Mercury 650 re-starting problem

[Troy_from _Oz]

Hi, I have an old (70-72?) mercury 650 4-cylinder which seems to run really well- most of the time. It generally seems to start easily, even if left for a few weeks. <br /><br />The problem I am having it that when I stop the motor, then try to restart in quick succession, the motor will fire up - initially, then either die after a few seconds, or when I put the motor into gear. I can sometimes get the motor to continue to run if I shift into gear aggressively. If I try to do this softly, the motor dies. It is then difficult to restart.<br /><br />Compression is 130psi +/- 2psi (good but possibly indicating carbon build up?). Spark plugs are brand new.<br /><br />Any help would be greatly appreciated.<br /><br />Many thanks - Troy

 

[mellowyellow]

Re: Mercury 650 re-starting problem

cheers Troy,<br />this sounds to me like a fuel/carb. problem.<br />does the primer ball stay hard? if you pump<br />the bulb, does gas leak from the front of the carb?<br />my guess is floats sticking.<br />good luck,<br />M.Y.

 

[Troy_from _Oz]

Re: Mercury 650 re-starting problem

Thanks mellowyellow, I'll give it a go and see what happens.<br /><br />Cheers<br /><br />Troy

 

[RICKRICK1]

Re: Mercury 650 re-starting problem

T from Oz<br /><br />You might want to get new fuel pump diaphram(s) and change them also, had a similar problem and upon replacing the diaphrams I found a pin hole in it, motor would start and shift into gear fine when bulb was pumped up but would die after starting if I didnt pump the bulb.

 

[RICKRICK1]

Re: Mercury 650 re-starting problem

T from Oz<br /><br />You might want to get new fuel pump diaphram(s) and change them also, had a similar problem and upon replacing the diaphrams I found a pin hole in it, motor would start and shift into gear fine when bulb was pumped up but would die after starting if I didnt pump the bulb.<br /><br />

I fish, therefore I lie.

 

[RICKRICK1]

Re: Mercury 650 re-starting problem

ops sorry about the double post

 

[Troy_from _Oz]

Re: Mercury 650 re-starting problem

Thanks, Ill have a look into that too. Repair manual will (hopefully) be arriving this week, so I can they start to investigate with a little more confidence soon. (confidence that I know what it is that Ive broken after I have broken it ;-)<br /><br />Cheers<br />Troy

 

[rickdb1boat]

Re: Mercury 650 re-starting problem

Check fuel filter and lines going to it.

 

[Hooty]

Re: Mercury 650 re-starting problem

When you shift into gear, shift with authority rather then gently. Your clutch will last a lot longer.<br /><br />c/6<br /><br />Hooty

 

[Rex]

Re: Mercury 650 re-starting problem

What is your RPM at idle?<br />Check your idle timing.<br />and check your slow idle mix. on your carb.<br />Sound like when the engine warms up that<br />you may be running a little lean.<br />Just turn the idle mix. 1/4 turn out and see<br />if that helps.

 

[Troy_from _Oz]

Re: Mercury 650 re-starting problem

Thanks Rex.<br /><br />Unfortunately it doesnt have a tacho so I cant say what rpms it is doing at idle. I do have an Auto multimeter/tacho, so Ill try that. It does tend to idle a bit fast. Would that be the idle mixture when warm? Now that I have a manual, I can start to have a go at tuning it. <br /><br />rickdb1boat: new fuel filter. Havent checked the lines but will do. thanks <br /><br />I asked the local spares guy/mechanic when I was asking for a price on a carby kit for it and he said that it could be the primer bulb (not being vertical?) allowing fuel to drain back into the tank when it sits for a while. This seems to follow what RickRick was saying too. Any thoughts?<br /><br />many thanks for all your help and suggestions - Troy

 

[rickdb1boat]

Re: Mercury 650 re-starting problem

When that happens, pump bulb. See if it goes. My '67 did that, I cleaned Carb. and all was well. I always had a "Slick" of fuel on the Water, too, after stopping. That was normal, though! Also, might try tapping on carbs. with the handle of a screwdriver to free float. That was my problem when I rebuilt it. Needle was sticking! Vertical bulb will not have anthing to do with it, unless check Valve in Bulb it bad. Good Luck,

 

[Rex]

Re: Mercury 650 re-starting problem

It could be running lean when it warm's up.<br />That could cause it to idle high.<br />Rex

 

[Rex]

Re: Mercury 650 re-starting problem

Check out about the 5 degree timing being slow<br />on the other post-it.<br />Rex

 

[Hooty]

Re: Mercury 650 re-starting problem

You can get yourself a tacho for about $30 US at <br />www.tinytach.com<br />Don't know how you'll get it ta Oz though.<br /><br />c/6<br /><br />Hooty

 

[Troy_from _Oz]

Re: Mercury 650 re-starting problem

Thanks for all the suggestions. Finally got to have a look at it last night.. Pumped the bulb to check if fuel comes out of the front of the carbies (mellowyellow's first suggestion?). I guess this checks for sticking float? No problem there Im afraid. Will adjust Idle mixture and see if that helps when next out on the water and will try tapping carbies to see if this is the culprit when im on the water. Thanks again!!! T

 

[Troy_from _Oz]

Re: Mercury 650 re-starting problem

Rex A. H. - which post was it you were referring to about the 5 degree timing? Thanks T

 

[Rex]

Re: Mercury 650 re-starting problem

That the name of the post-it.<br />5 degree slow timing.<br />I know I should of put down mercury between<br />1967 to 1974.<br />It give you the page numer and the serial NO.<br />If you got your serial NO. just e-mail me<br />and I will tell you if it happen to your engine.<br />Good Luck with you engine.<br />Rex A.

 

[lennyox]

Re: Mercury 650 re-starting problem

When i turn my key on without starting my motor kicks, when i try to start it, it fires and dies like it backfires, I just rebuilt the motor and it was running OK, but was not charging battery so i checked the stator it had a broken wire replaced it and when i started it up again i had this problem plus i here what sound like spark from coil and coil lead, i disconnected the rectifier to see if that made any change "but no" could my coil be on its way-out, or maybe plugs braking down its a 1976 65hp 650 mercury. PLEASE I NEED HELP running out of options.p.s "new to the site"