That is great to see, awesome improvement over the initial pictures. May not be a bad idea to yank your exhaust manifolds and exhaust hose and clean any remaining oil residue/build-up out of them, might help with the residual film that you saw. I'm glad you're getting it squared away, I would have left it in the garage before dealing with that mess every time out.

Awesome job by Raylar to identify the problem and resolution, great to have experts in the industry involved on the board offering advice (for free no less...).

If you have a 496, the first step would be to run your boat on the hose and let it get warm. Then give it a few revs and immediately shut it off. Then pull your plugs. If the look all brown, then you probably have an oil issue. From the GM Bulletins I have read this was only an issue in 2001-2003 496s. After 03, they switched to the new gasket. If you are able to narrow it down to the gaskets, you will need to order 10 new intake bolts for the 2004-2007 GM 8.1L vortec. These can only be ordered direct from the dealer @ $4.50 each. You will also need gasket #89017539. I was able to get it from a vendor on eBay for 1/2 of what the dealer wanted..... Unfortunately I don't have the bolt part numbers as I accidentally ordered the same ones that were already on the motor. I used them without issue, but I would go with Raylar's suggestion and order the longer ones... The OE bolts are silver and the 2004-2007 bolts are black. The gasket is only 1/2mm thicker so I just used the new OE bolts that I had ordered. Either way, I believe you have to use NEW bolts each time. Good luck!

Well today we ran about 15 miles at 3500 rpm. Took a look at the transom and there is a thin, very thin layer of soot. Looks like it is getting thinner each run

Most of the ethanol and addtive gasolines being distributed today and used will develop some soot on the transoms of performance boats where air fuel ratios are on the rich side to protect against lean burn and detonation. In your case the oil residue mixed with and top of the light regular soot was the bigger problem i would not expect a perfectly white totally unsooted transom with todays engines and fuels. The only way we get rid of the soot on our dyno is to run test fuel or race fuels that are minus these great new additives and ethanol.

Best Regards,
Ray @ Raylar

Do ethanol treatments help at all? I have been running the Lucas ethanol treatment. Also with the colder water here in MI, I may drop back down to 89 octane. With the whipple stage 2 flash, dustin suggested I run 91 minum octane...... Today we ran 92 octane. Right now the water temp. is the 60s....

Today the soot was less than yesterday :riding: which is an encouraging sign. I did another plug check today, most of the plugs look great, a few of them has slight signs of oil burn, very slight. I assume this is just the left over oil making its way through....

BUT, I have an issue...... I originally thought it was related to the intake gasket leaking, but the issue still exists. I am noticing a miss or sputtering when the boat has a 4 or more people on it when trying to plane and around half throttle. If I give it 3/4 to full throttle when planing the miss is not noticeable. Once on plane, you can nail the throttle at any rpm and it responds as normal. I originally thought it has some water in the fuel, but I put some dry gas in and have gone through at least 150 gallons since the problem began.... The motor is not going into guardian mode... Must there is a miss under heavy load at 1/2 throttle...ll. any ideas?

I've got a 2002 Baja 292 Islander with a 496HO. I noticed the oily soot at the lunch spot on the KY Lake Fun Run after running hard for 40 miles. It's not nearly as bad as yours was but its definitely from the same reason. It smeared like crazy when I went to wipe the boat down with quick detailer. I normally run with the exhaust through the prop but didn't that afternoon. It's not a major deal as of now to me so I'm going to have the gasket done over winter when I have the drive gone through and alignment checked. Big thanks for posting all the part numbers too :drink:

This doesn't sound too far different from an issue I was having recently. How long since you changed the plugs/wires/cap/rotor? I did all this and pulled my cap/rotor off. The cap was heavily corroded, the rotor was seriously worn away. The spark was having to make at least a 1/2" jump to connect. Thus...my engine was running like crap with a slight miss when I wasn't under hard acceleration. Fixed it and boom, I was back in action.

496 is distributor less.... Each cylinder has its own coil. I just put new plugs in it but wires maybe my next step...

Low-psi, we have our custom wire sets in stock, but I am not sure thats your problem. You can ohm the wires with a tester and see how they vary or read out of range. You can also fire the engine up at night in an very dark -no light background and watch for arcing and such in the dark against places where the wires run around and over metal on the engine.
You hesistation or stumbling problem could be from several things, especially from a faulty -intermittant tps sensor, possible IAC sticking, fuel pressure drop, etc. What plug number do you have in the engine? With all that oil you had in the intake, you might also want to carefully clean the MAP sensor out of any oil or residue that may have formed in it. the MAP on thse engines almost totally controls fuel mapping, delivery and timing advance.

Best Regards,
Ray @ Raylar