Have Boat Questions? Ask a Boat Repair Expert.
Hello. My name is Tan.
Have you tried running the engine on a different fuel source? When you have debris in the fuel tank it will act exactly as yours is acting. We need to eliminate the boat side fuel system from the engine to be sure we have good fuel supply. You have done everything on the engine but you have not eliminated the fuel source as the possible cause.
Can you run the engine on a different fuel source like a 5 gallon gas can? Connected directly to the water separator filter?
Ok Where did you have the other fuel tank connected? Did you happen to bypass the weater separator fuel filter in your testing?
We need to check voltage at the ignition coil when it starts to act up.
If we are loosing voltage it will do the same thing the other test is to check the fuel pressure at the throttle body fuel inlet port when engine starts to act up. We have to verify fuel pressure and ignition when engine acts up.
Have you noticed what the volt meter is reading when the engine starts to act up?
The voltage should be steady. Fluctuation of voltage will cause the computer to go haywire. We need to check all the connections at the alternator and the ECM. Loose or corroded connections can cause the issue. Also a loose or dirty connection on the alternator.
Have you load tested the battery? So the voltage at the ignition coil is still going up and down is that correct?
I hope you mean a hot wire to the coil.
Did you bypass the water separator fuel filter? You can have plenty of fuel pressure and still have fuel starvation.
When the engine bogs down does the voltage at the ignition coil drop?
Lets try this disconnect the main engine harness where the boat harness connects to the engine harness. Connect you volt meter to the positive side of the ignition coil. Then with a jumper wire run from the battery cable connection at the starter. Now jump start the engine. Watch the voltage on the volt meter does it still fluctuate. Leave the starter and the alternator connected. What we are doing is eliminating all other outside sources to the engine as possible voltage issues.
Have you run the boat connected this way?
Is this a new distributor?
Well Dave I am out of ideas. I will opt out maybe another expert has an idea.
Hi Dave, my name is ***** ***** I am another expert here.
Can you run the boat for me today for a quick test?
HEI distributors are not used in boats. Can you take a picture of your distributor so I can see what you actually have.
The "standard" GM HEI distributor is the one with the ignition coil that is in the distributor cap. Such as this one in this link (click the link for a picture) https://static.summitracing.com/global/images/prod/mediumlarge/pro-66945bkc_ml.jpg
Is that the distributor that's in the boat now?
Yeah that distro isn't going to work, not only isn't it going to work that is either adding to your problem or is the problem. HEI distributors advance their timing via vacuum. Without advancing timing the engine doesn't make power. Boat engines do not make vacuum, and there isn't a vacuum line hooked up to yours anyways.
What other ignition systems do you have at your dipsoal, because the HEI isn't going to work.
What I want you to do is get a piece of scrap wire, an stick alligator clips on each end. Clip one end to the igniton coil positive, clip the other to the positive battery terminal. This will ensure a solid 12V to the coil at all times. Let me know if it runs better or does the same thing.
What exactly are you measuring? With the jumper I'm place it would not jump up and down.
With the jumper in place the voltage should not be jumping up and down. Are you positive the voltage was jumping up and down with the jumper in place?
It's a poor connection someplace, do you have a battery switch on the boat or do the cables connect directly to the battery?
If you hook the meter directly to the battery, does voltage fluctuate there or is it holding steady?
If your meter is fluctuating on the battery then you either have a bad battery or a bad meter. Go stick the meter on one of your car batteries, start it up, and bring the rpms up to 1500 or so and see if the meter voltage reading is fluctuating or not. That will tell you if the meter is junk or if the boats battery is junk, does that make sense.
Hi Dave, any progress?