Diesel in the crank case for cleaning?
 

Has anyone heard of this or tried it?

I just go a new to me Jet boat. It's a 21ft 1979 Rogers with a 454 BBC. "has been sitting for 2 years" last tags say 2016, so my guess it even longer.
I have to change the oil, it is oily but has that smell of old oil and the feel of the oil is less that great.
I was told to put some diesel in the crank case, run it for 5-10 minutes then drain it and fill with good oil. I will be ordering a filter relocation kit, not sure how I'm going to get it out without dumping oil in the bilge

my other issues is draining it... this boat doesn't have the drain hose (i cant find it) It was suggested to pull the pressure sender unit put a fitting and clear hose on it then start it till the oil comes out then kill it. Running the pan empty like that goes against everything I know. unplugging the HEI coil and cranking it seems like a safer option..

Suck the oil out through dipstick. Just run some cheap oil in it for an hour or so and then change it again. Diesel works for pickling engines, but I would not run an engine using it.

I have heard of pouring diesel into the crankcase to wash down any contaminants that may be in the motor but not start it. Just drain it. I would run it with cheap oil and drain it after a few minutes.
I would pull the motor and install a drain line on the oil pan.
I have a jet boat as well with a remote filter and just put some paper towels under the oil filter. Just be careful not to tilt it.

I've seen where they have taken out a quart and added 1/2- 1 quart of diesel and spun the engine over after it sunk and became a milkshake. Running the engine isn't a good idea for long as you are washing down the cylinders and bearings.

Either way you are into at least 2-3+ oil changes - either to get the oil oil out or to get the diesel residue

That is an Old Timer’s trick. I have done it before. It was years ago on and old car I bought that was full of sludge. It does a great job but you only want to add about two quarts of diesel after you remove about two quarts of oil. You can also use ATF. Although I have done the diesel and the ATF trick and had good luck, the guys on here may know way more than me. Also if you do decide to do this do not rev the engine. The diesel is cleaning more than lubricating. The oil will come out black as coal.

I have used kerosene to flush things.
Never ran with it in though.
Always drained, changed oil for short run, and changed again shortly after.
Just like everyone here mentioned too.

I hear fear, but do not see any yet. What am I missing ?

I had a flood in my shop 2 years ago and everything under 3' was underwater. We pull drains and filled all the crankcases up with diesel until we could work our way around to doing them right. Never started any, but did roll them over to get water out. Drained diesel, two rounds of CHEAP motor oil and filters, started, and watched for milkshakes. No problem, then fill with synthetic and good filter. ALL survived just fine!

dont know about that boat but on my last jet boat I could have the engine out in about 30 minutes if I was lazy. if you are that worried about it just pull the engine, drop the pan and clean it out and then add a drain hose to the pan.

Old boss loaned me his 6cyl Ford truck to haul some wood. Said if I could fix the knocking I could keep it for a couple weeks. Called my Dad, who was a diesel mech at one time. Let him listen to it over the phone. Told me it had 2 stuck lifters from no maintenance. Checked the oil, down a quart, put in one quart of diesel fuel, ran it 200 miles to my home town and back, picked up the wood and changed the oil 2x afterwards. Took it back to my boss, he wanted to know what I did, I told him my old man fixed it. Also, told him to change the oil more often. He kept that old truck as his beater and still had it when he retired several years later. Went to his estate sale after he passed, truck was in the sale. Sold to first bidder and he drove it off. It is probably dead by now, that was 30 years ago. LOL ! Not sure I would do that again, but it worked.