Engine Troubles - 8.1 Horizons

M

mgranberg

New Member
Jul 16, 2008
4
Chicago
Boat Info
2003 340 Sundancer
Engines
8.1S Horizons
I'm having a problem with my port enging that seems to be evolving into a recurring and difficult to diagnose issue. I would appreciate any suggestions out there.

I have an '03 340 with 8.1 Horizons. About 260 hours.

The short story is this: We were having a problem losing the port engine. It would always restart, all systems normal. Sometimes, but not always, we also got a diagnostic alarm "Port Fuel Pump CKT." We have replaced both fuel filters and the fuel pump relay and are still getting the diagnostic alarm but have not lost power again...yet anyway.

For the long story...

While on our recent boat trip around Lake Michigan, we started losing the port engine periodically. The first time it occurred about 3.75 hrs. into our trip. Restarted (everything looked normal) and made it to our destination with no further problems.

The second time it occurred about 3 hrs. into the trip and recurred 3 times in the next half hour. We decided to leave it down and limped into our destination on the starboard engine. We also got a diagnostic alarm on the SmartCraft that read "Fuel Pump CKT."

Before going any further, we took it to the local Merc/Sea Ray dealer who hooked it up to the computer to no avail. We replaced both fuel filters and hoped for the best.

Had the same problem on the next leg but much sooner. About 1 hour in. Talked to Merc who suggested it was likely the fuel pump relay but couldn't be certain. Also indicated that it was probably not the fuel pump itself. Couldn't find anyone who could find the fuel pump relay much less have one in stock.:smt021

Started heading toward home hoping for the best. We made the next two legs without losing power but continuously got the same diagnostic alarm. The last 10 miles we lost the port engine 3 times with no alarm. We got it to the dealer where originally purchased who had no other suggestions and replaced the fuel pump relay. The return home, about 40 miles, we had no problem and though we were done. THEN, on a short cruise close to home, got the same diagnostic alarm though we still have not again lost power.

I apologize for the long winded description but thought the more info the better. I appreciate and look forward to any suggestions.
 
Can you hook up a fuel pressure gauge and observe what happens when the engine shuts down? What is the fuel pressure when the engine is running? Is it in spec? Check the wiring to the pump, the ground, etc. If you've replaced the fuel pump relay, replace it again and if it doesn't cure the problem, I would assume this isn't the culprit. If the wiring and relay check out, I would lean towards the fuel pump itself.

Doug
 
Friend had the same problem on his boat with the engine failing after a few hours of running, but his was a 2001. That was the first year for the 8.1s. The problem began from day one with the boat and continued until Mercruiser replaced all of the fuel pumps. I would have imagined that they finally resolved the problem by 2003, but maybe not.

First couple of years for anything new from Mercury are always experimental. They just don't test anything properly before they dump the stuff on customers.

Best regards,
Frank C
 
It may be your wire harness has a loose connection. The harness I am talking about is the one on the engine that connects it to the ecm and smartcraft. It is about 1 inch diameter and has about 12 wires inside it. The plug is a simple male/female type. My 340 would sometimes not restart after it was warmed up and we finally traced the problem to the loose harness connection. The tech from mercruiser said he had seen the same problem quite a few times before. That harness may be just loose enough to cause your problem.

Hope this helps.
 
Thanks all. I appreciate your thoughts. Going to give it another shot this weekend.

Regards,
Mike
 
How hot was it when all of this occurred? Mercruiser put a thing called "Cool Fuel" on some of their engines (not sure about the 8.1) to eliminate vapor lock. If the engine room is too hot, then vapor lock is another possibilty. I cannot find any info on the "Fuel Pump CKT" message.
 
i have a friend with a 2002 carver 396 who had a similar problem with one engine. he had crusaders, but the fix was replacing the wiring harness described above. apparently GM had a problem with the manufacturing process of these harnesses. the dealer took care of the problem on warranty. i'm not certain if the problem extended to mercruiser's 8.1s OR if it extended to model year 2003.
 
Thank you for the additional thoughts. Definitely going to check all of the wiring harnesses again. I did that initially but I've continued to have some issues with my analog instruments.

