Mercruiser 4.3 Engine - empty carb bowl

[karlesvandenborn]

Hello all, I've been reading here for awhile and always find the answers to my problems (thanks for providing the support). But, I can't seem to find the answer to my one big problem after doing lots of research.

Boat: 97 SeaRay 4.3L 175

Problem: Last two years its been hard to cold start after sitting for 1+ days. This years has progressed to be even harder to start. The only way I can seem to get it to start is by using starting fluid or pouring gas down the carb. Once it starts and finally achieves idle, the boat will run like a champ all day. But, starting it can be a 15-20 min process.

Research:
1. Check the oil pressure switch - if the oil pressure switch was faulty, wouldn't it not allow the engine to run at all? (bc the fuel pump is not being fed the voltage to run). The boat runs fine, once manually feeding the engine with gas.

2. Changed out the fuel filter - still no solution. The fuel filter did hold gas, so I know the fuel is not sneeking back into the fuel tank.

3. On the double barrell carb - Sometimes fuel squirks out and sometimes not (when priming from the throttle). The carb was replaced 3 years ago by a dealer. But idles and runs fine once the engine is going. I beleive the carb should be fine.

I am very fimilar working with engines. I've built a few competition skis and keep my other powered toys running correctly. But can not figure this problem out. So, any sugggestions or tips would be greatly appreciated.

Hello I am new to the forum. I am from the Netherlands so forgive me some textual issues… I have the same issue, empty carb bowl after 3 days. My idea is to mount a return valve in the fuel line, see attachment. What do the forum participants think of this? Thank you for your replies, Karles.

 

[Candy Gramformongo]

You probably already have a valve like that at the tank outlet to prevent siphoning. So adding another one is not likely not solve your problem.

 

[Bondo]

Hello I am new to the forum. I am from the Netherlands so forgive me some textual issues… I have the same issue, empty carb bowl after 3 days. My idea is to mount a return valve in the fuel line, see attachment. What do the forum participants think of this? Thank you for your replies, Karles.

Ayuh,....... Welcome Aboard,........ I'd sooner think, you have a leak in the carb float bowl, as gas can not flow uphill past the needle seat to get back to the tank,......
Rebuild yer carb, paying close attention to any welch plugs in the float bowl,.....

 

[Scott Danforth]

I'd the carb bowl is empty, you either have leaking welsh plugs or the carb sat for 3 weeks or more

 

[karlesvandenborn]

You probably already have a valve like that at the tank outlet to prevent siphoning. So adding another one is not likely not solve your problem.

Tanks, I indeed read somewhere that the standard valve is in- or close to the fuel pomp. This valve is already 25 years old, so maybe out of functionality (?). I thought that an extra valve in the fuel line will not do any harm.

 

[karlesvandenborn]

Ayuh,....... Welcome Aboard,........ I'd sooner think, you have a leak in the carb float bowl, as gas can not flow uphill past the needle seat to get back to the tank,......
Rebuild yer carb, paying close attention to any welch plugs in the float bowl,.....

Yes I will do this this spring thanks!

 

[cyclops222]

I could drain the carburetor bowel easily. Race back to the dock area getting the engine very HOT. Quick slow down and a quick docking. The engine was boiling off the gas in the carb and bilge smelled of gasoline.
I now am more intelligent about heat build up in cast iron engines. Thermostat was good and stayed at 160 F while zipping around.

 

[Bt Doctur]

dirt debris in the needle and seat, leaking float filling with gas and not able to shut the fuel off.

 

[Scott Danforth]

Tanks, I indeed read somewhere that the standard valve is in- or close to the fuel pomp. This valve is already 25 years old, so maybe out of functionality (?). I thought that an extra valve in the fuel line will not do any harm.

the valve is in the fitting at the top of the tank pickup. its a spring-loaded metal check valve. mine in the boat was over 38 years old when I last checked and working perfectly. that is well over 1500 hours of running thru that little check valve. other than dirt in the tank plugging them up, they generally do not fail.

since your carb is dry, the primary culprit will be the welsh plugs. however fuel will evaporate out of the carb over a period of 2-4 weeks depending on air temperature unless the engine is overheated, then that period of time reduces drastically

 

[rolmops]

The smart thing is removing the carburetor and do a complete rebuild or have it done. There should be places in the Netherlands where people do this. If you do anything less than the whole job,it will come back and bite you in the $$s. Also make sure to find out where the fuel smell comes from. I really don't like the idea of fuel boiling off next to ignition wires and spark plugs.

 

[rolmops]

By the way. If you have a problem with naming a part because you know the name in dutch, but not english. Have a look at my avatar. I can probably help you.

 

[karlesvandenborn]

By the way. If you have a problem with naming a part because you know the name in dutch, but not english. Have a look at my avatar. I can probably help you.

Bedankt Rolmops!