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ibelieve

Prop slipping or engine missing during initial pull

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ibelieve

Almost feels like the prop/shaft is slipping on the hole shot and continues until 25ish mph and then seems to go away. I had this once before a year or two back and it just seemed to go away. The feeling is similar to a damaged or dinged prop but only up to 25 mph. It also greatly slows the hole shot. Guess it could be the engine missing but it feels like something is about to fall apart and makes me hesitant to continue to use it until I find the problem.



Wondering if anyone else has experienced a similar problem?



I just added 20 gal of gas. Always get the better stuff but buy it in 5 gal cans and it will sit in the garage, sometimes, for a couple of weeks before it gets used. It has been extremely damp and humid ... is it possible my problem is water in the fuel? I know for sure that I am now getting ethanol as I have problems with vapor lock that I never had before.



Any help is appreciated.



Thanks,



Steve


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REW

Bad gas is always a possibility, but only a couple weeks should not be a problem. Could also be a true missfire from an ignition issue, Lets rule out some easy things first. check plugs, cap, rotor, and fuel filter.

Have you checked your transmission fluid? Too low it will slip.

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tvano

trans slip will allow the engine to rev

engine rev-ing while experiencing the problem?

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Gord91f3

Have you seen any oil in your bilge, check to see if you have water in the tranny have an o ring on the shifter shaft of mine leaking can alwase tell by that slipping feeling that the fluid is low, but as soon as I'm on plane it runs fine also a lot of boats have a low speed miss. Check to make sure your plug wires are not shorting( if your gutsy just touch them when it's running ) if you live there ok.

Lotsa luck gord,

Ps have an old f3 so problems are the norm but I can fix them, the newer boats well let's just say bring another thousand when they don't run right

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ibelieve

Thanks so much for the good ideas. My first look was the tranny but the fluid is nice and red and full. I sucked it out and refilled it anyway with no change. Put some fuel system cleaner in and no luck there either. Was going to switch out the plugs with a spare set but must have pitched them. There is no fluid/oil in the bilge. I replace the fuel filter and removed the input fuel line from the pump and checked for blockage there as well.

It was interesting though that 2 runs after the fuel system cleaner, it ran fine and did so on the next pull. However, after a 30 min wait, it was back to doing the same thing.

I did pay more attention as we continued to use the boat. I am almost certain it is an engine thing ... like a mis-fire or timing advance ... as it takes off like a rocket when it gets up to speed. It is not always the same speed as when footing it sometimes doesn't rocket until 38 mph. Other times it will start to rocket at 28 mph. Once it gets over the hump, it is fine. It is just during the hole shot that it has the problem and the problem feels the same as an out of balance prop but sounds more like the engine is missing. It even sounds like it might be missing at ideal when in gear.

What might be an issue early and then start to work normal after reaching a speed or possibly a lessened load once the skier is up? I am wondering about timing advance? Is it a vacuum advance? I will check plug wires but not sure why it would not work well during the hole shot but be fine a few seconds later. Was going to replace the distributor and rotor (if it has a rotor).

Please, keep the ideas coming!

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Woodski

@ibelieve: you might try running the engine at night with the hatch open and see if you notice any arcing across the plugs or from the plug wires to anything metal, which would result in an intermittent miss. Your fuel cleaner test implies it might be dirty or clogged injector(s) showing issues at higher loads. Are all the fuel filters clean?

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ibelieve

I will give the after dark look a try next weekend, weather permitting. As for the filters, I saw nothing that implied a clog. Perhaps I am just a bit paranoid with the fact that I am now seeing ethanol in the fuel and the horror stories I have heard. I do put the Stabil for ethanol in for the off season months.

Seems to run just fine over 40 with footer in tow. I would think if there was any fuel system issues I would see some issue on the top end. It is like a switch is thrown when it goes from missing to rocket mode. Also, with it missing at idle when in gear, it shouldn't be consuming much fuel or seeing much of a load.

After doing some reading, it looks like timing is controlled by the ECM. Guess it might be one of the first things a dealer would replace. Perhaps if I put a timing light on it, I could watch for a sudden change when it goes from missing to rocket mode. Problem is, it would be easier to see after dark but my lake has no wake rule after 7PM.

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ibelieve

How about the knock sensor? Can I get a replacement from a local auto parts place or is it something special? It is a HH 380HP.

The sensor is rusted on the tip but I don't believe that should effect its operation. Is there an easy way to test it? Can I put a meter on it or a scope and look for a certain frequency output waveform?

Since I only see the boat on weekends, I like to be prepared with a number of things to look at or try.

I plan on looking at the plugs, checking the wires (after dark), ohm the coil, check the distributor cap, check the PCV valve (is this available from local auto parts?).

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ibelieve

I finally got around to doing something ... replaced dist cap, rotor, ad wires. Cap had some issues and the rotor had a piece broken out of the side of the mount, so I thought I might be on to something. The problem seemed to have subsided but not for long. Perhaps it was the weather as it was soon back to doing the same thing ... 0 - 27ish was like crap and then all of a sudden it would quit missing and I would pickup 3 mph.

In the meantime, I had fully emptied the tank and re-fueled with fresh 93 octane. I would have to drive another 60+ back road miles to fine some ethanol free stuff so that is not really an option. Anyway, being on fresh fuel rules out that as a possible issue.

Next I guess is to check plugs. Since this is multi-port fuel injection, does that mean it has one fuel injector per cylinder?

At the end of a couple of runs, if you lay on the engine cover you can definitely feel it missing, ad idle. It is not a regular miss but rather seems to be random in nature. The problem is definitely one of poor performance on the low end.