The engine temps were both in spec at all times. We did wonder if engine compartment temp had something to do with it though. We ran with the blowers the last couple days and didn't lose power until the last run on the hottest day. I don't know if outside air temp could really have any impact on engine compartment temp?

Regards,
Mike
 
Not necessarily the same, but yesteday, while traveling with a 2006 38DA with 420HP 8.1s, about an hour into our cruise, he radioed that his port motor shut down while on plane. Would not start....no power to motor. Coincidentaly we were about a mile from the local MM so we both pulled into the docks. Quick Plug...the MM in Brant Beach continues to be very accomodating and ready to help. They sent two mechcanics to the boat and found the main breaker had -popped-. Now....why? They did some basic diagnostic and took it for a test ride but couldn't find a reason. We pulled out and continued for another hour and a half without incidence. This was the first time this happened on this boat. We travel back in a few days and we shall see....
 
If relays and pumps are separate for each engine, I would start swapping parts to see if the problem moves to the other engine. If or when it does, you have found the faulty part.

Good luck!

Fred.
 
Just discovered this thread. Is anybody still active here? I have same problem.2002 sea Ray 380 8.1 horizons At About an hour and a half at cruising speed 3,200-3,400 port engine loses all rpm and sputters and won’t maintain speed. If I shut it down for 5-6 minutes it fires right up and runs fine. Have replaced the fuel pump and of course fuel filters and all the obvious things. I have been chasing this ghost for 3 years.
 
After it restarts is it good for the rest of the day or just another hour or so?
 
What I'm talking to is if it heats up and dies, then starts after cooling down, then fails again after an hour or so. It could be the ECM or ignition module over heating and failing intermittently. A simple test for this can be to have a cold bottle of water handy, if it dies cool the ECM and ignition modules thoroughly. If it restarts immediately then its an electronics issue.

What @scoflaw is talking about is even though you put a new fuel pump on these engines had problems with poor fuel pump relays and the relay socket/harness. They start to overheat and melt and the pins get loose.
Depending on your engine serial number Mercruiser had a service bulletin on that issue.
 
Off Mic said:
Just discovered this thread. Is anybody still active here? I have same problem.2002 sea Ray 380 8.1 horizons At About an hour and a half at cruising speed 3,200-3,400 port engine loses all rpm and sputters and won’t maintain speed. If I shut it down for 5-6 minutes it fires right up and runs fine. Have replaced the fuel pump and of course fuel filters and all the obvious things. I have been chasing this ghost for 3 years.
Click to expand...
Hello. I am wondering if you ever resolved your issue? I am having the exact same issue with my starboard engine for the past year. I have replaced the plugs, the spin on filter, polished the fuel, replaced the fuel pump and a number of sensors all to no avail. It seems as if it is getting worse as I was out fishing and at an idle speed for an hour when the rpm started to fluctuate and the engine died. It would restart but then died again after 10 minutes. It feels like a fuel issue but when running it with a gauge the pressure is fine and no alarms come up. Starboard is a 2001 8.1 merc. Is there abother fuel filter or screen that I am missing? The dealer tells me there is an inline but my mechanic and I can not find it anywhere. Any help would be appreciated. Thanks
 
Amberjacked said:
Hello. I am wondering if you ever resolved your issue? I am having the exact same issue with my starboard engine for the past year. I have replaced the plugs, the spin on filter, polished the fuel, replaced the fuel pump and a number of sensors all to no avail. It seems as if it is getting worse as I was out fishing and at an idle speed for an hour when the rpm started to fluctuate and the engine died. It would restart but then died again after 10 minutes. It feels like a fuel issue but when running it with a gauge the pressure is fine and no alarms come up. Starboard is a 2001 8.1 merc. Is there abother fuel filter or screen that I am missing? The dealer tells me there is an inline but my mechanic and I can not find it anywhere. Any help would be appreciated. Thanks
Click to expand...
Check the fuel pump relay socket. Mine had 1 pin heated and melted. Caused a high current draw and intermittent pump. Replaced the socket, and replaced the relay with a 14 volt over the 12 volt original. I now keep extra relays and sockets on board.
 
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