Updated! Challenger 210 New impellers + wear rings, one engine rpm keeps dropping...

[rambo benson]

It's a 2010 Challenger SE 210 310 HP.
After 13 years and 500 hours, did an exhaustive backyard rebuild of everything behind the engines: Both jet pumps were completly rebuilt with OEM wear rings, new IMPROS-restored impellers, new drive shafts, all bearings, seals, anodes, steering and reverse cables.

On the water, ran smooth and great for a little while. But then, slowly accelerating past 30 mph, the Starboard engine would drop 1000 rpm every 5 seconds with mild vibration for about 5 seconds, repeatedly. And then, even at low speeds.

I was thinking the new OEM wear ring is too tight, getting rubbed too much by the restored impellor. Maybe ring can swell up and get worse. (have some bad experience there)
Don't think it's seaweed.

Does any mechanic here think the wear ring could still wear in ok?

'll get a camera in their tomorrow and by the way: There are NO trouble codes showing.

THANKS!

 

[rambo benson]

Ok here's phone cam photos. Looks quite smooth. Can't see any major burring to slow the prop. Also can see a tight thin line of light around the outer edges.

A friend suggests the problem could be a sparkplug, injector rail sucking air through a leak, or a bad injector. But wouldn't any of those throw trouble codes and/or limp home mode?
(Still no codes)

I'm replacing sparkplugs today and will report back. Please chime in any thoughts in meantime!
THANKS

 

[rambo benson]

Lots of Crazy windy weather, too rough to test yet after plugs were changed.
See photo. Fairly new plugs look a bit fouled, but wet as I pulled them out. That's a drop of oil in the gap on left plug.

Because there was oil sitting in the spark plug tunnels on top of heads. See rubber connectors. Both engines!

I think it's from when I left oil caps off spattering oil over engines one day. Or a clumsy spill when changing oil. Neither engine smokes at all. I don't know how else oil could get on top of the heads but by a spill....anybody?

Weird, I had snugged those plugs very well when new a couple years ago. But they were practically loose. Didn't really need a wrench, just extension to turn them. Maybe heat and cooling cycles sucked sitting oil down into threads, eventually loosening them?

Could have lost ground intermittently I guess.

Weather improves tomorrow, will try a run!

Friend suggests changing fuel filter/ seperators too.
Thanks!

 

[rambo benson]

Getting closer! Ran fine for 30 minutes except other side engine began missing. A coil had popped off. (I had really pressed it on good too)

So pressed it back on, and ran fair, but almost imperceptible slowing/vibration. Top speed dropped a couple mph.

Do coils sometimes wear out where they grip the spark plug top post? Still no codes, would it throw codes?

Next I'm also changing that engines plugs today.
Kinda tight on money, ya think fuel filters or coils next? (500 hours, several services, always ran additive in fuel)

No one has been commenting, am I just too wordy? Wife thinks I am!

Thanks...

 

[rambo benson]

All is well! Ater new plugs, cleaning and regreasing coil sticks, both engines run smooth and strong.

(On top of CRC spraying every connector, previous solenoid, relay and fuse replacements before that didn't completely solve intermittent RPM drop)

Still wonder how oil got down in spark plug tubes Is there a head gasket around the plug area?

Otherwise someone must have spilled it in there.