20 Amp Blown Fuse (think it leads to fuel pump relay)

[nolalake]

I have 35' Chaparral with two 2006 I.B./O.B. MerCrusier 6.2 MPI engines. The problem started with my starboard engine stalling at slow speeds. However it would restart and run fine. My mechanic said it might be the Air Intake Valve that was not in stock and would have to order. Took the boat out and starboard engine died again but would not restart. Drove boat in on port engine and found a replacement Air Intake Valve at another dealer. Replaced part however boat did not start.

Mechanic said check fuses in same compartment mentioned above and middle 20 amp fuse was blown. Changed fuse and boat ran fine. (Note: Fuse had small blow and no black markings.) Ran boat for 3 hours straight no problems to first destination and stopped for the night. Started up fine and ran another hour. However we underestimated the fuel burned in first trip and ran out of gas. Once we were able to refuel bout ran fine for 20 minutes and starboard engine stopped. Checked middle fuse and it was blown with a 1/4 of the inside having black soot markings. Replaced the fuse again and turned the key but would not start. This time the inside of the fuse was completely blown. Took boat in and rented a slip.

After speaking to mechanics they said it might be the fuel pump. Purchased two new fuel pumps for the starboard engine and a fuel filter for each engine. After purchasing the pumps the mechanic said before changing the parts to change fuse, take power off of fuel pump, and start the key. This way if fuse does not blow then it is the pump that is bad. Did that and the element inside the fuse was completely gone.

Not sure if the Air Intake Valve or running out of gas had anything to do with the fuse blowing. Was hoping you could help because I am having a problem finding a mechanic in this small town. And the boat is an hour away so I wanted to be able to try a few different trouble shooting procedures when I return.

I will try what you mentioned above. In addition I read in this forum that it could be the fuel relay switch? Or is there a manual I could purchase to help with the troubleshooting?

Thanks for time and consideration.

 

[Don S]

Re: 20 Amp Blown Fuse (think it leads to fuel pump relay)

What's the serial number for your engine?

 

[nolalake]

Re: 20 Amp Blown Fuse (think it leads to fuel pump relay)

Thanks for the reply. Engine S/N - 0W353456

Last time at the boat I disconnected the fuel pump on the front starboard side of the engine. I spoke to another mechanic and he said that there is another fuel pump below the engine that I need to test the same way as mentioned above. If it is that fuel pump it is very difficult to replace. Said might have to take mounts off of engine to access pump.

Going to boat on Saturday to diagnose issue. If cannot fix dealer said he will have to get a trailer and move it to New Orleans for repair. Looking to avoid that cost if all possible.

Thanks again for your help and consideration.

 

[Don S]

Re: 20 Amp Blown Fuse (think it leads to fuel pump relay)

Both your low and high pressure pumps are in the cool fuel unit. There is no other pump under the engine. Unless they think you have the fuel cooler under the port front motor mount. In which case, they don't know what you have either.
Calling shops and asking for free troubleshooting information probably isn't going to get you much. They want your paid repair work for them to do.

Prime the cool fuel unit with clean gas. Hook up a remote fuel tank (outboard tanks work great) and see if it runs, or if the fuses blow.

 

[nolalake]

Re: 20 Amp Blown Fuse (think it leads to fuel pump relay)

Thank you very much for the reply. This is only my second season boating and I want to take advantage of every minute. It seems I was able to get a mechanic to come out Saturday morning. While waiting I was checking the wiring harness right after the fuse and it was slightly frayed. Put a piece of electrical tape over the spot, replaced fuse, and started engine. Once mechanic arrived he spliced the harness and insulated the wire to prevent corrosion. Said harness has been know to wear against engine at this spot.

He also changed the fuel filters which he said should be changed twice a year.

Thanks again for your time and have a great boating season.