Devil_Inside
Petty Officer 3rd Class
- Joined
- Jun 17, 2007
- Messages
- 76
I have a 1995 Mercruiser 5.7 TBI/EFI with a Bravo III drive of the same vintage. I am going through my pre-season checks with the boat sitting on a trailer and I seem to have some sort of vibration, which is most noticeable at fast idle - 800 to 1000rpm. The vibration is present with the drive in neutral as well as in drive.
The drive was serviced by a reputable Mercruiser dealer over the winter due to a leaking input shaft seal. I am not sure if any part of the U-joints were replaced as part of the service, but at a minimum they were inspected, serviced and greased by the shop. The U-joints and input shaft yolk are not that old anyway as they were replaced a few seasons ago by a different shop due to the same problem with a leaking input shaft seal (long story).
The engine alignment was also checked by the shop at the end of last season with a proper alignment tool and everything was within spec. The engine was not disturbed in any way over the winter.
It sounds like for these sort of issues the problem is either related to the drive or ignition (misfire), but I can't decide what to try first. I can yank the drive off to see if the problem persists or not, which will prove or disprove a potential problem with the U-joints, but I am not sure if there is something easier I can try first. My gut feeling is misfire, but it is hard to tell.
From an ignition perspective, the spark plugs, wires and cap/rotor are only a year old. I took the cap and rotor off and I cleaned all the contacts. Since this engine has a "brain", do I need to place the engine in base timing mode to figure out which cylinder is misfiring? I am not sure if the engine is trying to compensate the misfire somehow making it more difficult to pinpoint the problem.
Any help would be appreciated.
The drive was serviced by a reputable Mercruiser dealer over the winter due to a leaking input shaft seal. I am not sure if any part of the U-joints were replaced as part of the service, but at a minimum they were inspected, serviced and greased by the shop. The U-joints and input shaft yolk are not that old anyway as they were replaced a few seasons ago by a different shop due to the same problem with a leaking input shaft seal (long story).
The engine alignment was also checked by the shop at the end of last season with a proper alignment tool and everything was within spec. The engine was not disturbed in any way over the winter.
It sounds like for these sort of issues the problem is either related to the drive or ignition (misfire), but I can't decide what to try first. I can yank the drive off to see if the problem persists or not, which will prove or disprove a potential problem with the U-joints, but I am not sure if there is something easier I can try first. My gut feeling is misfire, but it is hard to tell.
From an ignition perspective, the spark plugs, wires and cap/rotor are only a year old. I took the cap and rotor off and I cleaned all the contacts. Since this engine has a "brain", do I need to place the engine in base timing mode to figure out which cylinder is misfiring? I am not sure if the engine is trying to compensate the misfire somehow making it more difficult to pinpoint the problem.
Any help would be appreciated.
