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View Full Version : having trouble again 350 chev alpha 1



clarke bayne
05-30-2002, 10:51 AM
motor overheats at idle 700 rpms. new pump in outdrive,new intake hose from outdrive to motor,risers removed checked for junk in manifolds, new thermostat.motor runs great at wot at any speed but idle. bought boat with 31 hrs on motor, but noticed on sea trail that boat ran cold at 110 not 165. asked owner he said he thought it was stuck. so i replaced it then came the headaches.at wits end in chesapeake bay. clarke. :mad: :confused:

Rootsy
05-30-2002, 11:37 AM
hmmmmmm sounds like a lack of coolant flow to the motor at idle and adequate when you give it some fuel eh... did you run the motor without water for even 30 seconds??? if so you need to check that impeller in the sterndrive again. How did the old one look when you removed it? missing pieces? if so you may have them lodged somewhere along the way... have you checked the hose from the transom assy to the circulating pump on the front of the motor? I assume the hose you replaced is the 12 inch long hose from the on the transom assy, if not then check that one cause it can delaminate. Sometimes the hose from the transom assy to circulating pump on front of motor will delaminate inside also. If there is an oil cooler inline with it then you need to check each side. i've also seen this condition if the shaft is turned the wrong way in the sterndrive when installing the housing over the impeller... also if the impeller housing has a crack in it, if there is a gasket leak or if the transfer tube from the impeller housing to the upper gear housing is cracked or the rubber seals is missing, i have witnessed where the one in the upper housing can get pushed up further where it won't seal the tube end. How bout the O-ring on the sterndrive mounting surface to transom ass'y. If it gets pushed out of place while installing the sterndrive it allows enough coolant to leak past and come out the prop instead of going into the motor... until you speed the motor up and it pushes more water than can leak past. Probably could investigate the circulating pump on the front of the motor... although there isnt much that can go bad in em cept a leaky seal which is more of a nuisance than anything. Lastly off the top of my head... the plastic retainer under the thermostat, is it installed correctly?

do the risers run hot at idle? can you lay your hands on them without becoming uncomfortable? how bout when you rev the motor up and hold it? Does the alarm sound at idle telling you of an overheating condition? What temp does it run at idle and at speed?

clarke bayne
05-30-2002, 01:19 PM
jamie root thanks for your help. to answer your good questions here goes. the plastic retainer in this motor is ethere cork or brass both new installed by merc tech. risers get very hot at idle cool right back down at 1500 rpms in 30 secs the alarm appears to be inoperative, also motor runs at 165 degrees at all speeds but idle. at idle motor has been as high as 195-200 before i've caught it. checking right now the other things you suggested. thanks for the help please keep fingers crossed. clarke.... :mad: