possible fuel issue?

[MN John]

This is the fuel system post, for the issue I have been having, I also made a post for the igntion system, same issue.

the motor will intermittently lose all power, fire a few times sporadically and then run fine. Sometimes it will be bad enough to stop motor and it has to be restarted and then runs again. I have had this happen right after starting at times and sometimes after it has run for awhile. I only lose rpm on gauges all other gauges are still reading like ignition switch is still on. When it is running, its running good, and no change in gear or in idle.

While trying to chase this down I have done quite a bit, and I will try to cover only the fuel system in this post. (I am kind of new to forum, hope I am doing this correctly)

I run ONLY no ethanol fuel, when winterizing I filled tank and added stabilizer. I only add fuel 5 gallons at a time from a clean container. The tank is aluminum 20 gal. 10-15 yrs old. I run RACOR water/fuel seperator right after tank(above tank), 3' run downhill to elec. fuel pump, then to fuel pressure gauge, then polishing filter to carb.
After issue started, I replaced Racor, tank vent line, polishing filter, added fuel pressure gauge, polishing filter, and rebuilt/ cleaned carb twice. This may be related so I will add that the plugs used to get dark carbon build up fairly quickly and looking through spark plug holes there is a good amount of build up in there also, so I set idle mix a full turn more counterclockwise to lean fuel and plugs have gotten much better. All of this seemed to make the issue better, but not completely gone just less frequent.
I got ahead of myself and messed with igntion, electrical, exhaust and fuel at the same time (i now understand this is frowned upon) so I cant put my finger on the exact problem or have I been able to solve the issue.
When it is hesitating/dying I still have 3 1/2 to 4 psi? on fuel gauge.
There is a kind of loud sound coming from carb when running, like if u were blowing into a straw and very quickly covered and uncovered the end. I thought this was the sound of debris in a jet, but I now think it is the scavenge tube picking up a bit of fuel in throat?
The issue is still intermittent after all this, but seems to be getting better.
I am leaning towards fuel system but have not ruled out igntion, elctrical, or possibly even exhaust system? I will add pics and I am sure I forgot to add some info that I have come up with. any advice or help is greatly appreciated!

[JOHN COOKSON]

Water in the fuel is a possibility. Have you tried running off an auxiliary tank with known clean gasoline in it?

TRUE GRIT

[MN John]

No I didn't even think of it. guess I missed the obvious, and had more faith in the Racor then I should have. Now that I consider it we have had major rain storms for over a month, maybe deck fill or vent let some in. I will get a outboard type tank set up and bring it down to the boat next time. test tank straight to carb or run it thru filters and lines from main tank?
Reading a couple other posts about air suction leak or vapor locks, its all very interesting. Never had the pick up tube out and saw mention of that as well.
This is maybe irrelevent but it has been so hot and humid lately that alot of condensation beads up on the outside surface of carb to intake manifold connection, just like a glass of ice water, could this possibly be a source of water contamination besides upstream source, tank etc.

[prstack7]

water in gas

Water in gas sounds possible. Using a hand pump, pump out a little from the bottom of the tank into a glass and check for drops. Check the O ring on the fill cover. I would have saved myself a lot of changing of items if I had done this first.

[JOHN COOKSON]

MN John
Have you ever tried closing the choke a bit when the rough running starts?
If closing the choke helps the rough running then it is a lead pipe cinch that there is something amiss in the fuel system.

TRUE GRIT

[MN John]

I havent been back down to the boat yet to try the new portable tank with clean fuel.

I did grab a new deck fill o-ring too since I was at the store.

I havent really gave the tank much attention yet so I will still have to figure out how to remove pick up tube, get access for siphoning some out for inspection like u suggested, etc.

I dont think I ever messed with choke when having the issue, but I do think this is most likely a fuel issue.
My to-do list
1. run motor with new portable tank, and known clean fuel
2. replace deck fill o-ring
3. remove pick up tube and clean out.
4. remove some fuel from bottom of tank for inspection
5. check all fittings for air leaks

Anything I should add to the list?
Thank you for the advice and direction, I appreciate it.

