84 Scarab

So I made the mistake of not using my boat for 2 weekends in a row and now I am paying the price. When I got to the ramp first thing it did was flood when trying to start it cold. I have never had a problem cold starting it but I thought wth it has been sitting for a while. It proceeds to run like crap at idle for at least 5 minutes before clearing up and was seemingly ok. I attributed this to possible fouling of the plugs from the startup folley. I take it out and it runs good so I continue on my scheduled trip which was about 25 miles running it at over 40 with no problems. After I tie up for about an hour, I restart it with no problems but when I try to get it on plane it misses and pops out of the exhaust. I swapped a spare coil I had on board but it made no difference. I finally get it up to plane and am heading back but cannot go over 40 without much popping out the exhaust. As time goes by it becomes worse and worse and by the time I get it to the trailer I can barely keep it on plane it is missing badly, but idles smoothly. After bringing it home I check everything over and can find nothing wrong, although now it will not restart, just pops out the exhaust once in a while. Fuel filter is clean doesnt appear to have water in it, and the engine makes a nice blue spark when cranking over but no starting. I can see puddles of fuel in the bottom of the intake, so I take the qjet off and disassemble it to find no obvious faults. I should add that I dont know dick about a qjet lol I was just hoping to get lucky. Has anybody dealt with a problem like this before or have any ideas? I guess it would help to tell you its an 84 mercruiser 260 hp 5.7 that was converted to electronic ignition.

Scabby Jack

Did you try fresh gas?

84 Scarab

No I havent, but the gas in it was only about 2 weeks old and I had used it some on that tankful.

Of course thats not to say that after sitting maybe the water went to the bottom of the tank?

f_inscreenname

We got a lot of rain the last couple days. Nothing was left open was it? You may want to pull the plugs and see if anything is wrong.

tommymonza

Sounds like bad gas. I wrote about my experience with bad gas a month ago on a gas thread.This crap these days can be so bad that a lawnmower won't fire on it.

Pump out the gas and put some nice new in it and try it 1st before anything.

tommymonza

I put some old gas in my old truck just to try to burn it off.The truck would barely run. This was not gas that had water in it it just did not have enough octane to run a engine. So i had put 5 gallons of high octane on top of 5 gallons of year old fuel. Still would barely run with out spitting. So a quart of Seafoam Octane booster..

Truck ran much better but every time you parked the fuel would seperate and the truck would run like your boat until it mixed up again.

Our fuel is crap these days dont rule out bad fuel.

dereknkathy

do a compresssion test...

84 Scarab

OK IM going to pull all the plugs and inspect tonight, I have a comprassion tester so I will do that while the plugs are out also. I will report back any findings thanks guys. I'm hoping it aint bad gas because if it is there is alot in there and I dont know how I could drain it all.

4bus

Draining gas is easy, unhook the main fuel line and run an extension out of the boat, hit the vent with compressed air to get it flowing and it will siphon itself out. If it is bad gas it may run in a car which has advanced electronics to retard the timing and help run on low octane fuel.

One thing you have to be aware of is today's gas has ethanol in it and absorbs water easily, the marine environment makes it worse. Add that to the fact that base ethanol is so high octane they are adding it to lesser refined fuel to get the octane rating needed. When it breaks down you are left with 80 octane fuel with water in it

I try to keep my rotation of fuel at 2 weeks, burning it down to near empty

fleg1

I had a 454 mag that acted like that.. ended up having some bent push rods...