Mobil 15w-50 3.0L Mercruiser Marine 40 hrs

[1 FMF]

do you think the report's fuel #'s warrant fuel pump removal and inspection? Other than that, I can think of no other source for fuel #'s other than blowby past the rings- which I can do nothing for, and compression checks out 170+psi for all cylinders

 

[Schmoe]

On these marine engines, your going to get fuel dilution. I am surprized that the oil held up so well. I guess they don't call these engines the "Iron Duke" for nothing. Just think about all that work that 4 cylinder is having to do. Simply amazing.
I'd personally would get rid of the Mercruiser oil, it just doesn't look as good as the others. That M1 15W-50 with 80 hours would surely get my vote. I too have the same engine, but a '96 (gosh, can't believe she's almost ten years old) and have some hesitation as well. May have to try what you did. However, doesn't that thick of an oil peg your oil pressure? I was using Vavoline VR-1 20W-50 and was pegging almost 80 psi at WOT.

 

[1 FMF]

the mobil 15w-50 was run this past season for 40 hours. Total hours on the engine, according to the hour meter that I installed when I got the boat, now reads 80 hours.

My oil pressure gauge always reads 40psi, but will drop to 20 at hot idle. The gauge in the dash and/or sender is not very sensitive. I've hooked up a mechanical 0-100psi pressure guage on the block and observed 40-60psi at idle to 2000 rpm, but the gauge wasn't liquid filled and the needle had a lot of flutter to it.

for that year you have the rochester carb I'm guessing. I have the mercarb on my 3.0L, but the only differences are accelerator pump and bowl sizings. They all work the same and their fuel metering circuits are all identical.
Had the same (similar) carb, rochester 2b, on my 1976 351w motor and I can remember after having that carb rebuilt there was a dead spot when giving it throttle around 1500 rpms. So this season, after buying 2 carb books and learning everything about carbs, is I came to the conclusion the rochester/merc carb manuals specify an incorrect float setting. I tried & verified 3 times the float level on my 3.0L mercarb, along with increasing the jet size and what fixed it was raising the float level like 1/4" more than what merc service manual #26 says.

[ November 23, 2004, 01:47 PM: Message edited by: 1 FMF ]

 

[Schmoe]

I've had this "problem" for a couple of years, just never got around to getting it fixed. Kind of learned to live with it. It is a Mercruiser carb. Was told by some other Merc mechanics that it could be the float, as you have mentioned, get the NAPA p/n 2-477 and replace the float. Never thought about sizing up the jets. Plugs are dark carbon, typical for rich conditions. Need to get on that problem here pretty soon.

 

[buster]

Nice report with the Mobil 1. Stick with that.

 

[Brett Miller]

Isn't the Iron Duke the GM 2.5L?

 

[1 FMF]

Boat: 2002 Bayliner 19' with 3.0L Merc I/O 130hp,
mercarb 2-barrel, 5 qt oil capacity, mobil oil filter.
Spent good part of beginning of the season tuning the carb to fix a hesitation when accelerating in the 2000 rpm range; boat had it since new. Turns out the float level spec in the service manual is wrong, so I adjusted the level way high and it accelerates great now. I also increased main jet size from stock 1.55mm to 1.65mm. Boat runs at 4000 rpm all the time for skiing. Plugs still look clean, no carbon buildup at all really, still the same light gray/tan color. Plugs are AC-MR43LTS (cold).
I also run redline lead substitute (sodium based) which is where the sodium #'s are coming from. Boat is in fresh water, so I'm positive there's no raw cooling water getting into the oil. Blackstone suggests taking a sample next time before starting engine to warm it up to help with fuel #'s. 2-3% is common for carb'd marine engines, happens from idling and slow speeds. The high 4% fuel from past analysis was from taking the sample when winterizing the engine in cold weather, carb had iced up and motor stumbled for 1/2 hour before heating up.

*** Thanks for the advice last year for going to a 50wt oil to help with lead #'s!!!

code:

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brand mobil redline merc

weight 15w-50 10w-40 25w-40

analysis Blckst Blckst Dyson

date 11/7/04 10/26/03 1/5/03

engine hours 80 37 10 (approx)

oil hours 40 27 10 (approx)

aluminum 3 8 9

chromium 1 1 1

iron 19 16 88

copper 3 7 20

lead 1 21 20

tin 3 2 33

molybdenum 58 568 12

nickel 1 0 --

manganese 0 1 --

silver 0 0 --

titanium 0 0 --

potassium 4 1 0

boron 125 13 --

silicon 21 41 152

sodium 166 101 107

calcium 2536 2601 474

magnesium 222 10 710

phosphorus 1023 1179 784

zinc 1210 1283 900

barium 0 1 --



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Vis100C 15.4 12.37 11.5

TBN 10.2 NA 11

Insol. 0.2 0.1 good

water trace 0 0

fuel 2% 4% 0

flash(F) 350 295 --

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[Terry]

Fuel is/was the issue more than vis. You are still getting a good fuel dilute impact.