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Fuel issues? need advice- Pics inside

Old 03-19-2011, 09:57 AM
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Default Fuel issues? need advice- Pics inside

I'm trying to diagnose an issue my my motor and need some input.

I bought a used boat a few weeks ago and it came with a full tank of gas. Now I have no idea how long the boat sat before I purchased it, but when I talked to the previous owner he said he kept stabil and the correct 5:1 oil mixture in the tank at all times. He also said the motor ran great the last time he used it, but that was at least a year ago.

I ran into some hard to start issues and ran a sea foam treatment using new gas in a separate gas can and it ran great from the dock yesterday, but as the day went on it got progressively worse to the point where we had to limp home on half power not even able to get on a plane.
My buddy and I are almost positive it's the carbs and I am in the process of cleaning those, BUT it's not going to do any good if the fuel in the tank is contaminated. Since I do not have any way to drain and purge the tank myself I am going to have to find some place to drain the tank and clean it for me.

Could you guys look at these photos and tell me if this looks normal? I work as an Aviation mechanic and I am familiar with aviation fuels, but marine fuel treatments do wierd things to fuel and I have never seen fuel this dark (except when there is something wrong with it like algae or microbial growth of some kind.

Let me know what you think. I place some fresh gas without any additives from my lawnmower next to the boat fuel just as a contrast.
The dark green on left is boat fuel and clear on right is straight gas. The fuel sample was taken at the entrance to the motor after the fuel/water filter.





In this shot I did not see any particles or water collecting, but the dark green haze bothers me.
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Old 03-19-2011, 10:08 AM
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Originally Posted by Seawolf_504 View Post
I talked to the previous owner he said he kept stabil and the correct 5:1 oil mixture in the tank at all times.
The green tint is either the oil or the stabil. 5:1 oil mix seems extremely high though, most 2 stroke motors run on 24:1 or 32:1.
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Old 03-19-2011, 10:30 AM
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Originally Posted by UBETRUN View Post
The green tint is either the oil or the stabil. 5:1 oil mix seems extremely high though, most 2 stroke motors run on 24:1 or 32:1.
Maybe he meant 50:1, that would be a lot more normal. 5:1 would involve gallons of oil, must be a typo.
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Old 03-19-2011, 10:33 AM
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Does your wife know your using her good measuring cup and bowl for gas?LOL
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Old 03-19-2011, 10:34 AM
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Well I just swapped out the fuel/water filter before we went out this last time and ran sea foam through it with a separate tank of fresh fuel and it ran pretty well for the first hour yesterday, but like I said progressively got worse as the day went on.

The only thing I can think of is the fuel.

Let me throw this out there. Once you pump the primer bulb until it's stiff should it stay stiff while you are running the motor or does it lose pressure as the engine draws fuel?
Whenever I had a hard time getting it started I would pump up the bulb until it was stiff again and the motor would crank.
Maybe I have a leak in the fuel line somewhere? Air being sucked in?
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Old 03-19-2011, 10:35 AM
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Originally Posted by haikumaui View Post
Maybe he meant 50:1, that would be a lot more normal. 5:1 would involve gallons of oil, must be a typo.
Sorry yes 50:1
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Old 03-19-2011, 10:36 AM
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Originally Posted by fishingfun View Post
Does your wife know your using her good measuring cup and bowl for gas?LOL
Luckily she doesn't visit this site. lol It's an old one anyway.
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Old 03-19-2011, 10:39 AM
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I would change the filter in the water seperator and if it does not have one add one. When it satrts to run rough take the filter off and dump it out. Keep doing this until it clears up. Then replace the filter. You can also by a filter with a drain bowl on the bottom and when its running rough just drain the filter. Thats the type of filter I had and it took 2 tanks of gas to resolve the problem.
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Old 03-19-2011, 10:45 AM
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You don't say what motor. Please share. If there's a "see-thru" engine mounted fuel filter, it might be worthwhile to run the engine with the cowling off and watch the fuel filter bowl to see if it is "starving out" or shows evidence of air being introduced into the fuel system.
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Old 03-19-2011, 10:47 AM
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Originally Posted by fishingfun View Post
Does your wife know your using her good measuring cup and bowl for gas?LOL
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Old 03-19-2011, 11:11 AM
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It's possible the green tint near the bottom is at least partially due to other colors being filtered out in the upper layers of the 50:1 mix, Just as green is is the last to be filtered out as water depth increases, plus the oil is greenish blue to begin with. The pic doesn't show any obvious sign of phase separation, but it doesn't mean the year old fuel is still as peppy as it was when filled or has the same octane rating.

I'd 1st check the plugs to see if they are fouling , & dump the contents of all filters and carb bowls through clean rags or layers of paper towels to see if there is sign of gomph before emptying the tank . Was the tank stored full and is still nearly full? If the tank is say 1/2 empty a fill with new gas and appropriate oil could get you running better , and the next tank even better. But I'd fill w/ 1 octane level higher in the 1st fill.

