6v92 - One engine varying speed
Boat ran fine last time out, and no work done since other than zinc replacement. Yesterday afternoon, running both with and without the sync engaged, the port engine stayed a steady 2100, but the stbd varied from about 2050 to 2150. Any suggestions on where to start looking?
Re: 6v92 - One engine varying speed
assuming RPM was really fluctuating (not jsut the tach), how about tranny fluid level? happened to me once early on, i had let the level get too low and the tranny started slipping a little.
Re: 6v92 - One engine varying speed
I was thinking it was a fuel issue.
Re: 6v92 - One engine varying speed
Fuel. Either restriction or air in the fuel supply.
Check there first.
Re: 6v92 - One engine varying speed
It wasn't just the tach. I could hear them go out of sync. Can't imagine where air would come from all of a sudden like this, without having touched anything. I guess I'll start by changing the filters and checking for any water in the separator.
Re: 6v92 - One engine varying speed
Got vacuum gauges on the fuel systems? If so its easy to check - if the needle is bouncing you have air coming in; if the restriction is very high at full load you've got a problem in the lines somewhere (its possible some gunk got loose and against the pickup in the tank)
Spec for max restriction on suction at full load is 12 inches of mercury.
Re: 6v92 - One engine varying speed
I have vac guages. Can I check at idle, or does it have to be under load? The symptom only occurs at running speed, not at idle.
It did begin right after fueling up on Sunday, and my tanks were under a quarter at the time.
Re: 6v92 - One engine varying speed
You MIGHT detect it at idle, but you really need to look while its happening.
Gunk in the tank can move around; if it is not covering the pickup it may not happen all the time.
BTW in an extreme case it can plug up the works, stall the engine and prevent a restart! I've had it happen, and had to go find a vacuum tank that I could attach to the filter to pull the gunk through - there was no other way to clear it out, as I had no idea where it was lodged and couldn't find it in the filters itself.
The vac tank took care of it.....
Re: 6v92 - One engine varying speed
Then again....since it's the starboard engine, it could be the synchronizer or a tight cable? You could watch the throttle and throttle control cable while it's doing it's variation and learn whether the engine slows first and then the synch catches it up, or whether the engine is slowed by the synch throttling back and then up by itself.
Doug Shuman
Re: 6v92 - One engine varying speed
If the sync is turned off, it'd be pretty tough for it to be involved.... :D