Replaced Impeller/water pump parts, now motor won't run.

[mhieronimus]

I have a 1983 Mercury 25. The motor ran great, but I had decided to replace the impeller because I recently picked the boat up and didn't know what the past maintenance on it was like.

So I took the LU off, everything went pretty smooth (other than I discovered that my motor was originally a short shaft converted into a long shaft), got everything back together, put the motor in a tank and bam... won't start. It'll pop, seems like it want's to pop off and start up some times.

I checked spark, and have spark on both cylinders, tried fuel from two different tanks, the plugs are new as I replaced them when I got the boat. There's no leak in the fuel line, no fuel supply issues, and the inline fuel filter is clean as a whistle.

I'm dumbfounded because I didn't touch anything with the power head or related components that I remember. I just had to take the recoil off to get the shifting linkage disconnected to drop the LU.

Any help is greatly appreciated.

 

[SoCalBoatGuy]

Some kind of safety to keep it from starting in gear?

 

[flyingscott]

Did the motor run good on the lake?
How did you test the spark

 

[Texasmark]

So Carolina may have nailed it. 25 hp.....does it have a reverse lock? Are you trying to start it in gear? Did you test the prop to ensure that when you think it's in N it really is....aka when you put the linkage back you didn't have the shift dog in the LU in the same gear as you had the shift lever.

 

[flyingscott]

So Carolina may have nailed it. 25 hp.....does it have a reverse lock? Are you trying to start it in gear? Did you test the prop to ensure that when you think it's in N it really is....aka when you put the linkage back you didn't have the shift dog in the LU in the same gear as you had the shift lever.

Nope I can say with some positivity there is no problem with a shift interlock on that motor. They use a mechanical lock on the recoil to stop it from starting even if the lock breaks it will still start. That lower unit is pretty much foolproof for putting back together,the only time they get screwed up is after a waterpump change. Even then it's usually because somebody shoved the shifting cam in backwards. He has a different issue need more information.

Is there water on the plugs?
How did you check spark?
Is there to much fuel on the plugs?
Is the plastic linkages for the primer in good shape.

 

[flyingscott]

One more thing does it have electric start

 

[BLKBEARD]

try a little gas down the carburetor throat, maybe the float needle is stuck in the seat.

 

[mhieronimus]

Nope I can say with some positivity there is no problem with a shift interlock on that motor. They use a mechanical lock on the recoil to stop it from starting even if the lock breaks it will still start. That lower unit is pretty much foolproof for putting back together,the only time they get screwed up is after a waterpump change. Even then it's usually because somebody shoved the shifting cam in backwards. He has a different issue need more information.

Is there water on the plugs?
How did you check spark?
Is there to much fuel on the plugs?
Is the plastic linkages for the primer in good shape.

I can pull the recoil with it slightly in gear, and the prop moves the right way for forward, reverse, and neutral is in the correct position.


You're correct on the recoil stop.

I can't say I checked to see if there was water on the plugs.
Checked spark with a spark tester.
I also can't say that I checked the plugs to see how much fuel was on them
I'm not sure what plastic linkages you're referring to.
It's a pull start.

I'm at work and will have to check on the fuel/water tomorrow.

Did the motor run good on the lake?
How did you test the spark

motor ran great on the water, and in the tank prior to the impeller change.

 

[flyingscott]

Check the flywheel key

 

[mhieronimus]

So pull the flywheel off? What am I checking? That it's there?

 

[Texasmark]

So pull the flywheel off? What am I checking? That it's there?

Remove the flywheel nut and look straight down at the top of the crankshaft and top of the flywheel. where will be a ⅛" give or take square slot cut in each and locking the two together is a piece of square steel.....the Woodruff key. If it is deformed in any way, or any slop, it will affect your timing. On a Briggs 4 stroker, half sheared the engine won't even start.

The plastic could be the linkage plastic where the wire linkage is attached to something more rigid. The plastic breaks and gets sloppy with age.

 

[mhieronimus]

Remove the flywheel nut and look straight down at the top of the crankshaft and top of the flywheel. where will be a ⅛" give or take square slot cut in each and locking the two together is a piece of square steel.....the Woodruff key. If it is deformed in any way, or any slop, it will affect your timing. On a Briggs 4 stroker, half sheared the engine won't even start.

The plastic could be the linkage plastic where the wire linkage is attached to something more rigid. The plastic breaks and gets sloppy with age.

Thanks, still haven't had a chance to get at this. My days off start today so hopefully pretty soon here.