me to make it good which I did. I try to tell people that if your engine runs funky at the days end it is imperitive to look for water on the plugs. as in your case if you had seen the water the same day a headgasket job would have been ok. now you may need a crank,rod and pistons. and what is sad is the head gaskets still cost the same.<br />good luck and keep posting

 

[mzmanley]

Re: Alarm/Overheating maybe the result of head gasket failure

Thanks Rodbolt - Would appreciate your and others recommendations based on the following:<br /><br />This motor is in above average condition less the seized powerhead. I have done some research on replacing the powerhead, etc.<br /><br />What is the smart move from here?<br /><br />PS: I have all the powerhead bolts out but have not removed the powerhead from motor.<br /><br />Details:<br /><br />1. I can get a complete long block from Yamaha for $3,850.00 (no tax, not the typically quoted dealer retail price of $4,500) with an over the counter 90 day warranty. <br /><br />I suspect that setting up the carbs and other gaskets needed, including some mechanic labor costs will price out the new powerhead installed at $4,500 approx.<br /><br />Options:<br />1. purchase new (from Yam) powerhead with net investment of $5,000.<br /><br />2. purchase rebuilt PH and anticpate a $500 core value. Net investment $2700 to $3200 plus set up.<br /><br />3. I found a new in box 2001 200Hp HPDI for $9,700 (I assume this does not include gauges and rigging etc.) Can someone confirm if a new motor include hydraulic steearing etc.<br /><br />4. Have existing powerhead dismantled, inspected and potentially rebuilt by local shop?<br /><br />Please advise all - Many thanks!!!