hard starting and flooding

[jwjbs]

I have an 1984 century bowrider with a 260 hp (350) mercurycruiser. I have had problems with it hard starting with the engine is warm. I had the local marina put a carburetor kit in the rochester carb. It seemed to make it run better but it still would die every once in awhile while idling and then I'd have to give it throttle to get it to start. I posted a "hard starting when warm" thread on this forum and got several good recommendations. They included a new fuel pump, checking the float in the carb and adjusting the timing. I put in a new fuel pump because I had already had a carb kit put in and I thought I saw gas in the sight tube. Today....after putting in the fuel pump I gave the engine a try and I heard the engine backfire while I cranked to get gas to the carb. It then started right up and run good while I gave it throttle. I tried idle the engine down but it kept wanted to flood. I'd give it throttle and it would start running good and I'd throttle it back down again....once again it started to flood.

So I'm now starting to think of a couple things are going on. First it is getting more fuel with the new fuel pump but it is flooding. Maybe I need to adjust the carburetor jets? Maybe the timing is off since I heard it backfire? This is the first time I've ever heard it backfire. I had the boat in the yard the other day and it seemed to run pretty good out of the water. I just about did not put on the new fuel pump. Am I on the right track or is the carb float goofed up?

 

[Bondo]

Re: hard starting and flooding

I have an 1984 century bowrider with a 260 hp (350) mercurycruiser. I have had problems with it hard starting with the engine is warm. I had the local marina put a carburetor kit in the rochester carb. It seemed to make it run better but it still would die every once in awhile while idling and then I'd have to give it throttle to get it to start. I posted a "hard starting when warm" thread on this forum and got several good recommendations. They included a new fuel pump, checking the float in the carb and adjusting the timing. I put in a new fuel pump because I had already had a carb kit put in and I thought I saw gas in the sight tube. Today....after putting in the fuel pump I gave the engine a try and I heard the engine backfire while I cranked to get gas to the carb. It then started right up and run good while I gave it throttle. I tried idle the engine down but it kept wanted to flood. I'd give it throttle and it would start running good and I'd throttle it back down again....once again it started to flood.

So I'm now starting to think of a couple things are going on. First it is getting more fuel with the new fuel pump but it is flooding. Maybe I need to adjust the carburetor jets? Maybe the timing is off since I heard it backfire? This is the first time I've ever heard it backfire. I had the boat in the yard the other day and it seemed to run pretty good out of the water. I just about did not put on the new fuel pump. Am I on the right track or is the carb float goofed up?

Ayuh,.... What makes you think it's Floodin' out,..??

Have ya pulled the spark plugs, 'n seen their color,..??

 

[dmeals]

Re: hard starting and flooding

i have an 1984 century bowrider with a 260 hp (350) mercurycruiser. I have had problems with it hard starting with the engine is warm. I had the local marina put a carburetor kit in the rochester carb. It seemed to make it run better but it still would die every once in awhile while idling and then i'd have to give it throttle to get it to start. I posted a "hard starting when warm" thread on this forum and got several good recommendations. They included a new fuel pump, checking the float in the carb and adjusting the timing. I put in a new fuel pump because i had already had a carb kit put in and i thought i saw gas in the sight tube. Today....after putting in the fuel pump i gave the engine a try and i heard the engine backfire while i cranked to get gas to the carb. It then started right up and run good while i gave it throttle. I tried idle the engine down but it kept wanted to flood. I'd give it throttle and it would start running good and i'd throttle it back down again....once again it started to flood.

So i'm now starting to think of a couple things are going on. First it is getting more fuel with the new fuel pump but it is flooding. Maybe i need to adjust the carburetor jets? Maybe the timing is off since i heard it backfire? This is the first time i've ever heard it backfire. I had the boat in the yard the other day and it seemed to run pretty good out of the water. I just about did not put on the new fuel pump. Am i on the right track or is the carb float goofed up?

chk the plugs. If black sooted then warm engine & chk the choke to make sure it is fully opened.

 

[series60]

Re: hard starting and flooding

If that Rochester is original then the welch plugs may be leaking fuel into the manifold. That's a 28 year old carb! Google 'quadrajet welch plugs' .

 

[havoc_squad]

Re: hard starting and flooding

First, make sure you test fuel pressure on the fuel pump to the carb while engine running before investigating any further.

I made the mistake of trusting my "FORMER" service shop was competent enough to investigate a flooding issue.

Make sure the choke is fully opened when it is fully warmed up.

Then check the venturies that they are not dripping during idle or at engine off.

Fuel PSI should be 5 to 7 psi MAX to the carb at idle to about 1800 rpms.

Next, have the idle mixture screws been reset to service manual recommendations for adjustment on the carb?

Then from there you can try to adjust in the water, at idle and in gear the idle mixture screws to get the maximum smoothness in idle.

Follow the service manual procedure for adjusting the carb's idle mixture screws.

If it is a carb related failure then the idle mixture screw adjustments won't do any good, and that will be evident when you adjust the idle mixture screws on the water.

How you can tell? When you're in gear at idle for over 1 to 2 minutes in the water with the engine fully warmed up, any highly rich (idles rough but keeps running), flooding, or highly lean fuel/air mixture will be evident.

 

[jwjbs]

Re: hard starting and flooding

whatever it is....it is intermittent. One day I'll adjust the idle mixture screws and it seems to help. The next day it will start flooding from the start. I'll tried to adjust the mixture screws and it didn't seem to help.
The choke is working.
I put in new plugs and new coil. The old plugs were blackish....but didn't look real bad.
Carter fuel pump came from marine store. I haven't checked the PSI of the pump because I don't have the tools.
Timing was off slightly. I adjusted it a bit but ti did not help.

Any ideas?? I googled welch plugs but never found a good website.. I'll keep looking.

 

[Don S]

Re: hard starting and flooding

I googled welch plugs but never found a good website.. I'll keep looking.

Try this instead. Click Here

 

[Fishermark]

Re: hard starting and flooding

Hey Don - that's a pretty cool app and link you have!