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2004 5.0 litre Electrical Issues

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BurntGreene

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Hi, I am looking for some help in diagnosing a problem with my inboard. I have had the boat for 3 seasons, and we live in a 4 season climate so we do winterize our boat and store it at the marina that we rent a slip from. They also happen to be certified Mercury mechanics. The first year we owned the boat, it ran great and was super reliable..... no issues. The second year, the boat started to pop, sputter and loose power after about 45 minutes of use. I could bring the boat down to an idle and make it back to the marina most times but I did have to be towed once and it sucked. The marina mechanic would test drive the boat and not be able to recreate the issue, so we started replacing parts that "could be responsible" for the boat acting like it did. Each time we replaced a part, I would take the boat back out and the engine would start popping and sputtering again. The marina could never recreate the issue, I suspect because he would not drive the boat long enough or not get the engine hot enough. Eventually the boat did act up while he was in the boat with me. Here is a list of what was replaced before the mechanic heard the problem: 1. Rebuild the carb 2. new distributor cap and rotor 3. new plugs After the mechanic heard the issue, he felt that the engine was making the sound from the back of the engine and suggested this part: 4. new distributor module under the distrubutor (I think it affects the timing) I need help..... any feedback would be appreciated.
 
It sounds like the "certified mercury mechanics" may not be so certified.
Zero trouble shooting and only swapping parts....thats number 1.

Based on your entire ignition system has been replaced and a carb rebuild.

I would say you have a fuel related issue.

Possibly, something floating in gas tank and eventually clogging pick up tube,
Maybe a gas tank vent issue causing vent to clog and creating a vacuum causing loss of fuel flow.
Maybe the anti-syphon valve is sticking closed after a while of running.

Any chance of water in fuel?
Have you removed water separation filter, dumped contents into a glass jar and analysed for crap/water?

Being its a 2004, carbed, you have an electric fuel pump, has it been confirmed or tested to see if you are getting fuel to carb at at least 4 psi when your issue occurs?

Fyi, based on all the parts that those "Certified" people have thrown at your boat, I would imagin that they should now try to resolve the issue once and for all for free seeing as nothing they have done and charged you for has resolved your issue or at least insist on a refund for all parts and labor unil they resove your issue.(just my opinion)
 
OK fire Jim the ding dong at your marina. Fuel starvation does not mean replace the distributor module. While I would be mad as a wet cat, I wouldn't let those fools put their grubby paws on my boat for all the tea in China. It's time for you to roll up your sleeves and start fending for yourself. The first thing to do is to replace the water separating fuel filter. I am willing to bet that you don't know when it was last replaced. Not good. You should be logging any and all maintenance somewhere, even if it's writing the replace date on the filter with a sharpie.
The next thing to check is the fuel tank vent. In my area, it's a place that mud wasps love to build nests in especially if the little screen has fallen out. If the tank isn't vented it will build up a vacuum and the fuel won't draw.
If both the filter and the vent check out, then you move on to things like a fouled pickup tube in the tank. This you can detect by blowing into the hose that goes to the pickup and detecting good flow. You want to be able to blow air bubbles into the tank without any restriction. If that checks out you move on to the fuel lift pump.
The fuel lift pump could be either electrical or mechanical. Dunno which one you have. In either case the pump should be producing a certain flow and pressure which can be measured. We can help you figure that out if the previous steps don't relieve the issue.
The carb has been "rebuilt". A scary word in the boating world. I find that unless this has been done by an expert shop it can open up a whole lot of possible issues from the floats being out of adjustment to, well, a lot of things. Nothing beats a new carb and an Edelbrock 1409 marine unit can save you a lot of **** coming from the spouse. Is $500 too much to spend to keep him/her smiling? I know the answer to that for me.
Anyway, do those things and get back to us.
 
Thanks and I will work on these things. The boat does seem to run great, then it doesn't. When it happens, the engine seems to be very lean. You are right, I don't know when the water seperating fuel filter was changed. Not by me so I should look into that. Thanks to you both for taking the time to help me out.
 
The vast majority of I/O equipped boat have anti-syphon valves at the fuel tank...so the pickup tube test suggested in post#3 won't work.

Troubleshooting will always be faster than part changes guesses for finding the real problem...and likely cheaper as well.
 
Depends on where the anti-siphon valve is located. If it's at the top of the pickup, then yes one would have to work around that. Assuming it is the ball and spring type, you can actually blow a little bit through it without it shutting off. Maybe you have a tank that allows the pickup to be removed. That assumes of course that the manufacturer didn't bury the tank under the floor and foam it in place so you can't get to it
 
So I did another bay test and ran the engine until the skipping started again, which took about 40 minutes. I took off the gas cap, located on the upper starboard side of the boat, thinking that if the venting tube is clogged, the introduction of oxygen back into the gas tank could help with the issue. the boat still would idle (thank God) but when I tried to throttle the boat and give any more gas to the engine, it would cut out. The water seperator/ fuel filter was changed... The next thing that was suggested by the marina was to recreate the problem, then change over to a different fuel tank (portable) and run the boat to see if that changes anything. The first 40 minutes of running the boat is always great. Frustrating
 
You could just plumb a vacuum gauge into the suction side of the fuel system...there are typically 'extra' pipe fittings on the filter head...

Either way, just be mindful of any disconnected fuel connections - you only get one chance with vapors...
 
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