1970 Mercury 650 running hot

[reds1963]

Hi to you all.<br />I have just brought a 1970 Mercury 650.I knew it had had water problems when I got it.<br />I have replaced the complete impoller unit,gaskets ,housing the works.Have also replaced the two gaskets in the exhust side of the motor.They where both blown.I have checked out the rings and things and all seem fine. We are getting a comp: of 120ps - 130ps from all three pistons.<br />I have back flushed the water system with a hose pipe and all seems fine. <br />The water still seems to get very hot.After taking it for a run only steam is coming out of the pee hole until i put it into neutral gear and let the motor cool down a bit and then we get a water flow again.<br />Is this normal for this motor ?? Or do I look somewhere else in the motor.<br />The only other thing I can think of is that someone has played around where the pee hoses on the engine block.With xmas just around the corner the boat shop whats nothing to do with it until the end of JAN:. Does anyone know or have a picture of where the water pipes should be running.<br />If anyone has any ideas it would be of great help.<br />MANY THANKS<br />NICHOLAS FROM NEW ZEALAND<br />:confused<br />

 

[Dunaruna]

Re: 1970 Mercury 650 running hot

Nicholas, you'll get a better response if you post under 'Mercury Outboard'. (is it a blueband hockey stick merc) Water only exits through the pee hole at low RPM, at higher revs, it exits through the center of the prop. The steam doesnt sound good, the pump impellors on these mercs can literally melt within minutes if it is starved of water. I know you are in the middle of summer holidays and can understand your urgency but dont cook you motor for the sake of another inpellor, check it again carefully. Good luck. Aldo

 

[bob58]

Re: 1970 Mercury 650 running hot

I have a 72 650 and water exits the peehole at all rpm ranges. Never just steam comming out.<br /><br />Did you get the impeller vanes turned the right way and key installed when you installed it?<br />If they were not , you could need to replace again.<br /><br />EDIT:<br />When you replaced the impeller, did the old one come out intact or were there pieces broke off.<br />the reason for asking is it is possible to have pieces of the impeller rubber restricting cooling water flow.

 

[moderator1]

Re: 1970 Mercury 650 running hot

Moving to Mercury/Mariner questions.

 

[mellowyellow]

Re: 1970 Mercury 650 running hot

as soon as crank turns, it will push vanes of<br />impeller in correct direction... as long as keyway<br />is correctly installed. try forcing some compressed<br />air through the pee-hole, could be a critter's<br />nest in there.

 

[rickdb1boat]

Re: 1970 Mercury 650 running hot

Steam is not good! Are you sure the impeller key was installed correctly, as Mellow suggested? Sounds suspicious as it returns to normal at low speed or idle. A clogged pee hole should not cause an overheat that quick. Sounds like the impeller is spinning free on the shaft when you throttle up and catches again when you idle. Pull the lower unit off again and check the impeller key again. Let us know what you find. Also, make sure the copper water tube is lined up correctly when you re-install the LU.