Mercruiser dies when throttle advanced

[ildoc]

I have a 1996 Mercruiser 5.7 Alpha one. Just got the boat out of storage yesterday.

Engine started fine (on the first try) and seemed to idle pretty smoothly. However, when I shifted into forward and advanced the throttle, it died. It restarted easily, but the same thing happened when I shifted into gear and tried to accelerate. Even advancing the throttle slowly didn't help.

This happened 4 or 5 times, then I decided to let it idle and warm up. After the temp gauge had moved up a little, I was able to shift into forward and accelerate up onto plane. The engine did hesitate a little as the throttle moved forward, then "kicked in" and seemed to run fine.

Throughout the afternoon, though, I had to give it gas slowly at first to keep it from dying.

Engine got new plugs this spring. Any thoughts/suggestions?

 

[Don S]

Re: Mercruiser dies when throttle advanced

Sounds like the carb accelerator pump might not be working. Pull the flame arrestor off, and with the engine off, disconnect the throttle cable. Then operate the carb linkage and see if you get gas squirting out of the jets.

 

[ildoc]

Re: Mercruiser dies when throttle advanced

How much gas should I see. And what should I do if I don't see any?

I live about 140 miles from the lake where the boat is, so I like to go prepared to make repairs, if needed. (This may be beyond my skill level, as well.)

 

[Haut Medoc]

Re: Mercruiser dies when throttle advanced

How much gas should I see. And what should I do if I don't see any?

I live about 140 miles from the lake where the boat is, so I like to go prepared to make repairs, if needed. (This may be beyond my skill level, as well.)

Two good streams......
If you do not see any, you need a rebuild, at least the accelerator pump, anyway......​

 

[claycts]

Re: Mercruiser dies when throttle advanced

How much gas should I see. And what should I do if I don't see any?

I live about 140 miles from the lake where the boat is, so I like to go prepared to make repairs, if needed. (This may be beyond my skill level, as well.)

I assume yoou have the stock 4 barrel. Look in the front 2 barrels those are the primary you should see a strem of gas coming out of 2 nozzels, one in each bore. It is a real strem not a drip.
I went through the same gas game onmine. The fix was!
New fuel/water seperator filter (spin on) about $12.00. Pull the fuel feed at the carb and clean the filters in the carb. It is a 3/4" barss fitting with the strainer in the inlet. Cost, $2.95 can of carb Cleaner. While you have the flame arrestor off, wash out the bores in the carb with the carb cleaner. Open the botterflys and let the clean just go in the engine, no harm.

Put everything back together, get fire bottle and have ready in case you did not tighten the fuel connections orthe filter. Also a drop of oil on all the linkages and the choke flapper shaft will also help.

Take Care
George P.

 

[Coors]

Re: Mercruiser dies when throttle advanced

Replace the brass-looking filter in the carb; basically un-cleanable, as it filters the last fine particles that try to enter the carb.

 

[ildoc]

Re: Mercruiser dies when throttle advanced

Thanks for all the tips, guys!

How hard is the carb filter to get to and how hard is it to replace?

 

[Don S]

Re: Mercruiser dies when throttle advanced

How hard is the carb filter to get to and how hard is it to replace?

It's not hard, just remove the line and then unscrew the holder. But I doubt that filter will be causing any of your problems. If it was plugged up enough to not allow gas to the accelerator pump, it sure wouldn't run on plane, and probably not at idle either. The 96 engines had water seperating fuel filters on the engine that would pick up smaller stuff than the screen in the carb filter.
Did you check the water seperating fuel filter for water? When was the last time it was changed?
Also, what carb do you have on your engine, 2bbl Mercarb, or 4bbl Weber?

 

[Coors]

Re: Mercruiser dies when throttle advanced

Don, the separator is finer than the little filter in the carb? Learned something new here.

 

[Don S]

Re: Mercruiser dies when throttle advanced

Don, the separator is finer than the little filter in the carb?

Absolutly. All the filters in the carbs are the nylon mesh anymore. Not the pleated paper.

 

[ildoc]

Re: Mercruiser dies when throttle advanced

Thanks again, Don.

But, what do I do if I don't see fuel squirting out of the jets? Do I have to have a carb rebuild?

What if I DO see fuel squirting.....where do I go next?

Sorry about the "what ifs." I just don't want to drive 140 miles with only one thing to check.

And is there a place where I can see a photo or diagram of what I'm looking for before I get there?

Filter/separator was replaced at the end of last season. Don't know which carb......will have to check