[JOHN COOKSON]

.There is a kind of loud sound coming from carb when running, like if u were blowing into a straw and very quickly covered and uncovered the end. I thought this was the sound of debris in a jet, but I now think it is the scavenge tube picking up a bit of fuel in throat?
!

Maybe this is due to the air filter\back flame arrestor set up you have.
Try running with the air filter\ back flame arrestor open temporally and see if the noise goes away.

TRUE GRIT

[MN John]

Maybe this is due to the air filter\back flame arrestor set up you have.
Try running with the air filter\ back flame arrestor open temporally and see if the noise goes away.

TRUE GRIT

Ok, I will take a look at that as well.
someone did machine up a neat little adaptor plate for that air filter/back flame arrestor, so its the original housing. I might have the flame arrestor frame too, so I would only need the screen if it proves to be an issue.

[roadnsky]

I might have the flame arrestor frame too, so I would only need the screen if it proves to be an issue.

FYI if it comes to it, MMI sells the screen here.

[MN John]

back in boat

Ran motor as is for an hour, no problem. Next day added fuel, ran fine for 20 min, started dying bad. Hooked up new tank, ran bad for a couple minutes then running fine. 20 more minutes, dying bad, restart,die,restart, die. Choke just kills motor. Maybe it is ignition? Flame arrestor removed still makes sound mentioned earlier. I did talk to tom at indigo and my optical trigger has been grounding out, leaving a hole in top of optical trigger and bottom of rotor, but I replaced rotor and still a problem.
see pic in ignition issue post. So I ordered new parts from him. I have a temp gun and when I close up engine compartment, coil climbs to 200+ could this be it? Starting to bother me its beautiful out today and I am working on motor once again... By the way I am on a phone so its hard to type, hope I didn't leave any impor
tant info out. Any ideas? FYI running again no problems while I type, oh man... Also, a lot of condensation at intake, temp is 50degrees at the carb intake connection, another possible area of water contamination?

[Dave Neptune]

Condensation on the "outside" of the intake just above the butterfly area can be normal. Once the box and/or the carb warm up the condensation should disappear. What is the humidity? If hi and the condensate was outside I would not worry. The expansion of air and fuel in the venturi will chill the air mass.

You may have a suspect coil. Have you "ever" left the key of while working on the beastie?

Dave Neptune

[MN John]

Thanks for clearing up the condensation concern, yes its humid. Recently started reading rule 2011 related posts, and although pretty much mind boggling to me, it is why I thought to check coil temp and ordered resistor. It is a new MMI coil and I could swear it had this issue a few times before I replaced it, but its been awhile so not 100% on that. No key, I have a pull out ignition knob and push button starter. Definitely have left ignition on when jumping OPSS and probably other times as well. I always have battery switch on listening to radio when working on motor.

[ndutton]

Definitely have left ignition on when jumping OPSS and probably other times as well.

This coil can no longer be trusted. The sooner it's replaced, the better. Along with the new coil I recommend installing at least the basic alarm system (oil pressure and engine temp) to alert you when the ignition is left on and the engine is not running which spells death to a coil.

If you find the alarm buzzer annoying, good. It's supposed to be.

[Dave Neptune]

John, you may want to check the pull switch for integrity. Key-switches and most any switch exposed to a marine environment can be suspect too.

It does not take long to fry a coil if left on.

Dave Neptune

[MN John]

I will order new coil, and will look into the alarm systems. I had to have ignition on to jump opss to flush main plug with electric fuel pump, how do I do this with ignition off? I ordered a resistor from indigo, is that with a new MMI coil a good set up? I had no idea about ignition on/ coil damage, I will be very aware of this now. I did check the wires were secure on ignition switch, but I will replace. Any reason I should not replace with same style? Thanks for the advice, I appreciate it