Ran out of Fuel now engine won't Idle..... Need Opinions.....

[chadpcb]

First go ahead and say it.... Put gas in it.....

Was not a intentional run out of fuel....
I have 2 tanks on my Mako with Merc 350 5.7l Carbed(Quad)
I have always used my P tank for coming back in and my S tank for going out.
For some reason this passed saturday I ran on the P tank going out and the S tank coming.
When I hit a quarter of a tank on my P Tank, I switched over to my S tank.
I ran for about 2 miles and engine died.

So I tried to crank the boat and nothing...
Checked fuel and filters was empty..
Switched back to P Tank and nothing again...
engine will not crank.

Call Sea Tow and get towed in.

Oncw on the hill I started to look over the issues.
What I discovered.
1. Dry rotted fuel lines from 1981
2. No Fuel in lines.
3. bad fuel valve on S tank line

Remedy
1. replaced all fuel lines from tanks to filters
2. Pulled all 3 filters cleaned, refilled with fresh gas.
3. built a new fuel valve assymbly with shut offs on each tanks

Outcome
Engine will start and run. But doesn't idle below 1200 Rpms


Any help would be greatly aprreciated

Tha ks
Chad

 

[NHGuy]

Does it stall when you lower the RPM? Or have you not tried yet?
To turn it down to the desired 725 in neutral start it up, then with a screwdriver turn the speed adjust on the port side of the carb counterclockwise til it goes down to a speed you desire for warm up. Maybe 800 or 950.
Once warm. turn it down to 725. If it won't run that slowly it could have one or two likely issues. It could need the idle jets adjusted, and/or it could need a cleaning if dirt came up the supply line. Thankfully you have filters. You did not mention changing the water separator/filter, make sure you do. Even if it looks good it can have microscopic particles or holes. Cheap assurance. There's also one last fine screen where the fuel enters the carb, remove and clean that.
There are lots of posts on how to set up the idle jets. If you need the info we can go through it for you.

If you need to understand why, the old poor fuel lines could have allowed some air into the fuel supply, now that the fuel is air-free the carb may need different settings.
And if it turns out to be dirt, well dirt happens in lots of ways.

 

[Scott Danforth]

my first thought is that the deteriorating lines and crud made it to the filter and the idle circuits are plugged.

 

[superbenk]

Sounds like you need a carb rebuild with thorough cleaning. You likely picked up gunky gas, residue & other junk when the tank ran dry and sucked it into the carb.

 

[superbenk]

Also consider replacing fuel filters.

 

[gm280]

I have to agree with the previous assessments. You stated how bad the fuel lines were and that points to problems with trash making it to the carb. I see a carb rebuilt in your future...

 

[chadpcb]

Nhguy

Filters are a little over a month old. There is three filters. One main fuel water separator on main fuel Line then secondary filter on engine starboard side by circuit breaker. Then of course the carb filter. These get changed every April 1st.

You mentioned idle. When I crank the engine up I have to give it gas to keep it running. 1200 rpms. If I back off the throttle and put it in neutral position the engine dies.

 

[Bondo]

Ayuh,.... Fuel filters can be junk the day they're installed if the fuel goin' into it is fulla water, 'n crud,.....

That's Why I always suggest inspectin' the Contents of fuel filters, insteada just tossin' it into the trash,.... an Important diagnostic tool,...

If it don't idle, Odds are water, 'n crud has already gotten into the carb,.....

 

[chadpcb]

Ok so its been 15 days since I replied. I have figured out the issue.

1. Both primary and secondary filters was slap full of water.
2. Primary filter was full of debris
3. Washable filter in carb was lets say just nasty.
4. Rebuilt carb. Idle section was completely clogged.

Now she idles at 750 and purrrrssss like a kitten on steriods.....

Thanks for all the advice......

 

[Bondo]

Ok so its been 15 days since I replied. I have figured out the issue.

Ayuh,..... You've been Busy,..... Thank you for the update,.....