Finally made it out today....and had to be towed in

So we went to put our boat in late May and it wouldn't stay running. The boat had sat for 3 years with about 20 gallons of fuel in it. It ran fine on sea trial until I tried to cruise at low RPM and it wouldn't stay running. Talked to the surveyor and local marina and both thought it was fuel. They recommended topping it off with 93 octane and a bottle of Star Tron. Did that and it ran fine for the 10 hours or so we put on it last fall.
This spring started it on muffs and it was fine. Took it to the launch and it ran about 1 minute then died and wouldn't start. Brought it home and siphoned 20 gallons of fuel out (about 15 was bad the last 5 looked good) we had the boat out twice this spring and it ran fine. Went out today and putsied out of the no wake zone about 100 yards to the Ohio river then got up on plane. Ran about 1/2 mile up river on plane then came back down river about 1 mile then turned around and went to our anchor spot. When I backed off the throttle it stalled and wouldn't start. Dropped the anchor and pulled the fuel separator and dumped it in a container and it was about 50% bad fuel (separated). Had a new separator in the cabinet so put it on. After a couple hours on the hook we started it up and had to keep the RPM up for a few minutes to clear the bad fuel from the carb. After that I dropped it to idle and it sat there fine for about 5 minutes. Took off and got up on plane and all was good. Got the to entrance of our river and backed it down to about 1000 RPM's and it died again. Made it over to an old dock and tied up there and pulled the new separator and dumped it in a container. Fuel looked good. Put it back on and started it. It wouldn't start unless I pumped the throttle and would only run over about 2000 RPM. Anything under that and it stalled. We were only 50 yards from our slip so a dock neighbor came and towed us in.

So remember my boat is a 2006 Crownline but it has a 5.7 Merc 2 bbl with TKS. It has an electric fuel pump and you don't have to pump it before turning the key. It is NOT fuel injected

Any ideas? My first thought is more bad fuel but when I pulled that new separator after about 1/2 mile that fuel looked good. My thoughts are to siphon the remaining 45-50 gallons and put it in a 55 gallon drum for now then fill it with new fresh fuel and a new separator. If it still does it then I have 50 gallons of fuel to use as needed and look for a different issue?

My SR with twin 350 Mercs had three fuel filters. Each engine had a water separator, a high flow canister filter and a small nylon mesh filter in the fuel line just in front of the carburetor. If you have filters in addition to the water separator, they are probably clogged up from the bad fuel you have been running. In any event it seems like you need to keep cleaning up the fuel system. Glad we do not use e10 in West Michigan. My sympathies to you.

I cleaned that filter when I had trouble last time in late May. Not that it can't be clogged now but it seems to be fine over about 2000 RPM. We cruised on plane for about 30 minutes before we had this issue then after putting a new separator on it was fine for about 1/4 mile then did it again. But it would start and run good over about 2000 RPM. When I backed it down it would die.

If you have all the filters clean/replaced, it sounds more like a carb issue than a bad fuel issue. May want to play around with that a little bit before pumping fuel all over. Good luck.

If you are having repeat fuel contamination issues I would check the o-ring seal on my fuel filler cap.

Although startron is good, I would recommend Heat or Seafoam. Both are very good at removing water

hottoddie said:

If you are having repeat fuel contamination issues I would check the o-ring seal on my fuel filler cap.

Click to expand...

There is no o-ring. I will have to take a look tonight and get a pic but i looked into this and the filler neck has a rubber gasket that goes between it and the hull. maybe the o-ring is missing and thats my problem? i'll get a pic later and post it up

Just my two cents, you replaced the separater filter while out on the hook but didn't pull the other filter at the fuel pump? It too will hold all the same crap the separater was holding, some of the bad fuel will be in there as well as the bowl on the carb.

Could be water in the tank. If it only happened after coming on plane water moves to the fuel pick up in the tank and moves into the lines. Turbulence flowing through the lines keeps the water suspended until it settles out in the carb float blow.

A 1/4 inch of water on the bottom of a 60 gallon tank is a lot of water.
Drain the fuel tank COMPLETELY and then vacuum the bottom of the tank with appropriate equipment.

