Mercury 9.8 problem

[Coldtrain_1]

Ok, I have '72 Mercury 110 Thunderbolt 9.8hp. This motor has been sitting up for over ten years and I decided to get it from my grandfather and get it running. I have rewired everything and replaced the impeller, and other minor cleaning.

I started it today and is seems to be backfiring. I can start it and it will run, but it sounds like it is backfiring. It is a loud thumping sound, and it will hit so hard that it kills the motor.

What could be wrong? When I put it in gear, it seems to bog down and kill itself out, all the while, backfiring or whatever it is doing.

What are some suggestions on how to fix this?

 

[mla2ofus]

Re: Mercury 9.8 problem

Just a WAG, could the plug wires be switched?
Mike

 

[Coldtrain_1]

Re: Mercury 9.8 problem

Nope, One wire is just long enough to reach the #1 cylinder, and the other one reaches the #2.

 

[sschefer]

Re: Mercury 9.8 problem

Nope, One wire is just long enough to reach the #1 cylinder, and the other one reaches the #2.

When it's running and you put it in forward gear is the prop rotating clockwise? These little guys have been known to start and run backwards if they're carboned up badly. Just another SWAG.

 

[Coldtrain_1]

Re: Mercury 9.8 problem

Yeah, it is turning normally. If i put it in reverse, I can get the RPMs to come up, but if I put it in forward, it will continue to pop/backfire, bog down and ultimately cut off.

 

[sschefer]

Re: Mercury 9.8 problem

Why don't you try decarbing it with a can of SeaFoam in 1-3/4 gals of gas mixed 50:1 with TCW-3 two cycle oil. Run it for 15 minutes, wait 15 minutes and repeat two or three times then go back to fresh 50:1 mix in a clean fuel tank making sure the vent on the tank is working properly.

 

[lindy46]

Re: Mercury 9.8 problem

Did you have the flywheel off? Did you properly re-torque the flywheel nut? Possible sheared key.

 

[ENSIGN]

Re: Mercury 9.8 problem

Why did you re-wire it and what did you re-wire???

 

[Coldtrain_1]

Re: Mercury 9.8 problem

Thanks for everyone's input. But I figured out the problem. After replacing plugs, cleaning and rebuilding carb, we tried the points. I took them out, filed them with a dye grinder, and replaced them. Motor runs like a champ now.

I had to rewire the motor because all of the coating on the wires were falling off. Also the wires were corroded and falling apart. So I had to put new wires from the kill switch, from the points, and every other large wire on motor.

 

[ENSIGN]

Re: Mercury 9.8 problem

Glad you got her running! I was just wondering if you had some wires crossed.