1969 Mercury 1000 lost #3 and #4 cylinder

[NJCinMN]

Hello all,

Motor had been running fine. Then on the lake the other day at WOT the motor justed dropped off and seemed like it was only running on a few cylinders and really smelled of gas. I covered top carb, motor died, covered middle carb, nothing, covered bottom carb, motor died. I pulled the plugs and all looked ok except #3 and#4 were pretty wet. I seemed to have lost spark on #3 and #4 cylinders. The ignition is a single coil with distributor. Any suggestions on where to start with the ignition would be greatly appreciated. Could it be as simple as needing new wires?

Thanks.

 

[Laddies]

Re: 1969 Mercury 1000 lost #3 and #4 cylinder

The chances of loosing spark on 3 & 4 at the same time are slim. inless one of the wire clamps that sre shared by them have shorted them out. You need to check the fuel pump diaphram and the carb for them they both will flood those 2 cyl.

 

[NJCinMN]

Re: 1969 Mercury 1000 lost #3 and #4 cylinder

Thanks for the advice laddies. I don't think it's the fuel pump as I just did a rebuild of both including new check valves however, i guess that also makes them suspect. I'm 100% sure they were assembled and installed correctly but I'll pull them to take a look. Do the replacement diaphragms break often (quicksilver brand)? The upper pump would be the one flooding these cylinders...correct? Could the new fuel pump be pushing too much fuel past a worn out needle and seat? Sorry for all the questions. Just trying to figure it out with my rational why I lost cylinders at WOT and have not gotten them back at any RPM. I'll double check the spark to see if I can rule out any ignition problems and you seem pretty confident that's not the issue. I'll repost tomorrow after working on it in the driveway tonight.

 

[Laddies]

Re: 1969 Mercury 1000 lost #3 and #4 cylinder

Yes, it's the top pump. if you used aftermarket kits to repair them, check the gaskets they won't be right the 18-7804 kits are for the older style pumps. As far as more pressure making inlets leak anything is possible

 

[NJCinMN]

Re: 1969 Mercury 1000 lost #3 and #4 cylinder

These are the rebuild kits I bought. I'm pretty sure these are correct. Looked identical to ones I took out.

21-30430A1
http://www.eastcoastmarineservice.com/fuelsys.html - fpkit

 

[Laddies]

Re: 1969 Mercury 1000 lost #3 and #4 cylinder

OK, I just checked and the fuel pumps on the 6 stayed the same it was only the large 4 cyl. engines that had some with differant gaskets on them.

 

[NJCinMN]

Re: 1969 Mercury 1000 lost #3 and #4 cylinder

Ok. Here?s what I've got. I checked each spark plug with its respected cylinder and have great spark on all 6. I pulled the top fuel pump to check for leaks, etc. and all looks good. I also did the test and pulled the fuel line that goes to the top carb and it has sufficient flow. To recap, I have major oil/wetness on #3 and #4 cylinders and a lot of unburned oil around the exhaust/propeller. I guess all that?s left is the carburetor. Stuck float?? Laddies thanks for the help and let me know if I'm on the right track or if you have any other suggestions. Thanks again.

 

[Laddies]

Re: 1969 Mercury 1000 lost #3 and #4 cylinder

For sure you have a carb problem, bad inlet, wrong float height or spring height, a saturated float will also cause a leaky inlet needle.

 

[NJCinMN]

Re: 1969 Mercury 1000 lost #3 and #4 cylinder

I took all three carbs off last night and the appropriate parts are soaking. I'll let ya know how she runs when I get them back on and do the link and sync.

 

[NJCinMN]

Re: 1969 Mercury 1000 lost #3 and #4 cylinder

This old motor still rips. Had it out the other day and was averaging around 40 mph at WOT with myself and a friend in the boat. It climbed right out of the water and got up on plane almost instantly. I'm still trying to find the sweet spot for the idle screw adjustment but no complaints.

 

[bchoate]

Re: 1969 Mercury 1000 lost #3 and #4 cylinder

I"m glad you still have it running.
I love the ole "Tower of Powers" Good luck with it.