496 HO. Lul in RPM...

[slingingsmoke]

I'll be cruising between 3000 RPM and the motor will lul down to 2700 RPM. It'll do this back and forth. If I slow down to 2700 RPM it will lul up to 3000 RPM. What gives???? Its a 496 HO w/ a "X" drive spinning a 26P 4-blade.
Does the drive have anything that "slips" like a tranny converter???
any help will do..Thanks

[Beer-30]

There is a "coupler" that can become stripped, but usually will just not transfer any power at all to the drive input shaft.
Does it idle normal? Any surge at idle? Any misfiring or roughness? Almost sounds like a spark plug or wire going away. Also sounds like dirty injectors. Water in the fuel? Have you changed the fuel filter recently?
I would start with a fresh fuel filter and then some real good performance injector cleaner like Lucas or RedLine - for a few tanks. We did this on a friends 2003 HO that was running rough all around. It didn't really change much and ended up being a few fouled plugs.
REALLY sounds like dirty injectors or water in the fuel - to me.
And, ONLY 87 octane. I run mine on 87 AM/PM (usually, but whatever is the cheapest) and have had not one problem. The engine has been dyno'd with 87 and 92 and didn't make even 1 hp more with higher octane. It can even run WORSE, as the timing never finds it's optimal point with the higher fuel.

[slingingsmoke]

It only happens at that particular RPM range... however I've lost about 5 mph on the top end. It idles fine. However, I did get a about a tank full of fuel from Super fuel at Havasu last month. I've used Costco gas here in Bako for the last run. Plugs are a few months old, but that doesn't mean they cant be fouled. I only use 87. 92 doesnt do anything but soot up the transom. I'll have to prolly pull a plug and check it out. New filters for sure.

[slingingsmoke]

[QUOTE=Beer-30;2962997]There is a "coupler" that can become stripped, but usually will just not transfer any power at all to the drive input shaft. QUOTE]
can u send me a pic of the coupler and what to look for? I'll check out the manual and see if i can find anything.

[Beer-30]

can u send me a pic of the coupler and what to look for? I'll check out the manual and see if i can find anything.
Yes, but it won't do much good at this point. You could only see it if you pull the motor. I don't think that is your problem. There would be a few additional symptoms.
The coupler is the small, round object spinning around on the BACK of this 496. When the camera comes around to the back side, you can see it spinning. Looks like a tiny torque converter with an opening for the drive input shaft: http://media.putfile.com/Bents-Nordic-Engine
SuperFuel - I was told specifically to stay away from there. They get junk fuel. A local (Havasu) mechanic told us to steer clear of that place when we were dealing with the aforementioned 2003 HO problem. That may very well be your problem.

[Aluminum Squirt]

Hey SS, way off topic but how fast are you spinning that 26P and in what boat? I'm trying to spin a 26P with the exact same set-up in a 21' Essex Sterling (pretty damn heavy) and I keep thinking I'm over propped. I'm maybe spinning 4800 with a light load, more like 4500. It's not very snappy out of the whole and for skiing so I was thinking about dropping to a 24P. Any thoughts? Again sorry for the thread highjack-Aluminum Squirt

[Beer-30]

26 is alot of prop for an HO. I spin a 24 at 5000 at about 62 mph. Granted, I have a heavy boat, but there is no way I would swing a 26 right now.

[Aluminum Squirt]

ya, I've had a feeling for awhile I was swinging too big a prop. It was my fault, I made Essex promise that if I upgraded to an HO that I would be able to hit 70MPH. Well I can do it with about 2 gallons on board and the planets alligned just right, but its pretty slow getting there. Anyway, 70MPH isn't that big a deal to me anymore and it would make a lot more sense to swing a 24" and be able to have some quickness and pull skiiers better. Since this is now a thread hijacking in progress, I may-as-well ask another question, would a 22" be too small? I know I know, borrow one and try it. Any input?-Aluminum Squirt

[Beer-30]

I have a 24 on there now and a 22 as spare. The 22 runs GREAT and will just tap the limiter. Bad on fuel, though. Tanks run dry a great deal quicker. 24 B-1 is a great all around prop for an HO.

[slingingsmoke]

have been on duty the past few days. Won't be able to work on her till monday. I'm gonna change fuel filters and replace the screen filter. I'm also gonna pull a plug or two and make sure I'm not fouling any.
The Labbed SS 26P gives me about 56-58 mph @ 4000 rpm with two coolers/ 1beer/1food, me, wifey, baby, and two friends, and the nose and ski locker full of junk. The SS non labbed 24P is about 52-54 at same RPM.