CKSNAP

I can add to your stretch. I was in a Hyundai dealership awhile back. One of the techs had a large bunch of dipsticks laying on his bench. Looked like a big bunch of yellow flowers. I inquired. If the customer complained of excessive engine noise the engine was checked with a decibel meter. Below the threshold the engine got a new dipstick and more oil to match the new higher level. Above the threshold they got a new engine. Go figure.

That’s ridiculous. Excessive rain water in the bilge could ruin your starter and cause rust and corrosion on other parts. The extra weight could damage or collapse a boat lift or trailer. A boat low in the water could get swamped. I could go on but a reasonable person can see disabling your bilge pump is not too smart.

Do not forget to test the antifreeze in the engine. Your heat exchanger could have an internal leak and dilute your coolant with raw water to the point it will freeze and destroy your engine. Easy, quick check.

After revisiting this with a couple of buddies it seems I had it wrong. The steel crank was used in the HO but only in the first 2 years of production 2001-2002. And indeed the Merc online parts manual shows a different part number for the very low serial number engines. This link from the Offshore Only website shows a thread where Ray from Raylar mentions this. See post number 9. https://www.offshoreonly.com/forums/general-q/89952-dumb-question-merc-496-mag-vs-chevy-3500hd-496-ho-truck-motor.html For those who don’t know Raylar is well known in the performance boat world as a 496 guru.

Hmmm, The question of differences between the 496 Mag and HO came up in a discussion I had with a couple friends a few years ago. One guy claimed his HO had the more exotic parts that you refer to. We checked the Merc online parts database and sampled a few serial numbers ( there are a lot). The only differences we could find between the two engines was camshaft and ECM. All other major components were the same. If there is a special bunch of 496 HO’s with these parts on them out there I’d be interested to know about it.

Make sure the throttle is opening all the way. Could be that simple.

https://www.wtvq.com/2019/06/24/ef-1-rated-tornado-caused-significant-damage-at-moors-resort-on-kentucky-lake/ Drone view. Much better video

This is the Moors Resort on Kentucky Lake last Sunday. Luckily no one was hurt. EF1 Tornado.

Mine takes about 10 qts also. Maybe somebody transplanted a pickup engine into your boat.

That's normal.

Don't waste your time drawing a diagram. Everybody has a cell phone with a camera.

Small world. I was Mobil dealer back in the 80s-90s. Remember the oil recall?

Not boat related but interesting to compare. I recently had a medium duty Diesel engine in a truck I own rebuilt. It had over 21,000 hours on it. DT466E Navistar.

Your boat lift doesn't hit potholes at 60 MPH. No need for the extra support.

Your tach should have a rotary switch on the back that changes it from 4 to six and 8 cylinders. With a screwdriver carefully move it around to all three positions several times. Then return it back to original position. This cleans the contacts and may fix your tach problem. Worked for me. Sorry can't help you with fuel sender location.