One other question, I can get access to the software to read the log from the ECM but am not sure what type of cable is needed? I seem to recall a note that it was available from Amazon?

Thanks for the help!

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ibelieve

Wow ... been reading this https://www.bakesonline.com/images/MediaLibrary/Indmar_MEFI4manual.pdf and finding a lot of good info. What is not clear to me is if a standard scan tool used on a car would provide readings from the Indmar ECM and if a standard ODBII cable would work or if Indmar uses something special?

It is also interesting that they describe an example of a sensor failure that is similar to the problem I am seeing ... rough running do to the ECM thinking the temp is cooler than it really is (and why it may run OK on the first pass and not once the engine warms up). Just a thought.

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oldjeep

No, a car scan tool will not work. You need an mefi scan tool.

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Woodski

@ibelieve: have you done a plug check and read them? Might give you a clue if random or not. I would also do a leak down / compression test. Have the injectors been cleaned & checked?

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ibelieve

The boat is on the water and I do not have easy access to a place to work on it where tools are available. I have to lug whatever I need to the boat. I will pull the plugs and see what they look like. I'm not sure what is meant by doing a plug check other than looking at them or just replacing them. As for compression, I have my doubts that it is an issue as the problem goes away at certain speeds. I can see an injector issue and they have not been cleaned, checked or removed.

I was hoping to hook a computer or scan tool to it to try and pin point a cylinder as I have a feeling it is just one causing the problem. Does anyone know what cable is needed and where to get it for use with computer based diagnostic software?

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Woodski

@ibelieve: when you do the plug check from a remote spot, bring the removal tools along with a magnifying glass and a good flashlight to get a good close look at the plugs. Look for an odd man out, particularly a wet one (no spark or too much fuel) or a dry one (no fuel). They should be a light tan color and of course all pretty much the same. There are some pretty good sites that have good pictures on what they should look like. As for the plug check, you really don't want to look at them after an extended idle as that can mask the problem you are looking for. Might help as a substitute for getting an ECU log or no codes when you connect.

Plug check - looking a the plugs after running the engine, usually done by running hard and shutting down to capture the plug condition in the critical operating phase (in racing at WOT and under load). Ideally, you would want to shut off and check as the problem manifests itself. Another option would be to get a thermal temperature gun (~$25) and shoot all the cylinders right at the exhaust port to see if they all read the same or close, a cold one would indicate a no fire condition (more challenging in a DD boat with water cooled manifolds, but you can get at the port from the underside of the exhaust manifold, and satisfy you contortionist needs at the same time).

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justgary

I don't think a MEFI tool is going to pinpoint a cylinder for you on MEFI4, but it can show you the basics like spark advance and injector pulse width. Using one is better than not using one, but I think you can continue down the troubleshooting path without one.

If you are handy, you can make your own tool to read MEFI.

You can also try a spark gap indicator that allows you to see the spark as it happens so you can find the dead one. I made one years ago with a board, a few screws and washers, and some old plug wires. Mine had four wires on it to test one side of the engine at a time. The gap can be around 1/4".

Yes, you have eight injectors.

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ibelieve

I built a tool to read the engine codes and a cable to use with TunerPro to read a little more. Did not get a chance to test either due to weather but did have time to replace my plugs and remove, clean and test all the injectors. My problem has either been fixed or was being effected by the 70 degree weather as the boat would usually run OK for the 1st set until it got warmed up. I may not know for sure until next summer but you can be sure I will report back here any future findings.

I may post a pic of my plugs to see if a trained eye can tell anything from them. Nothing seemed to jump out at me.

Thanks for all the help!

/Steve

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ibelieve

Here is a pic of the spark plugs. The arrow points to the front of the engine. When I cleaned the injectors, the one that is associated with plug #4 seemed to initially have a distorted spray pattern but I did not notice any issue with the rest. All of the injectors appeared to perform well when tested after a thorough cleaning.

20150929_185241a.jpg

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MadMan

FYI: Chevy cylinders are numbered in the order the rods are positioned on the crankshaft, front to back. This makes odds (1,3,5,7) on one side of the engine and evens on the other.

Ford numbers them 1-4 on one side of the engine, 5-8 on the other.

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ibelieve

Thanks. I just wanted to make sure I knew where each came from and which injector went with it.

FYI: Chevy cylinders are numbered in the order the rods are positioned on the crankshaft, front to back. This makes odds (1,3,5,7) on one side of the engine and evens on the other.

Ford numbers them 1-4 on one side of the engine, 5-8 on the other.

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ibelieve

I made a cable (see here for details - http://www.themalibucrew.com/forums/index.php?/topic/52012-lets-talk-mefi/page-2) and added a switch between pins A and B and an LED/resistor between pins E and F so I could use it as either a scan tool or connect the ECU to a computer running the appropriate software. An interesting thing happened when I closed the switch. Not only did the LED pulse out the codes but the buzzer/alarm (usually indicating no oil pressure with key on and no start) stopped its continuous alert and started beeping in sync with the LED. As such, at least on my 2004, the codes could be read by listening to the beeping without needing an LED.

As for connecting to a computer, I have yet to have a chance to try that.

The only code I was receiving was a 12, meaning there were no stored error codes.

Thanks to all the support ... you guys are great!

/Steve

This describes how to make your own MEFI scan tool for almost nothing:

http://www.pirate4x4.com/tech/billavista/MEFI/

If you want to buy the real thing, look here:

http://www.rinda.com/marine/marine.htm

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