2005 F115 using oil

[Just_Rob]

Hello all, I'm looking for some advice on a 2005 F115 that is using too much oil. I just bought a 2005 22' pontoon with the F115 (unknown hours) from a former boss and call him a friend. He is a maintenance supervisor and lifetime mechanic so I trusted him. He said the boat runs good, and it does. It fires right up, idles well, has good acceleration, and tops out about 25mph at 52-5300rpm. Pulls a tube about 1-2 mph slower. I checked the oil Friday before spending our first weekend with it on the lake. Oil level was middle of the hash marks. I put maybe three hours on it cruising, and then 2-3 hours pulling a tube until the low oil alarm sounded. Shut down and checked it, barely any oil on the dipstick. I added a quart and tubed for a few more hours until the low oil alarm sounded again. Dry dipstick again, loaded it up and angrily drank beer. I never saw any smoke, but after adding the quart I was paying more attention and did notice the burnt oil smell.
I ran a quick compression check on it yesterday - cold engine (my mistake but the numbers are still telling) - throttles wide open - good battery - 8 cranks each for uniformity
#1 140 & 135
#2 105 & 110
#3 110 & 112
#4 88 & 98
I could see carbon buildup on the tops of the pistons but did not scope the cylinders. I didn't do a leak down because I don't have a manual for it and not sure what to set the air pressure at, anybody know?
Picture of the plugs is attached.

Looking for advice on my best next steps, should I shock it with some ring free, change fluids (maybe heavier oil?), and check everything again including the leak down? Or just sell it while its still running good and take a little hit vs the big hit when it completely craters. I'm really just upset with myself for not checking this stuff before I handed a chunk of cash. Instantly reminded of one of my favorite quotes "Trust, but verify"

[99yam40]

shock treatment with ringfree would be my 1st

get another set of compression reading with motor warm, and record them so you have something to compare after the ringfree treatment

those reading suck for a 4 stroke

I think 90 or 100psi would be good for the leakdown, at least it will tell if rings or valves

[fairdeal]

its difficult for me to believe a little engine could "burn" that much oil in a few hours running

I would be looking for a leak
perhaps from the oil pump/driveshaft seals

[Just_Rob]

Turns out I can't get ring free locally, but I can get some BRP Engine Tuner. Does anyone have experience with this stuff or should I just order the ring free from the amazon? I'll do the leak down before and afterwards to see what I find. I agree with 99yam40, the current readings suck! I don't understand how it can run so well, minus the massive oil use, with such terrible numbers. I may also pull the lower unit to see if there is any oil leak evident there.

[Just_Rob]

Ok, she passed the compression checks with 142-150 on all cylinders. She failed the leak down. 5% on 1, 2, and 3, 45% on #4. Sounded like it was coming out of the oil filler neck. I scoped #4 at BTC and did not see any scoring. I dropped the lower unit and did not see any evidence of an oil pump leak. I did notice major carbon build up on the thrust washer behind the prop. Could a stuck ring cause this much leakage and oil use?
I'm hoping to have time to get the decarb cleaning done this week. What's the best way to decarbonize?

[99yam40]

follow the instructions on the BRP Engine Tuner if that is what you are going to use.
I never used it so am no help

[Just_Rob]

I was able to get the ring free, I was just reading on the spec sheet from yam that "Minimum SHOCK TREATMENT per engine: 3.3L to 1.7L engines - 64 treated gallons 1.6L to 700cc - 24 treated gallons 699cc and below - 12 treated gallons" that seems like a lot of fuel!

[99yam40]

I have used 2 oz to a gallon in a small tank on small motors.
running it for 15 minutes to make sure it is in all of thefuel system and motor cylinders,
turn off and let it sit overnight.
take it out and run it hard for 15 or 20 minutes and shut down again and let it sit while I fish.
and then run hard going back to the ramp.
take it home and run on hose to wash out the saltwater.

or run out on the water until all the treatment gas was run out.
take along other gas to switch to once it is all gone.

sitting in driveway after, make sure you place something under the lower unit ,as some black stuff will be dripping out of the exhaust overnight
but that was on my C40 2 stroke

normally running 1oz to 10 gallons is maybe what they were talking about as a normal treatment for a bunch of fuel

[TownsendsFJR1300]

As stated above, 2oz /gallon for SHOCK TREATMENT.

Regular use is 1oz / 10 gallons.

Something else to try is Seafoam. Seafoam is used to help dissolve carbon.

I'd tilt the engine up, bring engine to TDC (cylinder #4) with all valves closed.
Fill the cylinder covering the piston and let for a couple of days.

Once done, remove the spark plug and crank over to rid of all the Seafoam(you don't want a hydraulic lock)
Start engine, run a bit and re-test your leak down..

At a 45% leak down rate, I have to doubt any of the above will fix your issue but certainly worth a try..

.

[Just_Rob]

Is it normal to pass compression but fail a leak down? #4 had 150 compression and 45% leak down.

[TownsendsFJR1300]

Is it normal to pass compression but fail a leak down? #4 had 150 compression and 45% leak down.

Might want to re-test both the compression and leak down on that cylinder..

[Just_Rob]

The ring free worked! I ran a separate tank with 6 gallons/12 ounces of ring free. I picked up 700 rpm at WOT. I thought it may have been something with the ring free being a higher octane, but when I switched back to my main tank, I was still making 6,000 rpm. Before I was only getting 52-5300. I ran the leak down when I got it home and warmed it up again. 5-8psi on all four cylinders.

I did notice engine oil leaking from these two holes before I took it leg.jpg out to run the ring free, can someone help me out with the cause? I've read the oil pump seals are bad about leaking in these things.

[TownsendsFJR1300]

Sounds like the RF worked well with sealing but your original oil "burning/leak" is indeed, likely the lower crankshaft seal.

You couldn't find the leak as it was leaving the engine down the driveshaft directly into the water...