Hi, this is my first time thread and I am hoping that someone can help with some good advice as I am at wits end
Have a 2008 Mag 496 DTS with about 70 hours on the clock, repowering an early model 30 foot Fjord. I bought the boat two years ago and it hasn’t run right since. First problem was running way too rich. Heaps of black soot on water. The mechanic spent weeks trying to figure it out. Eventually discovered it was a gradual build up of fuel pressure due to a micro screen disc filter (or something like that) that was getting blocked. He removed this and the running rich was finally fixed. He said that Volvos had a similar problem and it was ok to remove the disc as there was still a filter in the pump.
Since around that time, I have had an annoying intermittent problem. The engine starts first time every time and purrs like a kitten. I let it warm up for about 5 minutes as this tends to lessen the problem. When I pull away from the dock it runs rough for usually for about 3 to 5 minutes and then comes good. This occurs at around 1100 to 1800 revs. It seems to go away completely after the engine has been run for a while. This is the case on almost every occasion, although it may run rough for only a minute or on my last trip on and off for half an hour which is the most it has done so. Was ok at 1800 revs but started to run rough when throttled back to 1400
Here’s the weird thing. It seems to be worst after the boat has been sitting for a week. If I go out today, it will run rough as described above but the problems not there the next day. For this reason it has been a little hard for the mechanic to pin point the problem. We have changed both the MAP sensor and the IAT sensor along with fitting an external fuel filter and water separator. The mechanic doesn’t seem to think it’s a fuel problem as it is intermittent. Put some fuel stabiliser in before my last trip, doubt that’s connected to the problem increasing, suspect it is just co-incidence
I have put up with it as we just put it down to the engine being temperamental but something is wrong . AAARRGHH
Have a 2008 Mag 496 DTS with about 70 hours on the clock, repowering an early model 30 foot Fjord. I bought the boat two years ago and it hasn’t run right since. First problem was running way too rich. Heaps of black soot on water. The mechanic spent weeks trying to figure it out. Eventually discovered it was a gradual build up of fuel pressure due to a micro screen disc filter (or something like that) that was getting blocked. He removed this and the running rich was finally fixed. He said that Volvos had a similar problem and it was ok to remove the disc as there was still a filter in the pump.
Since around that time, I have had an annoying intermittent problem. The engine starts first time every time and purrs like a kitten. I let it warm up for about 5 minutes as this tends to lessen the problem. When I pull away from the dock it runs rough for usually for about 3 to 5 minutes and then comes good. This occurs at around 1100 to 1800 revs. It seems to go away completely after the engine has been run for a while. This is the case on almost every occasion, although it may run rough for only a minute or on my last trip on and off for half an hour which is the most it has done so. Was ok at 1800 revs but started to run rough when throttled back to 1400
Here’s the weird thing. It seems to be worst after the boat has been sitting for a week. If I go out today, it will run rough as described above but the problems not there the next day. For this reason it has been a little hard for the mechanic to pin point the problem. We have changed both the MAP sensor and the IAT sensor along with fitting an external fuel filter and water separator. The mechanic doesn’t seem to think it’s a fuel problem as it is intermittent. Put some fuel stabiliser in before my last trip, doubt that’s connected to the problem increasing, suspect it is just co-incidence
I have put up with it as we just put it down to the engine being temperamental but something is wrong . AAARRGHH
