1984 Mercury 35hp. stalling in idle and trolling speed.

[HTG]

This engine has been running excellent for a few seasons now. Wanted to do a test run before takeing it out a few weeks ago and it ran just perfectly. Then I went to full throttle for a few seconds and noticed the boot hose came off so after I put that on I tried it again, went to full throttle for about 10 seconds and then it made a sound like it missed. The one mistake that I made was that the gas only had half the oil that it should have had. After that happened its having trouble starting and its dieing out in idle. The main reason is because there isn't enough gas in the line but I'm wondering what could cause this other than the hose or gas tank?

I took it out today and it will run fine just above trolling speed and at full throttle. Could I have fouled a plug when I was running it at home with the wrong gas mixture and would that have anything to do with this problem? My question is why is it running out of gas at idel, trolling speed and when I try to start it after it has been sitting for over 1/2 hour on the water? I'm planning on changing the plugs but I'm just wondering what else I can check? S/N 6578665

 

[HTG]

Re: 1984 Mercury 35hp. stalling in idle and trolling speed.

ttt

 

[HTG]

Re: 1984 Mercury 35hp. stalling in idle and trolling speed.

Could this be a fuel pump issue? Does anyone know where I can find instructions on how to change the fuel pump for this engine?

 

[HTG]

Re: 1984 Mercury 35hp. stalling in idle and trolling speed.

Could this be the impeller?

 

[oldman570]

Re: 1984 Mercury 35hp. stalling in idle and trolling speed.

When runnig a motor on muffs they should never be reved more than a fast idle as the motor has no backpressure on it and will over rev and damage can happen. If the water pump impeller is more than 3 years old it should be replaced. Not enought oil can also cause damage by scoreing the pistons and cylenders. Best bet is to run a compression test and check impeller if run for more than 15 seconds without water or no tell tail water.

 

[HTG]

Re: 1984 Mercury 35hp. stalling in idle and trolling speed.

Thanks I'm planning on replacing the impeller. I think its about 6 years old and probably broke when it was testing it.

 

[HTG]

Re: 1984 Mercury 35hp. stalling in idle and trolling speed.

I found out old gas caused most of the rough starting and idleing problem it was having. With new gas it runs good up to full throttle but its still having trouble starting and its still cutting out at idle. About 1/4 of the time it will start normally now on the water. If I put the throttle into neutral just a little bit it will start perfectly. What could be causing this starting idleing problem? Or what do I need to try to adjust now?

 

[oldman570]

Re: 1984 Mercury 35hp. stalling in idle and trolling speed.

Have you run a compression test on the motor to see if any internal damage was done when the muffs fell off? You could have scored a piston and cyclender or bgroke a ring . The fuel pump has to have good vacume in the crankcase inorder to pump fuel as it should. A bad compression reading should show up if the reading is to low on one or both pistons. A readig below 100 or a diffrence of 10% means something is wrong inside and needs to be fixed.
Oldman570

 

[HTG]

Re: 1984 Mercury 35hp. stalling in idle and trolling speed.

I don't have a tester yet but have been planning on getting one. Still trying to figure out what else I can check? Thanks

 

[Mi duckdown]

Re: 1984 Mercury 35hp. stalling in idle and trolling speed.

Check the compression first, so you are not chasing your tail.