My Dad has boat with a 2005 Volvo Penta 5.7 GXI motor with around 170 hours on it, that has, for lack of any other way to put it, been nothing but trouble since he's owned it. He bought the boat in 2008 with 8 hours on the motor.
The main problem is that is has a tendency to run very well on the outward leg of a trip. However, usually after sitting over night or at least several hours it won't start. Typically when it won't start, it cranks over, has spark (visual confirmation, however haven't checked all cylinders at once), and is getting fuel into the cylinders (plugs are wet and pump is pumping fuel). The ECM isn't throwing any codes either, we have the diagnostic program and all the parameters appear normal.
It has done this three or four times now, and trolling back from Hinchinbrook and Montague is getting old. Every time it has done this he has replaced a sensor or wire, etc and it has eventually run, each time convincing us that was the problem. After trolling in yet again last week, I am wondering if there is something else going on and it just runs again after sitting for a while, coincidental to replacing the sensors. When it runs it always runs flawlessly, and upon shut down gives no indication of a problem.
The motor was professionally installed by a shop in Juneau. We have run the diagnostics software, followed the appropriate flow chart in the manual, changed the plugs, changed numerous sensors, replaced the batteries, checked and re-crimped the battery leads and connections, added a fuel primer bulb (which is always pumped prior to a cold start), charged the batteries, and checked the fuses. I'm starting to think maybe there is a problem with the ECM itself? We are running out of things to check, change, and look at. Any ideas?