Boat sat for 2 years ~ Won't Stay Running (Mercruiser 3.0)

Hi everybody,
I recently bought a boat for super cheap that hasn't been run in two years. It's a 1986 Mercruiser 140/3.0 with an Alpha One. The previous owner removed the floor and gas tank and re did the stringers, so there was no gas at all left in the tank.

I've aligned the engine and replaced the water pump, changed the oil and filter, gear lube, rebuilt the carb, and put gas in it. I pulled the distributor cap and checked it for corrosion and checked the points and they look alright.

I went to start it and cranked for awhile to get the gas up to the carb and once it reached the carb I gave the throttle a couple pumps to get gas into the engine. It started but then puttered out about 2 seconds later. I tried to start it again, but it wouldn't fire at all. I pumped the throttle again and it started for a few seconds and died. I kept trying this, but it kept dying. I checked the idle speed adjustments and the mixture and it all seemed good. I pulled the carb and check the float levels again and they are exactly where they should be, so I tried to start it again and the same thing happened. This time I gave it a 1/4 throttle and it started and continued to run, but a bit rough. It didn't die, but I wasn't comfortable running it at 3000 rpm on muffs so I backed it down after about 20 seconds. When it got to about 2500 rpms it died again and I had to pump it to try and start it again. It acts like it's running out of gas, but I'm not really sure where to start diagnosing this issue.

Also, I've tried running it without the fuel cap on to make sure it was not a vent issue, and it was not.

Any help would be great! Thank you!

Re: Boat sat for 2 years ~ Won't Stay Running (Mercruiser 3.0)

How did you determine your idle mixture screw(s) was(were) set correctly?

Sounds like no fuel is making it through the idle circuit. (the mix adjustment screw is for the idle circuit, main circuit is adjusted by changing jets)

Is the choke working correctly?

Re: Boat sat for 2 years ~ Won't Stay Running (Mercruiser 3.0)

Sorry I should have said that I set the idle mixture to what it was when I got the boat (out 2.25 turns).

I will go check the choke and get back to you. Thank you!

Re: Boat sat for 2 years ~ Won't Stay Running (Mercruiser 3.0)

The choke plate was not fully working, but I adjusted it and now it stays closed or close to closed when the engine is totally cold. The engine started like normal, but as the choke opened more, it started to die. How long should it take for the choke plate to open? And should the choke continue to open/keep heating up when the key is turned on, but the engine is not running? It almost seemed like the choke plate was opening too soon.

Re: Boat sat for 2 years ~ Won't Stay Running (Mercruiser 3.0)

Again, sounds like little or no fuel through the idle circuit.

Yes, the choke should slowly open as long as there is power applied to it...
It should be closed with a little bit of spring tension when stone cold.
Sounds like you have it right now...

Back the idle mix screw out 1/4 turn at a time and see if that helps.
Sometimes the exact spec from a brand new carb doesn't apply to an old one that has build up in the passages... Even on a new one, the spec is just a starting point.
Should be adjusted for the best idle IN GEAR, IN THE WATER. (See the adults only section).
You can get close on the muffs and then take it to the water to fine tune it...

This all said, you are using the throttle only button and giving it some throttle for the first couple minutes, right?

Re: Boat sat for 2 years ~ Won't Stay Running (Mercruiser 3.0)

I was able to keep the engine running if I held the choke plate about half way, so it is definitely a fuel issue. I started at the tank and checked the pick up, check valve, fuel line from tank to pump, fuel pump filter, the filter on the carb, and nothing has looked out of the norm. I already tried backing out the mixture and it didn't change anything, I went out probably another two turns.

Yes, I had it in neutral and I was giving it gas and trying to warm it up, but I have to keep it at 3000 rpm to keep it running and I wasn't sure if that was a good idea to run it like that on muffs.

How do I check/clean/fix the idle circuit? Thank you!

Re: Boat sat for 2 years ~ Won't Stay Running (Mercruiser 3.0)

Nope...won't last long at 3000 on muffs. Time for a carb rebuild, sounds like it is gunked up from setting without fuel treatment.

Airshot

Re: Boat sat for 2 years ~ Won't Stay Running (Mercruiser 3.0)

The carb is soaking in berryman's right now. I'll finish cleaning it and reassemble it tomorrow and post back. Thanks!

Re: Boat sat for 2 years ~ Won't Stay Running (Mercruiser 3.0)

The carb parts are soaking, or did you just put the carb in whole? Not everyone who reads this will know the difference, just sayin'...

Re: Boat sat for 2 years ~ Won't Stay Running (Mercruiser 3.0)

The parts are soaking. I fully dismantled it, removed all of the gaskets, and put it in some carb cleaner. Sorry.

Re: Boat sat for 2 years ~ Won't Stay Running (Mercruiser 3.0)

Good deal Not all researchers that read this understand carbs and could think there is an easy way to fix a "dirty" carb!

Re: Boat sat for 2 years ~ Won't Stay Running (Mercruiser 3.0)

Fuel for thought: have you verified that your timing is correct?

Re: Boat sat for 2 years ~ Won't Stay Running (Mercruiser 3.0)

That fixed it! Something must have gone wrong in my first carb rebuild, but now it's running! It's running a bit rough, but I think I need to go through the ignition system and tune the engine up and then see how it's running. Thanks guys!