My little merc let me down at the worst time

[mogfisher]

So I decided to show the wife how much fun the little boat is and show her some real fishing. The motor had different plans. She still had fun though but she laughed at me. She caught her first largemouth! Must have been at least a pound!

Its a 1983 18HP mercury belgium motor. It has run great for me all year so far. I added 2 gallons of gas and 6 oz of oil today. Motor ran great for a 15 minute WOT run after about a 8 minute warm up. Then we got to the other side of the lake and had to go through a channel and under a bridge. Putted fine through it until the end. After about 5 mins of idling through it skipped. I almost thought I hit something but then it did it again and again. Finally it quit. After some encouragement it started back up and got us to our spot at about half throttle about 5 more minutes. If I attempted anything more than half throttle it fell on it's face and sputtered.

We fished for about an hour and decided we needed a new spot and that it should be closer to the launch. It started ok (not great) but would still not go past half. Once we got back through the channel it died. It would start but stop immediately. i tried the start stall thing for 10 minutes before I decided my arm had enough yanking and we headed home on the troller. About half way back (30 minutes or so) I decided to try the motor again. It started and would go to half throttle. Towards the end if I gradually got on the throttle it eventually went up to full speed but would sputter and skip just a tad. I decided not to push it and just putted back to the launch.

What I have done so far to troubleshoot.

1. Verified that butterfly is opening when appropriate
2. Checked that bulb is hard
3. Checked spark plugs. Look same as usual but are maybe a bit wet
4. checked for loose wires
5. Opened filter housing to look for chunks. None found. Looks clean.
6. Verified a good pee stream
7. looked into spark plug hole at what I could see of cyl walls. Looks OK and compression feels same on the rope.
8. drank beer and scratched head.

I have since drained some gas into a clear jar to look for water settling out. It did rain since my last run and my boat sleeps outside. It has a portable tank with the vent in the cap and the cap likes to collect water. I'm hoping for bad gas but would that allow half throttle operation?

When it does run it seems like half throttle is normal but it does not idle as well as it should.

Any help is appreciated! Thanks!

 

[arsenalpsu]

Re: My little merc let me down at the worst time

If you have spark & compression than you're missing fuel somehow. If you have an in-line fuel filter replace it and rebuild the fuel pump. Both easy to do. If this doesn't work you'll want to clean the carb.

This is assuming you have good spark at WOT....

 

[mogfisher]

Re: My little merc let me down at the worst time

Problem solved. Sure did seem like fuel delivery to me but it appears that it was not. The 2 wires leading to the kill switch had chaffed off their insulation and must have been touching when the motor torqued or vibrated too much. Today, with the motor in a bucket after installing an inline water/fuel seperator, it would start and immediately stall. Over and over. I disconnected the ground lead to the block that goes to the kill switch and it immediately started and ran fine! So i pulled the wires out and put some liquid electrical tape on them, then taped them up and its good to go. I did however still decide to pull the carb apart and give it a good cleaning and rebuild the fuel pump in an attempt to get it to idle better. This motor has never idled well. I'm hoping that helps.