1996 Mercury 225 Saltwater overheating

[abacoguy]

runs great. WOT 5400. However in above 80 degree water, overheats warning sounds every 10-15 min. of running. Have to wait for cool down. Changed impellers 2 times. changed poppit valve. 3 Mercury mechanics bewildered. Motor pees strong, but low pressure (5lbs max) since new. No obstructions on intake, motor on bracket. any ideas?

 

[valmet]

Re: 1996 Mercury 225 Saltwater overheating

abacoguy, have you checked the actual powerhead temp. with a heat stik at the time the temp. alarm sounds? maybe the temp. sender unit is dodgy.

 

[shelbydriver]

Re: 1996 Mercury 225 Saltwater overheating

maybe you can use one of those laser temperature gadgets too. sears

 

[abacoguy]

Re: 1996 Mercury 225 Saltwater overheating

Thanks for the idea on the temp sensor. One of the mechanics tried a replacement sensor and still had warning occur, put my old sensor back on. I think it is a true overheat since I have seen steam behind motor when running at speed.

 

[BW23]

Re: 1996 Mercury 225 Saltwater overheating

The only thing left is the thermostats. I have a 97 225. What does the popit valve do and how often should you replace it??

 

[jim dozier]

Re: 1996 Mercury 225 Saltwater overheating

Keep looking for the problem and post an answer if you find it. I have a similar ghost overheat problem on an 87 Suzuki DT85. Until you find the problem back off (retard) on your ignition timing ~2 degrees which will lower the WOT temp and give you a buffer until you can find the true fix.

 

[clanton]

Re: 1996 Mercury 225 Saltwater overheating

You need 12 lbs of water pressure at 5500 rpms.

 

[abacoguy]

Re: 1996 Mercury 225 Saltwater overheating

jimd:<br /><br />Thanks for the ignition retard suggestion until I find the problem. I'll keep you posted on the results. Thanks also to Clanton about the 12 lbs of pressure. Any idea where the pressure leak is or could this be a calibration error since I've never had more than 5 lbs since new in '97?<br /><br />Determined to Find the problem<br /><br />Abacoguy

 

[clanton]

Re: 1996 Mercury 225 Saltwater overheating

Post this problem on WWW.screamandfly.com. ther is problem with a plate under the powerhead on some v6s that causes overheat. You should be checking the temps with a melt stick or one of the new laser point and read temp checks. Important to insure alarm system is working correctly. Faulty alarms leads the list of problems for Merc and OMC.