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Possible timing issue

M

Mercury81

New member
Hi everyone,

New here and I recently picked up a boat with I believe a 1981 Mercury 25HP motor on it. Motor ran well, but I decided to replace the impeller. I purchased a full water pump kit, replaced the parts, got it all back together and now it doesn't want to run (doh!).

When I got it all back together after about 6 pulls it wanted to, but that was the end of it.

I noticed several dots on the flywheel. I'm assuming these are some kind of timing marks. I had to take the recoil off to get the throttle disconnected, and when reassembling the lower part of the motor I had to move the flywheel by hand to get the teeth on the drive shaft to mesh. Would having the recoil off and turning the flywheel by hand change anything with the timing? I know probably a fairly dumb question, but I'm a little stumped why it won't start.

Thanks!
 
That's not the cause of your motor not starting timing has not changed, You need compression,spark& fuel for it to run Are u using proper starting technique, squeezing primer bulb,fast idle adjustment,choking till warm, Is vent open on tank, Does primer bulb firm up before starting Are plugs clean? Is engine in neutral before starting ? Is there a lanyard,is it installed correctly?Kill switch?
 
I figured not. Yes. I'm using proper starting technique. It really sounds like it wants to, but just can't get it to fire off. Only thing I can think of is that I checked the fuel filter (inline) and the o-ring from that seems to be missing and it's sucking air through the top of the filter canister. I'll throw a new O ring in there tomorrow (if I can find one) and give it a shot.

The motor ran beautifully a couple days ago before I tore it apart. Hence why I'm kinda stumped on this.
 
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If that o-ring "gasket" is missing,primer bulb would never firm up,air leak. Are we talking about water/fuel separator? Shaped like a oil filter?
 
My 87 Merc was doing the same thing. I used a spark tester on the plugs and found out cylinders 1, 3, & 5 had no spark. Replaced the upper switch box and it fired right up.
 
I replaced the O-ring. It was on top of the fuel filter assembly (see link)

https://www.marineengine.com/parts/mercury_marine_parts/sn/06417102/ 1025203/676_6

So I replaced this so there's no leak in the system, and same deal. It'll pop here and there but it doesn't want to fire off. Checked the spark and have spark on both cylinders.

I'm kind of dumbfounded at this point. There has to be something that I missed.

Motor ran like a top before, took the LU off and replaced impeller and related parts. Reassembled, goes in and out of gear just fine. I didn't touch anything with the carb or electrical system.

Also, the kill switch is built into the throttle/shifting handle. It doesn't have a clip that holds it out, it's just a push in kill switch. Plugs were also replaced 2 weeks ago when I got the boat.
 
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Are you using an open air gap spark test? Grounding plugs to block doesn't work, not a proper test. I would test compression on all cylinders
 
No, I'm using an actual spark tester. I'll see what I can do about the compression test tomorrow. Not sure why suddenly the compression would have gone to heck?
 
We are just eliminating one thing at a time",troubleshooting" Your thread said "i had to remove the recoil off to get the throttle disconnected." What throttle was disconnected?
 
johnnygjr said:
We are just eliminating one thing at a time",troubleshooting" Your thread said "i had to remove the recoil off to get the throttle disconnected." What throttle was disconnected?
Click to expand...

Yeah with this particular motor it's easier to remove the recoil to disconnect the shifting linkage. Throttle handle is also the shifter on this one. Throttle wasn't disconnected, just the shifting linkage.
 
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