? about carburator and excessive fuel consumption.

[Salmon Stalker]

I got my boat out this weekend for the first time this year. Before I took it out I found that I had fuel problems (crap in the tank) that I worked out prior to heading out on this trip. Well, mostly. I now have a problem of a different kind. I went from blockage in the line so I didn't get fuel to the carburator. Well, when I went out I ran out 3 miles, trolled for 3 hours and came back 3 miles. This used 10 gallons of fuel in my chev 250. I was also smelling gas for a while and kept running the blower to keep the fumes out. I did not find any leaks in the line, but there is no way that that engine should be sucking down that much fuel.

When I got home I ran the engine to flush and it seemed I had unburned gas coming right out the exhaust. There is a slick spot on the driveways where the exhaust was coming out and hitting the driveway. I'm not sure what would cause that, unless it's fuel/air mixture too rich. My other thought was the timing could be off (I don't have any readable marks on my timing cover). But it ran good and wouldn't have thought timing to be the problem.


Any help would be appreciated so that I can finally be done getting things most of the way fixed.

SS

[Salmon Stalker]

Come on guys, I really need some help here. I think it's got to be just an adjustment somewhere. I can't go fishing and keep dumping gas out of my exhaust.

[Herring Problem]

Have you checked all of the fuel lines for crakes? Then check the timing and plug wirs.
You may have a carb with a blown power valve, or it may be time to have the carb rebuilt and cleaned.
Seen this on several customer boats over the years.
Good Luck Dennis :dance:

[Woody]

What is your normal fuel consumption rate? What hull?

I'm assuming this chev 250 is a 165hp Mercruiser. Or maybe it's a 250hp in which case it's a Chev. 350CI (I think). In any case, first thing I would do is properly adjust the carb and tune the engine (plug, points, cap, rotor, and maybe the wires)You can do it all yourself with a Clymer manual. Powell's on-line has them.

[Salmon Stalker]

I should have given a little more info. Yes it is a merc 165 hp. It's a deep-v 1974 sabrecraft. I can't tell you what my exact fuel consumption normally is, but usually I can make the same run and be gone all day (7-8 hours) on the same amount of gas.

As for what I've allready done. Motor has been replaced two years ago. Carb was professionally rebuilt last year. All three fuel filters (water seperator, fuel pump filter, and carb filter). I have timed it, but am unable to read anything on the timing gauge so I could easily be off by 2 degrees, but it ran so good at high speed it didn't seem likely. Newer plugs, wires, cap and rotor. Also just replaced the points 2 days before I took it out.
I also just checked all fuel connections and couldn't find any leaks in that or the line.

What do you think? Thank you for your thoughts already. http://www.ifish.net/gallery/data/500/4591boatsigns.jpg

[lingslayer]

It sounds like some of the "crap" that was in the line came loose (before you cleaned the line) and got stuck in the needle and seat assy in the carb. When this happens the needle can't close fully on the seat and slow/shut the fuel flow off to the carb's float bowl.
A very rich mixture and high fuel consumption is the result. Pull the plugs and see if they are black and/or wet with fuel. If so, that is the proof of rich mixtures.

You may need to pull the carb apart again and clean the guck out. Replace the float if it is plastic.
Good luck,
Jamie