If you temporarily run on a separate portable tank of new 50:1 mix fuel and it runs better again underway you will know the carbs are OK.

The primer bulb isn't getting sucked flat is it?
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Old 03-19-2011, 11:33 AM
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It looks to me like there is an awfull lot of 2-stroke oil in that fuel.
Stabil at a rate of 1 oz/10 gal is not enough to change the color of the fuel to green. Neither is the 2-stroke oil at a rate of 50:1. You got a heck of a lot of oil in that fuel to make the fuel look green and certainly enough to start clogging the engine fuel disrtibution system that E-10 has the ability to clean
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Old 03-19-2011, 11:40 AM
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I'd check the fuel pickup screen, anti siphon valve and make sure the tank vent is breathing correctly. You might also have a kink or otherwise restricted flow of gas between the tank and bulb?
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Old 03-19-2011, 11:41 AM
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I agree that it looks awfully oil rich, however it's tough to tell from a picture. How confident are you that you have the propper mixture? If you are too rich you could be loosing cylinders as the plugs foul.
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Old 03-19-2011, 11:50 AM
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first I would remove carb drain screws and see what the end of screw looks like, clean or varnish if clean go to 6 gallon tank and retest if varnish drain tank change filters and clean carbs again and retest. what engine
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Old 03-19-2011, 01:06 PM
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Sorry guys it's a 1998 Mercury Force 90hp 2 stroke. It's a 3 cylinder with one carb per cylinder. I pulled the plugs as soon as I got back home yesterday and they had a little bit of loose carbon on them, but they wiped off really easily. I'll be replacing the plugs too since they are cheap.

My Dad seems to think maybe the inline fuel filter inside the cowling might be clogged since the engine idles fine but has issues on the high end. Maybe once the engine starts to really draw fuel it can't get what it needs through that filter.

I think what I will do before taking the carbs apart is start where the fuel enters the carbs and work my way back to the tank replacing everything and starting fresh. This way I wont be doing carb work twice. Looking at the fuel in the sunlight I don't see any water or debris suspended or settling in it so I think the fuel is ok.
Once I get the carbs cleaned I think I'll fill it up with some high test (its at about a half tank now) and mix accordingly. Maybe the half tank of high test will help energize the older fuel.

Thanks for all the suggestions fellas. I'll keep you informed.
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Old 03-19-2011, 01:08 PM
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I would drain the carbs, check the plugs, and change out the filters. Then get a fuel pump and drain the tank--replace with new fuel, and 50 to 1 oil ratio. It is possible that you have a bad anti siphon valve, or clogged vent if the bulb goes completely flat. I would check both of those out also. The old fuel can be diluted and run in a yard tractor etc.
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Old 03-19-2011, 01:28 PM
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does the bulb go FLAT, like sucke in, or just not firm anymore? When you pump it it gets real firm, and that's correct. Once you start running the boat, it will lose it's FIRM ness, however it should only require a pump or two to get back to FIRM. Basically it will not be firm any more, but it should not have any kind of negative suction on it. It should also feel KINDA firm, meaning there is all liquid in there. If the first pump or two don't move liquid(if its quiet you can hear it), then i would say you have an air leak somewhere in the hose. Since you have the carbs out and apart, I'd clean them up, and just as you say, work your way back from the motor. I MAY reccomend getting a 6 gallon portable, and new hoses, and try working off that.

The color doesn't particularly disturb me, as when you use a dark(blue or green) 2-stroke oil, it does change the color significantly. What does however concern me is that it seems a little "cloudy" for lack of a better term. Think of it as beer. Even with oil, colorings, etc, gasoline should look like a plain coors light or miller lite. Yellow, but very clear all the way through. If it looks like blue moon, or some other unfiltered wheat beer, where you can't see through it, then you have bad gas. Bad gas tends to cloud up on you if it has sat for a long time. With the picture it is very hard to tell.
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Old 03-19-2011, 04:28 PM
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The bulb DOES NOT go flat, it's just not stiff anymore. It retains it's shape.

I just ran some more sea foam through the motor and it ran just fine even with the sea foam. Ran it for about 10 minutes then shut it down and let it sit for another 10 then hooked it up to the boat tank and ran it until it stopped smoking and disconnected the fuel line letting the motor run itself out of fuel.

It cranks right up and idles just fine, but yesterday it idled ok as well. It wasn't until we tried to go wide open that we had problems.
I'm going to go ahead next weekend and replace the fuel/water separator to a larger one (it's got a small one on there right now), replace the inline fuel filter running to the carbs inside the motor, and replace the plugs.

I've pumped out a few fuel samples from the tank and have yet to see any water collect at the bottom or debris so my gut tells me the fuel is ok or at least usable.
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Old 03-19-2011, 05:01 PM
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If you have a sample, for a fraction of anything you are going to spend "trying" things out to find a cause, just send the fuel sample out to a testing facility. You can contact one of the testing facilities, tell them what you have(a 50:1 mixture for an outboard motor), and ask them to send a container for you to put the gas in, and then send it back to them. Not sure about shipping procedures, but they can help you.
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