This is a 1990 200 hp carbureted engine J200TXESM with an Outboard Jet lower unit.
I recently d/c'd the oiling system and am running premix temporarily (for another reason, not at all related to this), and plan to reconnect it next spring, but this problem occured before and after the D/C so I don't think it's related.
The engine starts easily, idles smoothly (for a V6) and accelerates well through the entire power band. It runs very well at normal cruising speeds (3500-4500 for me) and even seems to run perfectly up to about 5,500 RPMs. WOT is 5800 to 6000 and it still gets there.
I've recently noticed it sporadically loses about 2-300 rpms at WOT, then comes back. It will be going at 58-6000, then decrease down to 55-5700 and then back, all with corresponding change in engine tone. This isn't a huge loss in power or speed, barely noticable because the difference in speed in my boat between 5500 and 6000 is maybe a MPH. Passengers never notice it.
It's not like a regular pulse, not regular at all in terms of a rhythm, but it does regularly occur. "Regularly irregular" I guess is how I'd describe it. It doesn't seem to be related to the bite of the jet impeller in the water (which can also happen w/ an outboard jet making any turns or in anything but perfectly smooth water) but it will come and go.
If I keep it below 5500, it would never happen, and I would never notice it.
I don't recall this going on earlier in the season or last year, but can't say for sure. It's actually pretty subtle and I don't run WOT all that much.
I have a Racor water sep. filter and religiously keep the bowl drained of water.
I have not tried pumping the bulb when it happens because I haven't noticed it until recently and haven't had passengers along.
Compression and spark were recently tested and both are good. Hoses are in excellent condition and all connections seem tight.
Pulse limiter was replaced and fuel side of VRO/OMS pump was rebuilt by reputable shop this spring.
Do you think this is a potentially damaging problem or just an annoyance? My strategy so far is just not to run at WOT to avoid being annoyed and until I'm assured it's not potentially damaging (i.e. lean condition).
What would be steps to pinpoint the problem?
Do you think it might be a dirty carb problem?
Could it be a weak fuel pump, even though it was rebuilt? I really can't remember it being a problem last season, before the rebuild, but of course there was also an entire winter lay-up in that time (properly winterized, fogged, fuel stabilizer, etc.)
I recently d/c'd the oiling system and am running premix temporarily (for another reason, not at all related to this), and plan to reconnect it next spring, but this problem occured before and after the D/C so I don't think it's related.
The engine starts easily, idles smoothly (for a V6) and accelerates well through the entire power band. It runs very well at normal cruising speeds (3500-4500 for me) and even seems to run perfectly up to about 5,500 RPMs. WOT is 5800 to 6000 and it still gets there.
I've recently noticed it sporadically loses about 2-300 rpms at WOT, then comes back. It will be going at 58-6000, then decrease down to 55-5700 and then back, all with corresponding change in engine tone. This isn't a huge loss in power or speed, barely noticable because the difference in speed in my boat between 5500 and 6000 is maybe a MPH. Passengers never notice it.
It's not like a regular pulse, not regular at all in terms of a rhythm, but it does regularly occur. "Regularly irregular" I guess is how I'd describe it. It doesn't seem to be related to the bite of the jet impeller in the water (which can also happen w/ an outboard jet making any turns or in anything but perfectly smooth water) but it will come and go.
If I keep it below 5500, it would never happen, and I would never notice it.
I don't recall this going on earlier in the season or last year, but can't say for sure. It's actually pretty subtle and I don't run WOT all that much.
I have a Racor water sep. filter and religiously keep the bowl drained of water.
I have not tried pumping the bulb when it happens because I haven't noticed it until recently and haven't had passengers along.
Compression and spark were recently tested and both are good. Hoses are in excellent condition and all connections seem tight.
Pulse limiter was replaced and fuel side of VRO/OMS pump was rebuilt by reputable shop this spring.
Do you think this is a potentially damaging problem or just an annoyance? My strategy so far is just not to run at WOT to avoid being annoyed and until I'm assured it's not potentially damaging (i.e. lean condition).
What would be steps to pinpoint the problem?
Do you think it might be a dirty carb problem?
Could it be a weak fuel pump, even though it was rebuilt? I really can't remember it being a problem last season, before the rebuild, but of course there was also an entire winter lay-up in that time (properly winterized, fogged, fuel stabilizer, etc.)