If you let the evactuated fuel set long enough and it is non-ethanol you may be able to recover the fuel.

A plugged filter is a fuel restriction. As a rule, it will allow low flow (good operation) at low rpm's and become a problem in the higher load/rpm range. Sounds like this is not what you are encountering.
Sounds like you have had water accumulation in your fuel tank but seems to be clear now?
Not sure what the humidity levels are in Pittsburgh, but topping your tank at the end of the day will minimize any contribution it may have.
It sounds like you have something else going on. I agree with Golfman25 as it being more of a fuel metering issue because it is in the lower rpm/load range. I would do a carb teardown or grab a new one if it's not in your comfort zone. Before doing so, confirm it is not something simple like your choke plate closing due an electrical issue. Had that trip me up once on an Edelbrock (Weber) carb. Same symptom.

So went to the boat tonight and checked a dock neighbors boat that is identical to mine. No o-ring on his fuel cap either. So siphoned 5 gallons out and it all looked like good fuel with no separation. Decided to try to start it and after 2 tries of sputtering it fired up and idled about 10 minutes until I shut it off. Waited about 10 minutes and tried again and it struggled to stay running. Pulled the filter at the carb and it looked good. Blew through it easily and put it back together. It started but didn't sound great. Took that filter completely out and started it again. It barely idled and stalled as soon as I gave it throttle.

No choke plate on this carb. It is a funky 2 bbl with TKS (turn key start). Has an electric fuel pump and you do not have to pump the throttle to start it.

Here is what mine looks like. It's a 2 bbl Mercarb
https://www.ebay.com/i/173872222303...1whg5SUUduTjl_d0w04yQSyf4j2zVP5BoCbikQAvD_BwE

So the link you posted (description) says that one is for an automotive application but does yours have that solenoid on it? looks like a fuel solenoid that GM used to use and your problems may be there if it got contaminated or is not working correctly. Maybe some GM guys will chime in.

Edit: It also says sensor testing and that is not a sensor, is there something on the other side?

Check your fuel vent. Maybe it's full of something????

Not familiar with that carb but sounds like techmich could be onto to something. Another thought could be to check the vacuum at idle below the throttle plates. Wouldn't think that would be temp sensitive but you never know? Have heard of problems with the 8 bolt intake manifolds leaking and you don't want to overlook the simple things.

That carb isn't identical to mine but very similar and pretty sure it does have the solenoid on the back. I'll have to get pics next time I'm down there. Not sure if I will go down today. The humidity is so bad the last few days that it sucks sitting in that engine bay.

Thinking of ordering a carb kit and replacing the separator again. This separator only has about 1/4 mile on it and when I dumped it it looked like good clean fuel

Not that it matters but the engine has 218 hours on it.

Oh, and turns out there is supposed to be an o-ring on that gas cap. It is just hard to see but mine does not have one so that will be fixed too but that isn't why it won't run right now so need to figure this out

I keep an o ring assortment from Harbor Freight on the boat fir on the spot repairs and replacements. Change them yearly and no issues.

ok. got weird today. Pulled the new separator and dumped it and all looked good. It would start and barely idle and die as soon as I touched the throttle. Looked down into the carb step-son said he could see water droplets laying on the floor under the carb. Sprayed a little starting fluid and it fired up but would quickly die. Bought another new separator on the way there so decided to put it on. Boat started right up and idled at the dock for 45 minutes until I shut it off. It started right back up and would take throttle without dying. All seemed good when we left. Didn't take it out as I was beat and storms were coming. But it seems the issue was a bad separator but it only had 1/4 mile on it?

If you have room for it I would suggest installing a Racor water separator filter with the fuel bowl at the bottom. They are easy to remove the drain plug to check for water in the guel and do a much better job filtering the fuel.

After reading up recently I thought about it but don't think there is enough room. I can barely get the regular one in there and not much room around there to put it. BTW I have been using the Sierra 18-7485 filters. Any issues with them?

You might have water in your float bowel as your low speed jets are in the bottom and as the boat moves around from the waves the water moves around in the float getting into your jets. Sometimes it starts and idles fine next time it doesn't as now the water is in the jets and the water is harder to get pulled thru the jets at low vaccum